Dairy Farm Methane Capture: Californian Dairy Farms Harnessing Biogas for a Greener Future!

Read how California’s Dairy Farms are using biogas (methane) to improve the environment using Dairy Farm Methane Capture technology.

Dairy farms are known to contribute to global methane emissions, an issue posing environmental challenges. With cows producing about 11% of greenhouse gas emissions each year, tackling this problem can seem daunting.

This blog post uncovers ways on how you can turn waste into wealth by capturing and utilizing this potent gas. Ready for a cleaner, greener future? Let’s dive in!

How Dairy Farms are Cashing In on Methane Capture

Dairy farms are benefitting financially from methane capture, taking advantage of the cleaner fuel push in California and saving on diesel costs by harvesting methane.

Benefits of methane capture

Methane capture brings great good to dairy farms. The bosses can turn cow waste into money. They use a tool called a dairy digester. This tool turns waste into biogas, a type of power.

Farms can make their own power now! Also, they help save the Earth by lowering the gas that heats the planet. Such gases from farms are 11% of all in the U.S.A. each year! The state leaders in California have wanted more farms to do this job too since 2015.

Besides making power, these tools stop bad air from passing into our sky and keep us safe.

California’s push for cleaner fuel

California has been at the forefront of pushing for cleaner fuel options, and this includes a focus on reducing methane emissions from dairy farms. The state has been supporting dairy farmers in implementing methane capture technology since 2015.

Methane is a potent greenhouse gas that contributes to climate change, and it is produced by both cows through enteric fermentation and manure storage. By capturing and utilizing methane from dairy farms, California aims to reduce its carbon footprint and improve air quality.

This push for cleaner fuel not only benefits the environment but also provides financial incentives for farmers as they can turn their manure into a source of income through biogas production.

Image with ext: "Dairy Farm Methane Capture Harness Biogas".

How a dairy is harvesting methane to save on diesel costs

One example of how a dairy is using methane capture to save on diesel costs is by utilizing a dairy digester. This technology helps prevent methane from manure storage lagoons from being released into the atmosphere, reducing greenhouse gas emissions.

The captured methane can then be converted into biogas, which can be used to generate power for the farm. By relying on biogas instead of diesel fuel, the dairy can significantly cut down its operating costs while also reducing its carbon footprint.

It’s a win-win situation that benefits both the environment and the financial bottom line of the dairy farm.

Capturing and Using Methane

Cow management changes include altering feeding practices and optimizing nutrition to reduce enteric methane emissions. The methane harvesting process involves collecting manure in a dairy digester, where anaerobic digestion occurs to produce biogas.

This biogas can then be used for power generation or converted into renewable natural gas for various applications, reducing operating costs and carbon footprint.

Cow management changes

To reduce methane emissions from dairy farms, certain changes in cow management can be implemented:

  1. Adjusting feed: Providing cows with a balanced diet that includes high-quality forages can help reduce enteric methane emissions.
  2. Managing grazing practices: Implementing rotational grazing systems and optimizing pasture utilization can help minimize methane emissions from cattle.
  3. Improving rumen health: Ensuring proper nutrition and feeding practices, such as avoiding overfeeding or underfeeding, can contribute to better rumen health and reduced methane production.
  4. Breeding for low-emission genetics: Selecting breeding stock based on their genetic potential to produce less methane can help in reducing overall emissions from the herd.
  5. Monitoring and health management: Regularly monitoring cow health and implementing preventive measures for gastrointestinal diseases can minimize methane emissions.
  6. Employee training and awareness: Educating farm staff about the importance of methane reduction strategies and providing training on best practices for cow management can encourage effective implementation.

Methane harvesting process

Dairy farms can harvest methane from manure using a process called anaerobic digestion. Here’s how it works:

  • Manure is collected from the cows and stored in a covered lagoon or tank.
  • Inside the lagoon, bacteria break down the manure in the absence of oxygen, producing methane gas.
  • The methane gas is then captured and stored in a biogas digester.
  • In the digester, the methane is separated from other gases and impurities.
  • The purified methane can be used as a renewable energy source for heating, electricity generation, or even fueling vehicles.
  • Any remaining byproducts of the digestion process can be used as fertilizer on the farm.

Financial returns and compromises

Implementing methane capture technology on dairy farms can bring both financial returns and compromises. On the positive side, capturing methane from manure can help farmers generate additional income by converting it into biogas for energy production.

This means they can save on operating costs, such as diesel fuel for tractors or power generation. Additionally, farmers may receive pollution-reduction credits for their efforts in reducing greenhouse gas emissions.

However, there are also compromises to consider. The initial investment in methane capture technology and ongoing maintenance costs can be significant. It may require changes in cow management practices and infrastructure upgrades on the farm.

Innovative Solutions to Reduce Methane Emissions

– Varietal selection focuses on breeding cows that produce less methane, reducing emissions at the source.

– Genetics and data sharing allow for the identification of genetic markers associated with lower methane emissions, aiding in selective breeding efforts.

– Monitoring calves’ diet and health can help identify potential sources of increased methane production and implement management strategies to reduce emissions.

– Incentivising and rewarding farm staff for implementing methane reduction practices can encourage the widespread adoption of sustainable farming methods.

– Exploring alternative energy sources, such as solar or wind power, can help reduce reliance on fossil fuels for powering dairy operations.

Read more about these innovative solutions to reduce methane emissions in the dairy industry.

Varietal selection

Choosing the right type of cows can play a significant role in reducing methane emissions on dairy farms. Farmers can select varieties that have lower methane production rates, helping to minimize their carbon footprint.

This means considering genetics and breeding programs that prioritize animals with reduced enteric methane emissions. By using varietal selection strategies, farmers can contribute to sustainable dairy farming practices and help mitigate climate change by reducing greenhouse gas emissions from cow manure.

Genetics and data sharing

Genetics and data sharing play a crucial role in reducing methane emissions from dairy farms. By studying the genetic makeup of cows, researchers can identify which traits are associated with higher or lower methane production.

This information can help farmers select breeding stock that produces less methane, ultimately reducing emissions from enteric fermentation. Additionally, sharing data on best practices for methane reduction allows farmers to learn from one another and implement effective strategies on their own farms.

Collaboration and information exchange are key to finding innovative solutions and making meaningful progress towards sustainable dairy farming.

Monitoring calves

Monitoring the health and well-being of calves is essential for sustainable dairy farming. Here are some innovative ways to monitor calves:

  1. Use wearable devices: Track the activity levels and behavior of calves using wearable technology. This helps identify any signs of illness or distress early on.
  2. Implement remote monitoring systems: Install cameras in calf housing areas to remotely monitor their behavior and detect any abnormality in real-time.
  3. Utilize data analytics: Analyze data collected from monitoring systems to identify patterns and trends in calf health, allowing for timely interventions when needed.
  4. Train farm staff: Provide training to farm staff on calf monitoring techniques, such as observing feeding behavior, body condition scoring, and recognizing signs of disease.
  5. Collaborate with veterinarians: Work closely with veterinarians to develop standardized protocols for calf monitoring and receive guidance on best practices.
  6. Incorporate genetic information: Consider genetic markers that indicate calf health and resistance to diseases when selecting breeding stock.
  7. Foster a culture of care: Encourage farm staff to develop relationships with the calves, fostering a caring environment that promotes their well-being.
  8. Regular veterinary check-ups: Schedule routine veterinary visits for comprehensive health evaluations and vaccinations, ensuring early detection of any potential issues.
  9. Monitor feeding practices: Keep track of feeding schedules, milk quality, and quantity provided to each calf to ensure optimal nutrition and growth.
  10. Implement biosecurity measures: Follow strict biosecurity protocols to minimize the risk of disease transmission among calves.

Incentivise and reward farm staff

Farm staff play a crucial role in implementing methane capture technology on dairy farms. By incentivizing and rewarding their efforts, we can motivate them to actively participate in these sustainability practices.

This can include providing financial incentives or recognition for their contributions towards reducing greenhouse gas emissions and improving air quality. By involving farm staff in the process and valuing their efforts, we can create a collaborative culture that supports the adoption of methane capture technology across the agricultural sector.

Alternative energy sources

Dairy farms are exploring alternative energy sources to reduce their carbon footprint and reliance on traditional fuels. One option is using the biogas produced by methane digesters, which can be converted into renewable energy for power generation.

This helps farms reduce operating costs by lowering diesel fuel consumption for tractors and other equipment. Additionally, it contributes to a cleaner environment by reducing methane emissions from cow manure.

By adopting alternative energy sources, dairy farms can not only mitigate climate change but also create a more sustainable future for the industry.


Dairy farms are embracing methane capture technology to reduce greenhouse gas emissions and improve air quality. By capturing methane from cow manure, farmers can not only help combat climate change but also turn this waste into a valuable source of income.

With the support of government initiatives and innovative solutions, dairy farms are cashing in on methane capture while prioritizing sustainability for a greener future.


1. What is Dairy Farm Methane Capture?

Dairy Farm Methane Capture is a way to reduce emissions from cow burps. It also helps in pollution reduction and cuts down on the dairy industry’s greenhouse gas emissions.

2. How does it help with Manure Management?

The capture of methane involves changes in manure management. The slurry or livestock manure undergoes anaerobic digestion in biodigesters, turning it into biogas.

3. Can Dairy Farm Methane Capture be used as Tractor fuel?

Yes, the biogas produced from dairy waste via this method can serve as tractor fuel, adding another benefit to implementing methane abatement strategies for dairy farming.

4. What changes does it bring about to carbon footprint?

By capturing and controlling methane released from cows and using them productively, there is a significant decrease in both cow emissions & overall carbon footprint impact tied up with the dairy sector.

5. Does every farm need Dairy Farm Methane Mitigation?

It would be great if all farms adopt such practices but depending upon the size and capabilities of each farm, they may decide their own specific plan for handling Cow methane emissions effectively.

The Benefits of 3B’s – Biogas and Biochar from Biomass

Here’s why the benefits of biogas and biochar from biomass are absolutely a topic you should take notice of.

Are you looking for a way to harness the power of renewable energy while also reducing your carbon footprint? Look no further than biogas and biochar!

These two powerful tools derived from biomass offer a multitude of benefits, both for the environment and for your bottom line.

With biogas, you can generate electricity and heat while also reducing waste and greenhouse gas emissions. And with biochar, you can improve soil fertility and sequester carbon, all while creating a valuable byproduct.

So what are you waiting for? Let’s dive into the benefits of biogas and biochar, and discover how they can transform your business and your impact on the world.

Converting Biomass to Biochar

Converting biomass to biochar is a crucial process for sustainable agriculture and forestry.

Biochar is a highly porous charcoal-like substance that is produced by slow pyrolysis of biomass. It is a stable carbon-rich material that has the potential to improve soil fertility, enhance plant growth, and reduce greenhouse gas emissions.

The process of converting biomass to biochar involves heating biomass at high temperatures in the absence of oxygen, which results in the release of volatile organic compounds, leaving behind a solid residue known as biochar.

The process of biochar production not only produces a valuable socio-economic product but also provides an opportunity to reduce carbon emissions and mitigate the impacts of climate change.

The use of biochar in agricultural practices has been shown to significantly increase crop yield, nutrient retention, and water-holding capacity of soils. Additionally, biochar is capable of sequestering carbon dioxide in soil for hundreds or even thousands of years, making it an effective tool for carbon capture and storage. Overall, the conversion of biomass is very high and higher than for anaerobic digestion.

Keeping the Carbon Fertility of the Soil

Keeping the carbon fertility of the soil is essential for the growth and production of plants. Carbon fertility refers to the level of carbon in the soil and its ability to support the growth of plants. The carbon acts as a binding agent, holding the soil particles together and retaining nutrients for the plants to access.

However, human activities, such as deforestation, agriculture, and industrialization, have disrupted the natural carbon cycle, leading to soil degradation and loss of fertility. To maintain and enhance the carbon fertility of the soil, sustainable land management practices should be adopted.

These include reducing soil disturbance, planting cover crops, practicing crop rotation, and increasing organic matter inputs. By doing so, the carbon content of the soil can be increased, leading to improved soil structure, water retention, and nutrient availability. Furthermore, increasing carbon sequestration in the soil can contribute to mitigating climate change by reducing the amount of carbon dioxide in the atmosphere.

Image has text: "Benefits of Biogas and Biochar from Biomass".

Unlocking the Potential of Agriculture: Harnessing Biogas and Biochar to Reduce Emissions

Agriculture has always been a significant contributor to global emissions. However, by harnessing the potential of biogas and biochar, we can significantly reduce these emissions while also increasing agricultural productivity. Biogas, which is produced by the anaerobic digestion of organic matter, is an environmentally friendly energy source that has the potential to replace fossil fuels. This biogas can be used for cooking, heating, and even for generating electricity.

Additionally, the organic matter left over after digestion can be used to create biochar. Biochar is a stable form of carbon that can improve soil health and fertility, helping farmers to grow crops more effectively.

By using both biogas and biochar, farmers can also reduce the amount of methane released into the atmosphere. Methane is a potent greenhouse gas that contributes significantly to climate change. By using anaerobic digestion technology, we can capture methane before it is released into the atmosphere, producing biogas instead.

Turning Manure into Green Solutions

Biogas and Biochar for Carbon Sequestration and Soil Fertility

As the world continues to grapple with the challenge of climate change, finding sustainable solutions that can help reduce greenhouse gas emissions has become a top priority. One such solution is the use of biogas and biochar from manure as tools for carbon sequestration and soil fertility.

Biogas is a renewable energy source produced through the anaerobic digestion of organic matter, while biochar is a soil amendment made from burned organic matter. Through a process called pyrolysis, treated manure can be converted into biochar, which is rich in carbon and other nutrients that plants need to grow.

Help reduce methane emissions!

Furthermore, the production of biogas from manure can help reduce methane emissions, which is a potent greenhouse gas. By converting manure into these green solutions, farmers and other landowners can not only reduce their carbon footprint but also increase the fertility of their soil, improving crop yields and the overall sustainability of agricultural systems.

The production of biogas and biochar can provide renewable energy and soil enrichment while reducing greenhouse gas emissions.


Biogas and biochar are two powerful tools derived from biomass that offer numerous benefits to both the environment and businesses.

Biogas is generated through the anaerobic digestion of organic matter and can be used to produce electricity and heat while also reducing waste and greenhouse gas emissions.

Biochar, on the other hand, is a carbon-rich material produced through the pyrolysis of biomass that can improve soil fertility and sequester carbon, making it a valuable byproduct. By harnessing the power of these two technologies, businesses can reduce their carbon footprint and improve their bottom line.

Benefits of Biogas:

Biogas offers a wide range of benefits, including the reduction of waste and greenhouse gas emissions, the production of renewable energy, and the potential for cost savings. By diverting organic waste from landfills and using it to generate biogas, businesses can significantly reduce their environmental impact while also producing a valuable source of renewable energy. Biogas can also be used to produce heat and power, which can lead to cost savings for businesses.

Benefits of Biochar:

Biochar also offers numerous benefits, including the improvement of soil fertility, the sequestration of carbon, and the potential for revenue generation.

By adding biochar to soil, businesses can improve its fertility, which can lead to increased crop yields and improved plant health.

Additionally, biochar has the potential to sequester carbon for centuries, making it an important tool for combating climate change.

Finally, biochar can also be sold as a valuable byproduct, creating a new revenue stream for businesses.


Biogas and biochar are two powerful tools that offer numerous benefits for businesses looking to reduce their environmental impact while also improving their bottom line.

By harnessing the power of these technologies, businesses can reduce waste and greenhouse gas emissions, produce renewable energy, improve soil fertility, sequester carbon, and even generate new sources of revenue.

As we continue to face the challenges of climate change, it is essential that businesses explore new and innovative ways to reduce their environmental impact, and biogas and biochar offer an exciting opportunity to do just that.

Image source: (CC0) Biochar in the hand Simon Dooley via Flckr

Drying Digestate From Biogas Plants – Fertiliser Advances and Benefits

Drying digestate from biogas plants has major benefits. In the advanced TEMA Process™ the residual waste after digestion (solid and fibrous portion of the digestate slurry) is dewatered to 70-75% MC (MC = Moisture Content) followed by fluidised bed thermal drying, using waste heat from the biogas CHP heat exchangers.

The liquid portion which is drained away first during screening in a filter-press or a digestate separator is already a valuable fertiliser. The digestate liquid is close to 95% water and is used on-farm where it is produced and is sold locally to other farms (subject to local regulations regarding such as the Animal By-products Regs., the presence of heavy metals, and crop benefit requirements).

Advances in Digestate Drying Mean that Making Natural Renewable Fertiliser has Become Very Viable

More efficient processes have been developed to extract the maximum benefit from Municipal Solid Waste (MSW) and organic waste as the world becomes more focused on recycling waste materials.

The Dutch company TEMA Process offers fluid bed dryers for the following applications:

  • making a granular fertiliser from digestate
  • increasing the calorific value and stability of RDF (Refuse Derived Fuel), biomass, and sludge.

They do this as experts with extensive experience in the design and supply of tailored solutions for the drying of bulk materials.

Tema Process fluid bed dryers can operate at relatively low drying air temperatures, waste heat from co-gen sets, boilers, or other sources is their preferred energy source for dryer heating.

Image text: "Drying digestate from biogas plants".

The Benefits of Drying Digestate

Drying creates an odourless dry fertilizer that can be applied to crops. The dried material is light and compact. This significantly reduces storage and transportation costs. Secondly, once dried the digestate can be stored to be used when it is needed for crop growth at any time of the year.

Drying digestate from biogas plants can be accomplished using a variety of energy sources in addition to the waste gas engine jacket heat or waste heat from a combined heat and power unit (CHP). In many cases, solar energy, or exhaust air from a microturbine are used to dry the digestate.  On rare occasions, waste biogas plant heat may also be converted into electricity and directed to the process of digestate drying. However, as this is usually done more to maximise the sale of green energy for tax break reasons it is not a technically-recommended option.

During drying, digestates emit ammonia gas. This is an air pollutant but can be put through a water-stripper to remove it from the dryer off-gas to make a futher nitrogen fertiliser product.

Digestate Dryers in Use Today

Currently, approximately 500-700 digestate dryers are in use in Germany. This technology meets strict EU regulations while producing transportable and storable fertilizer. In addition, the process reduces emissions when compared to land spreading of the mixed wet digestate. It also meets the strict hygienic standards required by the EU. The end result is a biogas fertilizer that emits significantly less ammonia than moisture.

Digestate Drying Solves Past Problems

A growing number of biogas plants have been built across the world and are an important source of revenue for many farmers. However, this technology has until now had serious drawbacks. First of all, digestates have a high amount of ammonia, and they can be difficult to separate into liquid and solid fractions. The second problem was storage space for the wet materials and the lack of availability of farmland spreading space, all year round, due to run-off causing water pollution.

Too much digestate spreading on any one area is counterproductive, and great care must be taken to avoid run-off resulting in the nearby rivers and/or groundwater pollution.

Drying digestate from biogas plants is a good way to combat these problems and makes the AD process yet more efficient and environmentally friendly.

How Drying Creates Added-Value

Another benefit of drying digestate from biogas plants is that it creates added value as a product. The dried digestate fertiliser product has a far wider market and is a highly valuable fertilizer. This material can be stored for long periods and has a high dry matter content of 85% to 90%.

The dried digestate is also easy to transport and can be spread over larger areas than when in liquid form. Furthermore, it is better accepted by local communities because it does not cause a significant risk of contaminating the environment or causing river and groundwater pollution which is damaging agricultural areas globally.

Many biogas plants, in operation now, can generate up to 10,000 tons of digestate per year. The digestate from these plants is mainly used as liquid fertilizer and, until now, only a minor part was dried in a hybrid waste-heat or solar dryer.

But, there are signs that this will rise rapidly. The change will be rapid now that low-energy consumption CHP heated digestate drying technology is available. The driving forces behind this development are:

  • the high cost of energy which has meant that fossil-fuel/ mineral fertilisers have risen dramatically in price
  • the war in Ukraine which has led to shortages in the supply of the natural gas needed for mineral fertiliser production, and
  • shortages of mineral mined/chemical fertilisers due to factories closing.

Why Stop at Belt Dryer Dewatering?

A high-performance belt dryer can be used to produce a solid and easier-to-handle fertiliser alone.

Systems are available that are suitable for drying up to 100 tons of digestate per day and can reduce sludge storage space substantially. Additionally, a belt drying system can be cost-effective, enabling operators to save hundreds of Euros a day and in jurisdictions of subsidy for renewable heat production receive a CHP RHI bonus.

Many biogas plant operators go no further. However, the dried product is far more in demand and will only rise in popularity.


A high-quality digestate dryer can turn an organic waste which would cost in excess of $100/tonne to dispose of to landfill or incineration into a valuable fertiliser commodity. Drying digestate from biogas plants can be profitable if the right methods are followed.

More information is available from TEMA PROCESS

Food Waste Depackaging Systems Also Suitable for Biodegradable Municipal Waste

There is an increasing range of that are also suitable for non-source-separated biodegradable municipal waste (BMW). The trend now being to raise organic waste recycling to ever-higher percentages to both avoid this material going to landfill and to comply with the COP26 pledges made by so many nations to decarbonise their economies.

The purity of source-separated organics (SSO) is always going to be less than 100%, and in certain circumstances much less, regardless of how well-trained personnel are in source separation of food wastes.

Packaging is mechanically separated from organic waste in these systems. The packaging is collected and feeds a compactor and is disposed of, or if possible, it is recycled. Organic waste is either collected in tankers or goes directly into a digester or is used in composting facilities.

The best Food Waste Depackaging Systems reliably and quickly separate organic from non-organic packaging materials, including packaging materials such as plastics and paper. They are ideal for converting waste from the food processing industry, supermarket and restaurant waste streams, and any other food items suitable for recycling, into a profitable, value-added product.

Depackaging Machines and Separation

The task for de-packaging machines and the associated separation equipment is to first of all to:

  • create a pure organic output of material the consistency of pulp, or a thick soup
  • a reject stream that is as clean and free from water content as possible.

The reject stream will contain varying amounts of packaging, but for the majority of food waste and mechanically separated organic content such as BMW (also known as OFMSW) a large proportion will be plastic in some form.

Avoiding the presence of moisture in the reject stream is important as moisture-laden content invariably contains calorific organic material which every biogas plant or compost facility operator will want to see in the pulp where it produces biogas – the source of profit for the plant operator.

Depackaging Machines separate the outside containers (wrappings) from the contents inside of the food box, packet, tin, drum, sacket etc., thereby making it possible to recover or recycle organic waste from the fate of being sent as waste to landfills. The issue of the need to avoid the waste of food has become increasingly common among businesses and councils globally.

Even source-separated food waste cannot go directly into the biogas production process/ biogas digester due to the amount of plastic present. Whether it be householders who discard the waste or catering facilities there is always plastic packaging present which would have a negative effect on digestion if allowed to remain.

All packaging containers must be opened before they go into a digester tank and the water content in both the pulp and the rejects (plastics and other material) outputs need to be low. All these requirements are critical to getting suitable food waste material into the digester tanks of an plant.

Types of Food Waste Depackaging Systems

There are many designs of food waste depackaging systems: some use a hammermill and others use a shredding machine. Others use paddles, and yet more have a squashing and squeezing action. The depackaging scene is rather like the early days of the motor car.

Each make of car was very different to start with. Motor cars gradually became more similar until today when technological evolution brought us to the point that each car has a combustion engine and the foot pedals, steering wheel, and clutch are universally the same. It will be the same for the repackaging industry one day, but for now, the systems used for it vary greatly.

A hammermill breaks and smashes everything into small pieces, using a lot of energy. The rotating hammers open the packaging of food waste and break apart all materials, leaving only the organic material available to be strained out. The only problem is that having broken everything so small there is a lot of microplastic which is the resulting mash. That’s the worst kind of plastic to sort and reprocess and the most damaging type of plastic to the environment and for wildlife in particular.

Food Waste Depackaging Machines

We think that an important property of depackaging machines is that they should not rely on the strategy seen in the early equipment. No longer should it be seen as acceptable to use size reduction as acceptable, due to the environmentally hazardous action of raising microplastic content which is likely, at least in part, to end up in the environment.

Food waste depackaging equipment should do the opposite of breaking things up small.  It should utilize multiple characteristics and less brutal forces to break open packages. Alternating tensile and compressive forces of the centrifuge and vortex action are two of the means that are used to break open the containers in the latest models of this equipment.

These forces can be used in combination to separate solid and liquid materials (for example restaurant waste). The process of using these different characteristics and switches in a food waste depackaging machine can also improve the efficiency of the subsequent AD plants and IVC (In-vessel Composting) operations.

Image text: "Food Waste Depackaging Systems".

Less Fragmented Packaging

The latest generation of purpose-designed multi-action food waste depackaging machines is designed to reduce the amount of fragmented packaging. The rotating paddles and flails help break up the packages. The flails and paddles carry the empty packages along the processing chamber’s upper side and the rejects can be ejected from the output point using water or air.

If you have a composting facility that handles similar wastes, these machines may be well worth the investment because they can cut contamination removal expenses while also creating new tipping fee opportunities for industrial food product depackaging and recycling.

In the best models more robust packaging, such as jars of peanut butter in plastic containers packed within a cardboard box, will be totally depackaged as the horizontal processing chamber progresses further down the length. In order to depackage food wastes, a turbo Separator does not require the addition of water in order to liquefy the food.

What is Energy Recovery from SSO?

It is the conversion of non-recyclable waste materials and packaging into usable energy such as heat, electricity, or fuel that is known as energy recovery from municipal waste. This can be accomplished through a variety of processes including combustion, gasification, pyrolysis, anaerobic digestion, and landfill gas recovery.

The Cleanaway Separator

The new food waste depackaging system developed by Cleanaway separates liquid and organic material ready for anaerobic digestion. The machines’ rotating cylinder at its heart uses paddles to open and move the packages along and out of the top of the chamber. If the packaging is durable, it will be depackaged by splitting and vibration in some machines helps to shed persistent stuck-on food.

This is a great option for processing large volumes of packaged food including restaurant waste. The depackaging machines have a wide range of capabilities and are compact and maintenance-free. The technology helps in the recovery of valuable organic materials.

The Cleanaway unit in Victoria processes ten tonnes of packaged food waste an hour. The unit is capable of recovering up to 99% of the material. Glass is not processed through the unit. The process takes place in a separate chamber, where a squeezing action causes the packaging to break. Once separated, the remaining materials are disposed of via anaerobic digestion. This method saves landfill space and reduces landfill carbon dioxide and methane emissions. If you have a depackaging unit, it will be the most efficient way to recycle your packaging.

Scott Equipment

Food waste depackaging machines manufactured by Scott Equipment use a horizontally configured chamber with rotating paddles and flails. These rotating blades break down the packaging at 400 rpm. The SSO Model is a horizontally configured machine that uses a hammer to break open the empty packages. These units are available in two different capacities. One unit has a 40-ton capacity while the other is a smaller one that can process source-separated organics and BMWat a lower flow rate.

The Dominator is another marque responsible for depackaging waste and separating plastic containers and plastic bottles from the contents of the containers and bottles.

Other Machines Used for Depackaging and Separation

Keeping food products out of landfills can be a difficult task, especially given the fact that many meals are packaged tightly, and some pots and punnets are very small.

A number of food waste depackaging machines combine a hammer and then a screw press to separate the pulp and the solids from packaged foods. In addition to using a hammer, a depackaging machine may use a combination of physical materials-characteristics to select and sort the incoming items. For example, a hammermill may be fed via a counter-rotating dual-auger mixing/feeding hopper and separate the liquid from the solid material (fibres) with a horizontal or vertical-pressure screw press.

It may use a single characteristic to break the package while using a different set of selectors to empty the packages.

Twister Depackager by Drycake

The Twister by Drycake also uses multiple characteristics to separate the recyclable organic fraction. While this may sound complicated, it’s essential for efficient recycling. The most flexible machines use several combinations of these variables to depackage all the different types of packaging used for food.

Separated packaging can then be shipped to a recycling facility or sold as RDF, resulting in even greater waste reduction while also providing the option for other revenue streams to be generated.

This equipment can depackage a wide range of wet and dry waste materials, including food, pharmaceutical, and municipal trash, as well as tetra packs, tin cans, and plastic bottles.

Tiger Machine

The Tiger machine is a leading food waste depackaging machine. It can be the front end of the AD process. There are many reference sites using the Tiger in the UK and is supported by its UK dealer, Blue Group. Parts for the Tiger machine are available same-day or next-day for immediate delivery.

There are no long intervals between the need for maintenance or repair for the machine, and it can be operated by a team of workers and training is available in any language.

Food Waste Depackaging Systems a Conclusion

Food waste depackaging equipment is used to separate the solid organic material from the packaging. The best equipment can also be used for BMW and OFMSW separation.

There is progress away from a strategy of reducing the particle size of the incoming food waste toward less destructive methods which aim to avoid microplastics being produced. Wherever possible the latest equipment strives to keep film bags and each packet almost whole and in one piece. While often items ejected aren’t whole, they are in multiple pieces instead of pulverised into indistinguishable shreds and flakes.

Modern equipment uses various types of selector properties and characteristics to separate the organic fraction. Without good depackaging and separation, the organic material cannot be removed. Without these machines, plastic packaging cannot be recycled, so food waste depackaging machines are vital for the plastic recycling industry. Not only useful for the AD process the new generation of these units also help IVC composting facilities accept packaged food.

With the latest technology, the process can be more streamlined, require less labour to supervise this equipment, and be more efficient. At the same time, the new equipment helps the environment. Check out the full list of food waste depackaging and separation equipment suppliers.

Farm Digesters and Anaerobic Digestion 101 Training

The formation of is a natural phenomenon that naturally occurs in wetland, manure stacks, and indeed in human and animal intestines. For centuries, humans have harvested the power of bacteriological digestion, by recovering naturally formed biogas to use for lighting, cooking, heating or to power mechanical engines. In the twentieth century, the process went out of favour while cheap fossil fuels were available. However, in the last 15 years, the process has seen a renaissance. In Asia, millions of family digesters are in use to provide cooking fuel and lighting in rural areas. During the second world war, German army trucks were fueled with biogas collected from farmers manure. Hence, the name “gas engines”.

‘Anaerobic’ Means Oxygen Deficient

The word ‘anaerobic’ means oxygen deficient. (AD) is the microbial degradation of organic material known as ‘feedstock’ (such as farm waste, food waste and energy crops) to produce biogas. This process is sometimes referred to as ‘bio methanation’. Typically, anaerobic digestion takes place in sealed, insulated tanks (digesters) in the absence of oxygen. It requires a heat source and is either a mesophilic process at temperatures of 35 to 40°c or a thermophilic process at 50 to 60°c.

On-farm Biogas Production

Farms and ranches are common places where anaerobic digestion can make sense. That’s because these are places where there are typically large quantities of organic material available. Well, run digesters effectively eliminate the environmental hazards of dairy farms and other animal feedlots. The environmental reasons typically motivate farmers to install an AD plant more often than the digester’s electrical or thermal energy generation potential does. Other potential common uses are in zoo waste management or any facility located near a continuous source of biomass such as a contained animal feeding operation.

We made a video of the most important part of this article. You can watch it below (we apologise as the sound quality is not perfect):

“Fixed Film” May Be the Future for Anaerobic Digesters

Scientists have for a long while been experimenting with a new method to improve the process in the future. It is possible that soon a “fixed film” digester may be available. In this type of system, a digester is filled with a medium such as rocks or plastic mesh. The medium acts as a resting and growing place for the bacteria. Many bacteria, instead of being flushed out with the effluent, would remain attached to the medium inside the digester. By retaining the bacteria within the fixed film digester, bacteria would be held inside the reactor to consume more organic matter per unit volume than in standard digesters.

Primary Objective of Some Recent US Research

Featured image text: "Farm digesters and anaerobic digestion 101".The primary objective of some recent research was to determine the technical requirements and economic feasibility of producing methane gas by anaerobic digestion of dairy-cow manure https://anaerobic-digestion.com/. A review of the literature revealed a substantial amount of laboratory experience with methane digestion using farm wastes, mainly dairy manure. However, information on experiences with full-scale digesters in operation on commercial-size farms in the United States was rare. As a consequence, it has been decided that the US government will provide funding to build a digester of sufficient size to study the engineering problems related to the use of digesters on dairy farms.

Capital Cost of an On-farm Anaerobic Digester

According to EPA Agstar, the capital cost of an on-farm anaerobic digester ranges from approximately $400,000 to $5,000,000 depending upon the size of the operation and technology used. The typical on-farm anaerobic digestion unit costs approximately $1. 2 million. Costs vary, depending upon the size of the unit, design, and features. The type of anaerobic digester necessary for your operation (and therefore the cost of the anaerobic digester) varies according to the number of livestock and technical considerations like temperature.

Who is Vanguard Renewables?

Vanguard Renewables develops, constructs, owns and operates farm powered anaerobic digestion (ad) facilities that provide a closed-loop organics (food and agricultural waste) to energy lifecycle solution. Their digesters sustain American farms, enable organic waste ban compliance, reduce climate-damaging greenhouse gas production and phosphorus, and produce renewable clean energy.

There has been quite a bit of discussion and information published about energy production from anaerobic digesters. The basic design concepts proven by successful digesters built in the 1980’s are applicable today. The additional benefits from anaerobic digestion have not been emphasized enough by the industry. Anaerobic digestion is more extensively used outside of the U.S. Where concern for the treatment of animal waste has been a concern for a longer time.

Agricultural Anaerobic Digesters: Design and Operation

With an average herd size of 113 mature cows, Cayuga county is home to 280 dairy farms and 31,500 dairy milking cows producing approximately 855 million gallons of milk per year. The Cayuga dairy industry is a major contributor to the county’s economy, employing nearly 1200 people while generating $140,000,000 of revenue from the sale of milk alone. At the same time, the Cayuga county dairy industry also produces.

Source: Jewell, William j. , ed. Energy, agriculture and waste management. Proceedings of the 1975 Cornell agricultural waste management conference. Ann Arbor: Ann Arbor science publishers, inc. , 1975. The mother earth news handbook of homemade power. New York: Bantam Books, inc. , 1974, pp. 278-355. Persson, s. P. E., and H. D. Bartlett. Agricultural anaerobic digesters: design and operation. University park, pa. : the Pennsylvania state university, college of agriculture, agricultural experiment station, bulletin 827, 1979.

Biogas Amounts and Composition

Biogas consists mostly of methane (ch4, around 65-70%) carbon dioxide (co2, around 25-30%) and varying quantities of water (h2o) and hydrogen sulphide (h2s) and some trace amounts of other compounds, which can be found, especially in waste dump biogas (e. G. Ammonia, nh3, hydrogen h2, nitrogen n2, and carbon monoxide, co). The amount of each gas in the mixture depends on many factors such as the type of digester and the kind of organic matter.

Use of the Digester Effluent

In a covered anaerobic lagoon design, methane is recovered and piped to the combustion device from a lagoon with a flexible cover. Some systems use a single cell for combined digestion and storage. Diagram of a covered anaerobic lagoon showing 2 cells, where the first cell collects the digester influent and traps the biogas and the second cell collects the digester effluent.

M. B. Kahn is currently completing the $22m upgrade on two of the five anaerobic digesters at the City of Columbia metropolitan wastewater treatment facility. Key modifications to the yard piping were completed to convey co-thickened primary and waste activated sludges from the existing trains one and two. Dissolved air flotation buildings to each anaerobic digester were constructed. Existing equipment, piping, valves, and appurtenances from existing digester head houses were demolished and replaced.

Small Home Digester Tip

For the small home digester, it’s good to paint any clear plastic walls in black so that the temperature keeps steady and for light not to go in, to not encourage the growth of algae. Algae produce oxygen which is not beneficial for anaerobic bacteria. We put a layer of gravel on the bottom of the tank in order to act as a growing place for bacteria (more surface area) and not to be flushed out with the effluent.

Before 2002, fewer than five dairies in California operated anaerobic manure digesters. Each dairy used the biogas produced by the digester to run an engine that powered a generator producing electricity for use at the dairy. There were no specific regulatory programs that applied to the digesters, although the regional water boards (RWBS) regulated wastes produced at the dairies, including effluent from the digesters.

Additional Benefits of Anaerobic Digesters

For future energy security and improvement in the use of natural resources, the depletion of conventional energy resources such as fossil fuel can be solved by the use of renewable energy sources. In the midst of numerous renewable energy sources and their production means is the sustainable generation of biogas through anaerobic digestion technology. Anaerobic digestion is a microbial process whereby organic carbon is converted by subsequent oxidation and reductions to its most oxidized state (CO2) and reduced form (CH4).

Biogas Plant Energy – A Badly Needed Alternative Sustainable Resource

the sustainable renewable resource production technology, is on a rising growth trend. The establishment from (AD) systems has actually sped up substantially in the past a number of years. And, one area of growth is for livestock manure stabilisation and also the associated energy manufacturing.

There are countless digesters running at industrial livestock centers in Europe, USA, Asia as well as elsewhere. which are generating clean energy and gas. Much of the jobs that generate electricity additionally catch waste heat for various in-house requirements.

The first anaerobic digestion (AD) center functioned in the mid-1800s in India. Yet, the technology came under disuse while there was plentiful low-cost oil.

It has seen a renaissance in a lot of current times. The country with the finest record of working with the modern technology is Denmark. That nation by 2000, had actually presented an energy production initiative that saw levels increase rapidly, and also they increased to that level in just a few years. Their lead has, within a few years, gone beyond by the high number in Germany, with close to 3,000 AD plants now running.

Now, various other nations have actually their own government plans developed and may now achieve comparable rapid increases in biogas manufacturing.

Energy from Renewable Sources Anaerobic Digestion is Growing

There are greater than 111 digesters running at industrial livestock centers in the United States which created around 215 million kWh equivalent of usable energy. Generating electricity (170 million kWh), biogas is utilized as boiler as well as residential fuel.

In 2015, for the first time the worth of energy generated in the UK by renewable resources was higher than that of energy generated by UK oil and also gas resources. Raised electricity produced from eco-friendly resources in between 2014 as well as 2015 (26%) contributed to the boost in worth in between this duration (UK National Stats).

Local Wastewater Therapy Achieves Surplus Anaerobic Digestion Energy Manufacturing

A biogas plant producing Biogas Energy also known as Anaerobic digestion energyDistricts, like the East Bay Municipal Energy Area in Northern California, recognized that in the course of treating wastewater from families, ranches as well as food handling facilities, they might add a step to produce a few of their very own energy.

the last 15 years have actually been a journey in search of greater efficiency and also energy manufacturing ability. Waste treatment is an energy intensive process, and with the setup of anaerobic digestion units as well as three wind turbines, generating more than one hundred percent of the energy needs of the WwTW can be attained, leaving extra power that can then be sold.

Biogas Production Not Intended From Making Use Of “Energy from Crops”

Practically any kind of biomass can be processed by AD consisting of food waste, energy plants, crop residues, slurry as well as manure. Cereals and also rape dish can be utilized as AD feedstocks, giving high biogas returns, yet are normally costly. Dedicated energy plants with high biomass such as maize, can be grown particularly for anaerobic digestion.

It is identified by many governments, including by EU policymakers, that utilizing food crops for energy manufacturing might cause food prices to rise. Policies have been established which prevent providing significant rewards to the use of food plants for energy in the last five or so years, use food plants is most likely to remain at a low degree worldwide, so increase in food prices as a result of biogas manufacturing is no longer likely to happen.

Anaerobic Digestion in Landfills Generates Biogas which Can Easily Retreat

Landfills are big contributors to carbon discharges as methane which is much more destructive as a greenhouse gas than the very same quantity of CO2. That indicates that it needs to constantly be accumulated and also shed in flares at the minimum. Much far better is to clean the land fill gas as well as use it to create electricity, or use it as a gas equivalent to all-natural gas (yet sustainable).

Several federal governments now call for landfill gas (biogas) to be gathered as well as flared, or used for its energy value. There are a number of conformity options, including flaring the gas or setting up a landfill gas use system.

Once the financial investment is made to make use of the energy, “land fill gas energy recuperation” offers communities as well as land fill proprietors the opportunity to reduce the expenses associated with governing compliance. They do it by transforming contaminating emissions into an important area source. It’s a real win-win situation.

Renewable Anaerobic Digestion Energy Creation

The inquiry is, which businesses are suitable for installing biogas to energy centers?

The key beneficiaries will certainly be tiny farms and smallholdings which create a great deal of organic waste.

A lot of small manufacturing facilities such as tanneries, fabric whitening and also passing away, dairy, slaughterhouses and so on, releasing to public sewers may likewise appropriate for biogas to energy tasks. However, lots of operator’s discover it’s hard to manage effluent treatment plants of their own as a result of economic climates of scale in pollution reduction.

Biogas to Energy Advantages

Transforming organic matter into methane in biogas to energy jobs has several benefits. Reusing/ recuperation/ re-use of products from the wastes of also small units by adopting appropriate technology is ending up being a sensible recommendation, particularly for the larger manufacturers.

That’s one area where generation of energy using biogas to energy procedures have actually verified to be economically eye-catching in several such cases.

The urban local waste (both fluid and also solid) such as industrial waste originating from milk producers, distilleries, tanneries, pulp and paper, and food handling sectors, etc., is being utilized to make energy through this process.

Plus, farming waste as well as biomass is made use of as AD plant feed in various types.

The anaerobic digestion procedure has an incredible capacity for energy generation if dealt with correctly.

Re-using Organic Waste With the Manufacturing of Renewable Resource

Areas throughout the world are handling their waste with less effect on watercourses, while reducing odour. They are beneficially re-using their organic waste with the manufacturing of renewable energy, plus boosting soils, with AD plant activator residue result sourced mulches as well as all-natural fertilizers.

Where are the Valuable Resources of Biogas Energy Material?

Farms as well as ranches are common areas where anaerobic digestion of waste products can make sense. There are usually big quantities of natural material available. This is valuable web content.

Digesters can effectively remove the environmental hazards of dairy farms and other animal supply raising businesses.

The ecological reasons to begin a biogas plant job, commonly encourage farmers more often than the digester’s electrical or thermal energy generation potential does.

Various other potential usual AD center usages are zoos or any type of center located near a constant resource of biomass such as a consisted of animal feeding operation.

Biogas Energy Solutions – An Example Biogas Study in Quebec

Laflamme Waste-to-Energy has suggested a biogas to energy option to two problems, those being waste monitoring as well as energy generation.

Adding an incorporated anaerobic waste treatment process to all sewage works, is an intriguing choice. Because of high financial investment expense and low energy worth in the district of Quebec, it is tough for a town to devote to that service.

A current clinical paper checked out the economic possibilities to manage natural material, organic portion of metropolitan strong waste, and metropolitan wastewater sludge by anaerobic digestion for a 150,000 inhabitant community.

Consideration additionally was provided to accomplishing significant energy generation as well as greenhouse gas exhaust reduction. It was located that making use of the biogas to co-generation remedy because task would certainly bring a reasonable repayment time on investment.

The enhancement of manure from bordering ranches would certainly be suggested and also if done well would be most likely to increase the biogas manufacturing by a third.

But, regulative controls enforced when AD plant feedstock importation takes places were found to raise the repayment time on financial investment unacceptably. That is, unless the leftover digestate can be utilized as a saleable asset, when it becomes a financially helpful natural fertiliser product, anaerobic digestion is not completely successful. Click here for more information.

When the financial advantages are evaluated as limited without regulatory help in some form to allow the sale of the output as a fertilizer, the regional regulator needs to be requested support.

As more biogas plants are built the scientific research will advance as well as the biogas energy benefits will remain to rise.

Recent Developments in Anaerobic Digestion in the UK, Europe and US

in the UK, Europe and US, is at a fascinating point in its development. It is possibly positioned on the edge of a massive development, however nobody can be certain.

Take a Look at the UK AD Industry

For 3 years the UK political scene has actually been consumed with disputing Brexit and also little else has been done. With a basic political election in December 2019, we thought we would blog about the news for anaerobic food digestion.

Gap Funding Urged to Support the Rollout of UK Biomethane Plants

Chancellor of the Exchequer Sajid Javid was been prompted just before the UK General Election was called, to provide stop gap financing to sustain the rollout of biomethane plants when the UK Renewable Heat Incentive system (RHI) expires in 2021.

In a letter sent to the Treasury, in advance of the scheduled date of next month’s Budget, the Anaerobic Digestion as well as Bioresources Association (ABDA) has required activity across government to extra effectively support the process, which traps the methane produced by natural waste.

It claims that it is ‘critical’ that there is a dedication of extra support for the anaerobic digestion (procedure past March 2021, when the RHI is due to end, including an active pot for financing for deploying biomethane plants.

The letter claims this support is essential while a future funding mechanism is developed since existing tools are not fully fit for objective. As an example, while the Contracts for Difference (CfDs) provide support for bigger AD plants, many in the industry are too small to be helped.

The UK Biogas Industry Needs Urgent UK Government Clarification of Financial Support if the UK is to Achieve Net Zero Emissions by 2050

Anaerobic digestion is currently acknowledged for its function in creating green power, however it also stops methane emissions from organic wastes left to damage down in landfill. There is currently a big untapped capacity for methane capture, usage and also conversion with countless tonnes of natural wastes from farming, food and also sewer presently not being treated with AD. In enhancement, AD treatment of organics recoups nutrients to fertilize diminished soils and also enhance their ability to sequester carbon.

The Treasury has been entrusted with coordinating federal government efforts to achieve Net Zero exhausts by 2050. Good cross-departmental plan coordination is for that reason important to enable the market to expand and achieve CO2 discharge reduction.

Government must clarify its economic assistance as an issue of necessity, especially as around 70 LAs will certainly be authorizing brand-new waste agreements in the time duration bring about the separate food waste collections application deadline.

The Government should sustain AD development to make it monetarily independent.

Anaerobic Digestion Screening System Proposed Using 3D Printed Mini-Bioreactors

Research job has demonstrated using small AD systems for high-throughput process testing to boost AD systems and has been successful. The excessive amount of biowaste as well as wastewater generated in our society needs to be dealt with correctly. Better carrying out of AD will contribute considerable to the lasting advantages of bio-waste as well as foul sewage (waste-water).

Understanding anaerobic digestion energy yeildToday, anaerobic digesters are used as systems for treating waste, with bioreactors typically offered in a range of various forms. The tools are not only utilized to deal with waste with the help of microorganisms, but they are liable for producing ‘high-value items’ like and also biofertilizers.

The authors explain that there is a demand for reactors on the micro- or mini-scale as anaerobic food digestion procedures end up being miniaturized. Throughout that procedure, sensory data can be increased, and yet maintained in a relatively small location, conserving cash as well as power.

AD in low functioning quantities is feasible and also reliable in regards to biogas amount as well as quality. The positive results achieved developed links between scale-down and also process security.

Worldwide Anaerobic Digestion Developments

Financial Investment Progress Made in North American Biogas Facilities

Organic waste is commonly either blazed and sent out as an ecological pollutant or left in a landfill where it decomposes and releases methane, a dangerous greenhouse gas that adds to environment modification. The use of anaerobic digester technology, provides an ecologically smart, proven technology to reduce damage by rendering down naturally degradable waste materials normally, using microorganisms.

Second, is a product called digestate, a natural ground-soil improver with the exact same organic and plant growth capacity as garden compost.

Is Anaerobic Digestion Beneficial and is Co-disposal Best

may be described as the equivalent of “composting without air”. Under normal conditions, such as in a compost bin, aerobic (oxygen breathing) organisms break down biodegradable organic materials into simpler forms of matter, producing carbon dioxide (CO2) in the process. But in anaerobic digestion, the biomass is decomposed with the exclusion of air. In the absence of oxygen, certain microorganisms break down the biomass to produce which is in general 40% to 60% methane (CH4), a clean-burning renewable combustible gas.

Is Anaerobic Digestion Truly Beneficial to the Environment?

Image shows a car powered by biogas from the anaerobic digestion process.
A car powered by biogas from the anaerobic digestion process. CC BY-NC-ND by DECCgovuk

We all want what is best for the environment. Therefore, we will support any initiative where the variables have been considered and the waste is dealt with in a way which maximizes the recovered value while minimizing the environmental impact. We believe the combined energy recovery and recycling achievable through anaerobic digestion often make it the best recovery option for certain bio-wastes, such as agricultural manure and slurry and separately-collected food waste. There is also some uncertainty over the relative value of carbon, when used as a source of energy, compared with its long-term value in augmenting soil organic matter.  Recent research has placed a high value of the fibrous output (digestate from the Anaerobic Digestion Process) as a soil organic matter for carbon storage.

While all Anaerobic Digestion facilities should also make use of the waste heat in CHP schemes, and provided that they do. It is generally recognized that anaerobic digestion plants hold a strong record for environmental benefit. This is for renewable energy production, reduction in agricultural pollution, and raising the carbon content of the land when the fibrous digestate is used as a soil improver/ fertilizer.

In the Temperate Parts of the Globe AD Plants Require Heating?

In all but the hottest climates AD plants generally require heating to maintain their chosen operating temperature ranges.

An image of a typical looking agricultural anaerobic digestion plant.
A typical looking agricultural anaerobic digestion plant.

To have to heat large tanks of initially cold feedstock which for all the most common “Wet” biogas process designs, is a heavy burden on the net energy output of any Anaerobic Digestion Process plant. Generally, the choice of a temperature range for anaerobic digestion is strictly dependent on the bio-climatic conditions.

In tropical countries, like Tunisia, where the ambient temperature is higher than 25 degC for a period of more than 8 months in a year, thermophilic anaerobic digestion is readily applied and may be self sustaining without heating.

But, in much cooler Sweden, for example the heating demand is high. So, most plants are “mesophilic” in their operating temperature range, this being cooler than “thermophilic” temperature range digesters. Furthermore, research is currently underway for possible anaerobic digestion under low temperature conditions.

In the USA, anaerobic digestion of sludge under thermophilic conditions has been found problematic in cold states. However, it is well established in Europe where highly efficient well heat-insulated modern Anaerobic Digestion plants are being built, especially for the treatment of the organic fraction of municipal solid waste (Ahring et al., 2002).

What is Co-digestion Mean when Applied to Anaerobic Digestion Processed?

Co-digestion simply means that more than one biomass source is used to feed the biogas plant. Co-digestion can raise the yield of biogas per unit of carbon source in the feedstock, because it usually helps to improve the C:N (Carbon to Nitrogen Ratio) of the feedstock. The secret of a healthy bio-reactor lies in a good C:N ratio. Green wastes/ materials have a high nitrogen ratio, whereas brown/ woody materials have a low C:N ratio.

Co-digestion provides the opportunity for the green and brown(woody) wastes to be stockpiled and mixed in quantities that when fed into the bio-reactor provide a good C:N balance.

In a report from WERF (2014a), co-digestion was analyzed with six substrates: canola oil, restaurant grease, ethanol silage, cheese whey, chicken manure and bio-diesel glycerin.  The different feedstock have been tested and compared to the thickened sludge only case study: in all the scenarios presented, biogas production was increased with respect to the anaerobic digestion of sludge only.

Better results are related to glycerin, grease and cheese whey, while chicken manure has a very reduced influence on the overall biogas production (because of the lower specific COD content respect to the other feedstocks). Glycerin and restaurant grease show, in the laboratory phase, an increase in biogas production from 35% (in the first 25 days) to 99% (in the second 25 days).

Source separated organics (SSO) [food scraps and yard waste] were a few year ago thought to be best aerobically composted, but recent research has shown anaerobic digestion makes the best sense, especially in urban areas where land for aerobic composting is not available.

Digested food waste is also high in nitrogen, so it makes a good companion when combined with say an agricultural dairy farm biogas plant which is also fed with farm manure.

Nevertheless, the fibrous output (digestate) still needs to be aerobically composted after digestion to condition it. Food scraps and yard waste can be mixed with sewage sludge (“biosolids”), as long as the biosolids are from regulated sewage works such as in Europe, and where contaminant loadings do not preclude the land application of the digestate output.

It would not make sense to mix toxic sewage sludge with yard waste (e.g. as unless the digestate can be placed on the land as fertilizer it’s disposal comes at a high cost. The yard waste from a dairy can be much cleaner, and shouldn’t be blended with more toxic sludges. Doing so also makes it ineligible for accreditation as a suitable fertilizer, as is also the case for compost under organic certification standards, which bars heavy-metal rich sewage sludge as fertilizer.

How to Improve the Gas Yielded from Anaerobic Digestion Feed Materials

As we have indicated earlier in this article, the methane output is actually one of several great benefits from the process. Anaerobic digestion also reduces waste and odor.

An anaerobic digestion plant.
View of an anaerobic digestion plant. CC BY-SA by Peter O’Connor aka anemoneprojectors

The biogas yield is actually dependent on the rate of Cellulose solubilization. Cellulose solubilization is the rate determining step in the anaerobic digestion of organic solid waste.

An increase in the rate of solubilization should lead to an increase in the overall efficiency of the anaerobic digestion process. Processes are being developed to raise the rate of cell-rupture in “hard-to-digest” feedstocks, and the most readily abundant of such sources is sewage sludge.

For sewage sludge there are now several processes which speed up biogas production, and some of these are:

  • hydrolysis (heating at high-pressure above the normal boiling point
  • use of enzymes to break down cell-walls
  • physical methods to create lysis, such as Utrasound, and “exploding” (i.e. repeated rapid pressure changes).

Reactor studies on cellulose solubilization rates are typically conducted in anaerobic, mesophilic environments with approximately neutral pH and may be inoculated from a range of source environments including landfill leachate, manure, sewage sludge, anaerobic digesters, or the rumen.

Are All Anaerobic Digestion Process and Biogas Plants Home to the Same Micro-organisms?

Despite similarities in the operating conditions of reactors inoculated from different source environments, the respective microbial communities may differ in many respects, including their species profile, biofilm architecture, nutritional requirements, particle colonization, and hydrolysis rates. Microbial communities in cellulolytic environments are highly complex with interactions among numerous trophic groups required to carry out the digestion process.


It is possible to view Anaerobic digestion as the equivalent of “composting without air”.

Anaerobic digestion isn’t simply “greenwash” it does provide substantial green benefits, and the waste heat should be used in CHP systems, in all biogas projects.

Biogas production for co-digestion is greater than for separate digestion of the same materials.

Anaerobic Digestion Pros and Cons

is a great process for creating renewable energy, and it is also unique in that it solves many other problems, especially if the feedstock material which is used as the substrate to “fuel” the anaerobic digestion is a waste material, and not a food crop.

So, to avoid this article becoming excessively long I am limiting this article to a discussion of and cons, for anaerobic digestion (AD) plants where the feedstock is 100% waste material and to commercial anaerobic digestion plants built in the industrialized nations. AD plants, which are more often called “ plants” in the industrializing nations, have a slightly different list of advantages and disadvantages. That’s because by their nature they are much smaller, and usually built for different reasons from biogas in Europe, or the US, for example.

 Anaerobic Digestion Pros

1. Produce renewable energy with the smallest possible impact in terms of carbon dioxide emissions.

2. Can be used to process diseased and infected organic matter, and as long as a suitably high temperature is attained during the process, a safe pasteurized output is produced which will not spread disease.

3. When waste feedstock materials like food waste are digested,which would otherwise have been sent to a landfill, the volume of waste which goes to landfill is reduced.

4. Diversion of organic waste away from landfill, will also have the effect of reducing the amount of organic “rottable” (putrescible) matter in landfills, making them less likely to cause pollution in the future.

5. The output, known as digestate, can be used as a crop fertilizer which also has the ability to make many plants more disease resistant. When used in arid climates it can improve the water retaining ability of the soil, and reduce irrigation requirements.

6. The liquid digestate is a better fertilizer in many ways than normal chemical fertilizers.

7. The fibrous digestate the fibrous digestate has many uses. If it is not spread immediately on fields it may be used in some circumstances as a leading for livestock.

8. The digestate produces less odour when it is spread on farmland, and is less likely cause pollution of local rivers and streams and spreading untreated manure.

9. When the biogas is used on-site to generate electricity there is spare heat in the form of the engine cooling water, which can be used on the site it is created (e.g. on the farm for heating, or to heat the factory where the biogas plant is installed, or a near neighbour. That is known as CHP (Combined Heat and Power).

10. Certain businesses that pay a carbon levy for their carbon dioxide emissions can offset their levy costs against the carbon savings from running their own biogas plant.

 Anaerobic Digestion Cons

1. Commercial anaerobic digestion plants are costly to build and usually need bank loans to finance them.

2. The plants need expert people to design, construct build, and operate them. They must be attended pretty much every day, to ensure they run correctly, and are more complex than say installing a solar cell.

3. To be successful each anaerobic digestion plant must have a reliable source, and usually a number of different reliable sources, of feedstock materials. That can be diffilcult to obtain.

4. Suitable sites can be difficult to find as the public may object to planning applications for AD plants.


These are the main advantages and disadvantages of anaerobic digestion. We hope that this article has helped you understand that there are many more advantages to using the anaerobic digestion process than disadvantages.

Recent UK Anaerobic Digestion Developments and Future Projections

The growth of in the UK has not met Defra’s strategy target of 2011, when 1,000 new digesters were to be built by 2015. In fact less than half that figure was achieved, nevertheless the industry has been growing rapidly in real terms in the UK. Considering, the difficult economic circumstances, and reticence until quite recently on behalf of potential investors, the number of plants which have been brought on-stream is remarkable.


In the area of Waste Management, the the charity of plants will be needed to process food waste and in particular food waste collected from households. One benefit of slower adoption of anaerobic digestion technology, has been the additional time that has enabled plant process technology to be developed.


It is worth remembering that during the 1980s a host of innovative but unfortunately largely unsuccessful process technologies were heralded as the ideal treatment method for the UK’s industrial organic wastes. A number of new processes were introduced such as:


a) The Upflow Anaerobic Sludge Blanket (UASB)

b) Expanded Granular Sludge Blanket (EGSB)

c) Anaerobic filter.


While such processes were undoubtedly successful for certain quite closely site-specific organic wastes, they were over-sold, and after a rapid initial take-up were then found unable to live up to expectations, and were soon abandoned. Inevitably, this left many clients with heavy costs replacing failing equipment.


A number of commentators have suggested that these experiences left a legacy of distrust in the AD process as a whole which has persisted until quite recently. In the UK this may have led, at least in part, to what was almost a complete absence of industrial anaerobic digestion plants, in the last decade of the century.


When anaerobic digestion plants did start to emerge it was the simplest of single reactor (mesophilic) type of AD plants, which lone UK advocates of anaerobic digestion had continued to espouse. The most successful of these was the plants produced by Michael Chesshire, and his company Farmgas. He was able to show that those processes used in his on-farm biogas plant systems were capable of reliable long-term profitability when the UK DoE (now Defra) chose to award his successor company to Farmgas, named Biogen the funds to demonstrate it on a feed stock of food waste.


At the same time, during the latter part of the 2010s, work by Southampton University researchers showed that problems reported with food waste only biogas plant operation after more than a year from commissioning were avoidable. Process problems would in future simply be avoided by adding certain depleted (and essential) rare earth’s to the feed materials.


The reason that Anaerobic Digestion has been, and still is viewed by UK government department, Defra, as an ideal process which they will subsidise, is because it holds the key to their delivery of a number of government targets, as follows:


– greenhouse gas emisions reduction

– targets for renewable energy generation

– targets for reduction of waste tonnages sent to landfill as required by the EU Landfill Directive

– targets for recycling.


Paradoxically, due to the fact that large quantities of water are added to the standard AD process, this method of waste “treatment” results in a much larger volume of material after the process than before it. It is only made viable to pay what it costs to dispose of the resulting “digestate” volumes, by the high value of the energy produced.


Dry type ananerobic digestion systems which produce less liquid digestate, are being built but don’t achieve as high a biogas yield as the stadard “wet” process. So, while selling the gas remains as the main income, uptake will be likely to remain muted.


Future Projections


The future for the next 5 years of anaerobic digestion industry development will be increasing numbers of biogas plants using essentially the existing core process plant design, in which the vast majority of plants will be single tank mesophilic reactors. It is expected that in accordance with EU requirements, which are likely to be passed requiring all councils to collect and digest household food waste, and government zero-waste pledges, the main demand within the waste management sector will be for food waste digesters.


Source: http://eprints.whiterose.ac.uk/42993/7/horanNJ2.pdf

On-Farm Anaerobic Digestion Plants

On-farm or what are also known as farm-scale plants are most often built to provide an income from the that is made from manure. The manure which is treated may be from stock litter waste created when stock is kept under cover, plus farm slurries and farmyard run off. There may be other sources of organic feedstock added to these plants, as the most cases they are primarily intended to take manure.

Due to economic constraints, and the need to avoid time spent running these units and maintaining them, these anaerobic digestion systems are invariably the simplest of designs and built to the lowest budget’s possible. In fact, in many cases these plants are, what is known as a “distress purchase”, because the main motivation towards the installation, may be a need to reduce farm run-off pollution from the working areas of farm buildings, and also in highly nitrate sensitive watercourse areas, pollution of nearby watercourses. Another reason for installing these plants can also be for odour reduction.

Many of these plants are appearing in the landscape, throughout much of Europe and the U.S. They are single stage, continuously stirred tank reactors (CSTRs). In other words they comprise of essentially just one large mixed digester vessel. The mixture of the feedstock, which is made into a slurry by cominution and the addition of recirculated digestate, or in the case of existing slurry just a slurry itself, is pumped into the large reactor tank. The mixed liquid, which is known as the substrate in these plants has a solids concentration of approximately 4% to 5%, and the temperature is normally 35 C. It is known as mesophilic digestion.

The financial viability of these plants is often finely balanced. That being the case, that being the case there have been a number of cases where budgets have been paired and the resulting newly installed biogas installations have been almost too cheap for viable operation. Cheap tank construction, and rushed installation, with the aim of keeping costs down, and minimizing construction periods so that plant owner can commission the facility rapidly and begin to get pay back very quickly, can play so much pressure on installation contractors, are too many corners are cut. Such plants, seldom meet expectations, and the design life of them can by experience, the remarkably short. It is unfortunate, that in current times, when there are many anaerobic digestion EPC contractors vying for work, that each is being forced to compete on price. That means that we can expect a surprisingly large rate of plant failures in the next few years, for the owners of budget on-farm biogas digesters.

Many biogas plants of this type currently being put forward in bids by the owners of on-farm biogas plants, to accept additional household food waste. While this may be a salvation for the farming business, as accepting say to up to 10 per cent of its throughput as food waste, will greatly increase the biogas yield, low cost budget biogas plants seldom possess sufficiently sophisticated pipework and pumping equipment, for this use.

The result, seen in many such food waste co-generation contracts, has been that adding the food waste has resulted in plant blockages, lost biogas production due to excessive downtime, and unhappy council waste disposal departments. The owners of on-farm biogas digesters need to take professional advice from expert biogas plant designers before they bid, and include in their prices for upgrading their biogas plant systems, before they start to add food waste.

Them we all should applaud farming businesses that are taking on board a real financial risk in installing farm biogas plants. Not only are they are improving the environment of their farms for the good of the general public, but they are providing much needed renewable energy, without which governments would be unable to reduce the rate of global warming caused by greenhouse gases emitted by fossil fuel consumption.

Understanding Net Energy Yields of Anaerobic Digestion Plants

Understanding anaerobic digestion energy yeild
By Francis Flinch (Own work) [CC BY 3.0],
via Wikimedia Commons
 The net energy yield of , which is the sale-able energy left after all the sacrificial energy demands of running an plant are taken into account, is a subject of huge concern for all AD plant operators. Not only is the sale of the net energy the main income for most such plants, but a plant’s claim to legitimacy as a low-carbon energy producer is also at stake.

Strictly, also the plant operator should be able to quantify the energy used in the construction and maintenance of his plant and carbon dioxide emissions caused, as that will have a bearing on not only lifetime biogas plant costs, but also be part of the whole-life plant energy (and carbon footprint) balance. Ultimately, it is this essential to understand how environmentally sustainable any anaerobic digestion plant truly is.

The net energy yield from anaerobic digestion is calculated from the methane output achieved under operational conditions, less the energy losses incurred during feedstock transport and handling, before the digestion process starts.

In addition, digester heating and mixing, and the energy costs of digestate handling and disposal need to be factored-in. Anaerobic digestion typically yields methane in quantities ranging from 0.2 Nm3 methane/ kg VSrem for low calorific value feedstocks, for example farmyard manures/ slurries, to more than 0.5Nm3 methane/kg VSrem for high strength feedstocks (e.g. food waste).

The key to optimising this yield is to optimise the volatile solids VS removal. In other words, to make sure that as much as possible of the organic content within the feed material is digested, and does not simply avoid being further decomposed in its passage through the process, and flow out in the digestate. Achieving optimisation requires that close attention is paid to operation and maintenance 24/7, and a healthy micro-organism population in the digester.

The internal costs of feedstock processing and digestion typically account for 15 to 20 percent of the energy yield. This cost is relatively consistent and unchanging for the life of any particular plant, as long as the feedstock type and digestate disposal routes remain unchanged.

The same cannot be said for the energy used for all activities in feedstock delivery and digest recycling, because this is solely dependent on the transportation distances travelled.

To illustrate this point, consider the degree of change should the source of the feedstock alters, or a digestate disposal route ceases to exist. In such circumstances, the net available energy may fall-off to unsustainable levels.

To avoid this biogas plant operators must see it as of the highest priority to negotiate secure sources of feedstock, and fall-back recycling routes for the digestate. Without this, anaerobic digestion plant owners/ operators might find themselves, at some future date, unable to prevent their biogas project descending into an energy deficit.

It is clear that an energy deficit at a biogas plant, if it was to occur, would render the project concerned unsustainable, and that coupled with a likely loss of business goodwill, is a result which it is all-important to guard against.

This in implies that biogas plant operators, who wish to safeguard their investment, must sign-up the producers of the organic waste they use as their feed material in-advance. The need is for long-term contracts, set up with terms compiled from professional advice, for stated quantities and costs of feedstock set-in advance, and the with the assured availability of farmland suitable for recycling the digestate.

Centralised Anaerobic Digestion Plants

Centralised anaerobic digestion plants, are a great idea, because they allow the pooling of resources to achieve multiple aims. These include not just for the plant operator to make a profit from a successful energy (biogas production) business, but also to sanitise waste for the health of a community, but also reduce water pollution, control odours, and more. The concept originated in Denmark, where they possibly still have highest number of plants.

This type of biogas plant is referred to a CAD plant.

CAD plants characterised for design purposes as very flexible plants capable of processing a wide variety of feed stocks. However, they are invariably at their core a manure treatment plant based design, and agricultural.

In the most common application of CAD, several farms co-operate to treat their phone animal wastes in the single facility. It is not uncommon for local industrial and municipal wastes, also to be accepted and as a rule of thumb these may be taken as feed materials providing no more than 10 per cent of the total input material. This 10 percent can be viewed as an additional revenue because a gate fee will be charged. As long as the imported materials remain below 10%, any contamination will be unlikely to affect significantly the quality of the output as digestate, in reality.

However, unfortunately this commonsense approach to allowing the output to be used as fertilizer by the farms within a co-operative, may be impeded by difficult to comprehend and apparently unnecessary rules applicable in many European countries at the current time. Notwithstanding this difficulty, which will hopefully be resolved in the not too distant future, by a reclassification of many so-called waste materials.

Given, that as we said earlier, CAD plants are at their core based around agricultural waste treatment, it is not surprising that characteristically they are almost all based upon tried and tested manure digestion technology. By this, it means that they are low solids, mesophilic temperature range, type plants. They are designed around the water contents of a typical slurry from farms. This technology also happens to be very similar to the sewage sludge treatment biogas plant design. These designs are some of the earliest and most thoroughly proven which are available within the AD industry. Many contractors offer these types of plants, so this market is highly competitive and good value should be achievable from the best contractors who are active in supplying this type of biogas plant.

Four CAD plants to be run successfully, really proactive management is necessary to ensure that the right next of different feedstocks are continually being delivered to the plant, not only by the other members of the co-operative, but also by those organisations also contributing organic MSW, and industrial or commercial organic waste. Providing that this balancing act, is achievable given seasonal fluctuations, the nature of holidays in tourist areas, and the need for continuation of feedstock supply in times when there may be growing competition for feedstocks, this is a good business plan.

The biogas generation rates from CAD facilities in reality varies as much as the feedstock does. Estimates are hard to come by, but the publication titled; “Biological techniques in solid Waste management and land remediation”, published by the Chartered Institution of Wastes Management, 2009, CIWM Business Services Limited, Northampton, UK, WWW.CIWM.CO.UK, suggests typical rates.

Using data from Denmark an average generation rate of 37 m3/m3 has been calculated. That sounds quite definitive, but in reality spread of biogas yields is large and varies from 23 to 90 cubic metres of biogas per cubic metre of feedstock. If these plants are operating on manure alone it is suggested that the yield in biogas would be something like 20 cubic metres of biogas cubic metre of feedstock. From that it can be assumed that the highest yields will be those from the CAD plants which are excepting highly calorific feedstocks in the form of the wastes such as household food waste.

In the examples used here, and based on experience from Denmark, the viability of these plants is heavily dependent upon them using their own farm and as the output destination for their digestate. These plants would not generally be economically viable if they were not able to use their own co-operative’s digestate and fertiliser, and instead had the cost of digestate treatment to finance.

Of course, this should not be allowed to detract from the fact that they produce biogas which is every bit as good as that produced by other types of processes other than anaerobic digestion plants. It can be used for heating the farms, schools and other facilities in the locality. It can raise steam for food processing/ bottling plants, generate electricity for off-grid locations, and provide vehicle fuel for farm vehicles and local transport.

Very few people would not agree that there is a bright future for and energy costs rise, as they surely will.

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Biogas – What it is and How it is Used

Biogas is the gas produced by the of organic materials. It takes place in what is known as a digester. These are becoming increasingly common sights in the countryside. They are easily recognized once you have seen one or two. The main fermentation tanks where the anaerobic digestion takes place is usually circular in plan, green in colour (to make them inconspicuous), and at least 5 to 6 metres high around the perimeter. In diameter they may be from 15 metres to 35 metres, and over the top of them is placed a circular plastic membrane in which the biogas collects.

Chemically, biogas comprises a mixture of methane at 55-65%, and carbon dioxide at 35-45%, the remainder being small quantities of other gases including hydrogen sulphide (H2S) and ammonia (NH4). The biogas contains water vapour at saturation point as well. Most biogas plant tanks and pipework systems are made of steel. Steel is easily corroded by H2S in water, as this is a strong acid even a small quantity of H2S can cause bad corrosion. The secret of successful biogas production without costly downtime, is avoiding corrosion. Achieving this is dependent upon the operator keeping the hydrogen sulphide present, as low as possible to prevent corrosion. Many biogas plant design and build contractors have their own methods for minimizing this corrosion, and sponge filters made of iron, and carefully controlled air-injection, are just two of the methods used. One or two biogas plant contractors avoid concerns about corrosion by using non-corrodable stainless steel as the material of construction. This can be a wise move, but does cost more money during construction of the biogas plant.

Biogas – How It is Used

There is a straightforward use for the biogas. It can be burnt. It has a high calorific (heat) value, it burns cleanly, and is just the same as many other gases. At its simplest, all that is needed is a simple stove gas-burning ring. If there is a factory or any other user of heat, they may just burn the gas to heat a workspace. However, it is best when considering the efficient use of the energy at this level, to use it to run a gas engine which will convert the energy into electricity, and also heat. That heat, is nothing other than the heat which is taken out from the cooling jacket of the engine to keep it cool. It is normally hot enough to run through pipework and to supply radiators to heat the space in homes and factories. When this is done it is known as combined heat and power (CHP). As the cost of energy rises and society seeks to reduce the harmful emission of carbon into the earth’s atmosphere, more and more CHP installations at biogas plants are being built.

However, the cost of by piping this heat, with all the insulation needed, is high. To keep construction costs viably low, the users of the heat provided in CHP schemes need to be close to be anaerobic digestion plant. An example of a very good CHP scheme can be when a landfill is constructed in the void left by the extraction of clay for brick production. If brick production continues at the site, the electricity, and the waste heat (CHP) can be used to heat up the bricks and save a lot of fossil fuel consumption, while also reducing the cost of brick production.

Of course, if the biogas is used to generate electricity and there is no user for electricity nearby, it will be necessary to connect it to the local electricity grid. At some locations this connection may not be possible within a reasonable distance, and/ or the costs charged by the electricity company may not be affordable. When that happens the biogas can be used as vehicle fuel.

This can be done at several different levels. At its cheapest, the biogas may just be given a minimum of clean-up and used in cars and plant operated by the biogas plant owner. In such a case it may make economic sense to keep the clean-up to a minimum and accepts that using it will simply be at the cost of additional corrosion maintenance in those engines. After-all, the energy will be very cheap and usually taxed at a very low rate.

At the next level of sophistication, the most sophisticated proprietary biogas upgrading equipment may be installed to produce a refined (upgraded) biogas which is to all intents and purposes, equivalent to compressed natural gas (CNG). However, at this intermediate level of upgrading quality the CNG would not pass the rigorous tests applied for its commercial and retail sale as, CNG quality gas. Nevertheless, the use of this gas may be entirely intended for the biogas plants owner’s sole use, to fuel his local fleet. In such cases, there is no need for formal certification of this gas quality. Such biogas upgrading projects are becoming very popular, and indeed these are the sorts of installations which supply the biogas to many of the much publicized “green” buses and “green” trucks seen on our highways nowadays.

The highest level of biogas upgrading, which requires not only the highest quality upgrading, but also additional monitoring and certifying of the biogas quality, is the production of grid quality compressed natural gas (CNG). This gas is so pure and guaranteed to be consistently pure, that it is to all intents and purposes the same as natural gas when it is taken that out of gas wells.

This gas is very valuable, commands the highest price, and as long as there is a high pressure gas-main nearby, can be injected into the local natural gas supply. The proponents of sustainable living, point out that this use of biogas is the most sustainable and highly efficient way to use renewable biogas. That is because when electricity is generated there is a large power-loss in the cables and overhead lines, amounting to about 30 per cent in many cases before it reaches houses and factories where it is used. This is unavoidable and is inherent in all electricity generation and distribution systems.

The choice of the best biogas use is made for each site by considering first of all the other there is a local user for the energy (for example in a factory), second what it would cost to connect the biogas plant to the electricity network, and thirdly whether there is an opportunity to connect to a pressure gas pipeline. If none of those are suitable, it is always possible to simply use the biogas to power transport vehicles.

Biogas Safety Considerations

Finally, no article about what biogas is, and how it is used, is complete without pointing out that biogas (methane) is an explosive gas and at all times during process design, commissioning, operation and maintenance, great care must be taken to avoid accidents. All biogas plants, must be fitted with appropriate safety equipment. In Europe it is a matter of complying with a number of statutory regulations and guidance documents. The main regulations stem from the ATEX regulations and are based in each EU country upon the EU ATEX directives. Typical equipment includes gas-flares to burn-off gas during emergencies, flame arrestors, automatic emergency cut off valves, carbon monoxide detectors, and special AREX certified electrical and electronic equipment designed so that it does not create any sparks or have any hot components.

In addition to all the necessary equipment needed to provide for safe operation of these plants when explosive gas is present, the operator of every biogas plant will also need to take care of the human factor. During certain maintenance activities, and in certain areas of the biogas plant, staff must always take precautions that their actions do not create the risk of an explosion. Clearly, such actions of smoking are outlawed, but also actions which may cause a spark, such as casual use of a hammer causing a spark, must be guarded against. For this reason there are guidelines and good practise manuals that must be used at all times when present in the vicinity of biogas plant equipment. Explosions are rare, but unfortunately the consequences are very serious when one does occur. That means that all biogas plant operative staff must be trained to work safely, and extreme caution is essential wherever working upon biogas plant maintenance.

Anaerobic Digestion of Wastewater Treatment Sludge


of the sludge which is generated in huge quantities during the treatment of sewage is now the for treating and disposing of wastewater treatment sludge. This is a major change which has occurred over the last 15 years. Prior to that, when the energy costs were low, was incineration. However, incineration is now recognized as being not only too expensive, due to current high costs of energy, but also to damaging, due to the very high carbon dioxide emissions incineration incurs.

Looking back in time, when modern sewage treatment began in the UK, the major cities all loaded their into barges or specially equipped seagoing vessels and simply dumped the sludge out at sea. That was the lowest cost option and still would be if international marine treaties had not banned the marine discharge of sewage sludge. The the next step in sewage sludge disposal, adopted by the majority of the sewage undertakers was to spread the on land, as a fertilizer.

However, due to the presence of heavy metals in domestic sewage which remained within the sludge, and tended to stay in the soil and build-up toward levels that would eventually mean that crops grown with themselves contain these metals at concentrations that would make them dangerous to eat.

Although, the spreading of sewage sludge on land is still practiced in rural areas, where metals content in sewage is anyway much lower than in industrial areas, it soon became apparent that an alternative was necessary. That alternative was incineration, but as anyone who thinks deeply about this will realize, incineration makes very little sense when the alternative of anaerobic digestion is considered.

To put it simply, in AD process takes sewage sludge (a form energy), and releases that energy for productive use, whereas incineration takes this form of energy and burns yet more energy, just to destroy it and send it up a chimney where it becomes just one more carbon emission increasing climate change even more.

In comparison with other locations of the AD process, digestion and of sewage sludge is greatly simplified due to the fact that sludge is produced by the same organisation and by a known treatment process (i.e. the main sewage works treatment facility). That means that it is much easier to control the quality of the feed sludge, and is the case for a general AD plant taking waste under contract from a variety of sources.

However, what does make sewage sludge digestion more difficult, is the fact that more directly reactive organic matter will have been removed during the anaerobic sewage treatment stage, through which the sludge settles out. Unlike anaerobic digestion the organic fraction of municipal solid waste, and wastes like household food waste, which release in their organic content comparatively easily, sewage sludge needs pre-treatment before it can be successfully digested for a good gas yield per cubic metre.

For that reason, all sewage sludge AD plants have an added stage before the sludge enters the digester tank. The purpose of that stage is to break down the particles so that they release their energy. The most popular pre-treatment stage is known as hydrolysis. Hydrolysis simply means heating for sludge to a temperature above normal boiling point, under high pressure, and maintaining that temperature and pressure for a set period of time.

There are alternatives to using hydrolysis to do this, microwave ultrasound has been used, and the addition of chemicals can have the same result. However, there is a plant is already producing its own heat and power and seems to be little reason for not using some of that heat and power in the hydrolysis process. In fact the hydrolysis process, we will implemented, should release much more energy from the sludge than the sacrificial energy required to run it.

This must not forget that the primary reason for carrying out anaerobic digestion on sewage sludge is also to treat the sludge so that it can be disposed of in a sanitary and loan pollution manner. Thankfully, the digestate from sewage sludge anaerobic digestion plants meets that requirement very well.

There is still of course a need to ensure that heavy metals are not discharge to land when the digestate is used as a soil improver and a fertilizer. Better control of industrial discharges has greatly reduced the metals content of sewage sludge, and in all but the most heavily industrialized areas of problem may no longer exist. However, much of the metal content may be found in the fibrous digestate and if so, after a period of composting in the open air coupled with dry, this material may be incinerated or incorporated into such products has building insulation board, or other non food related uses.

Anaerobic Digestion Systems for Biowaste


For the purpose of this article, we define has any one of the following waste types, or combination of these waste types:

1. Source segregated household biodegradable waste that is, the food wastes from kitchens and green waste from domestic gardens.

2. The organic fraction of mixed Municipal Solid Waste (MSW).

3. Agricultural waste.

4. Sewage sludge.

5. Industrial organic waste.

How Biowaste is Digested in AD Systems

First the Biowaste is comminuted (crushed and chopped up). This reduces the size of each particle and increases the surface area overall for optimum digestion.

If there are contaminants present, these are dealt with. Metals, plastics and glass are removed at this point by systems which may be manual (e.g. conveyor picking), or automatic.

The incoming waste material is mixed with previously digested material, and liquids, to inoculate the new material with digester microorganisms. This is a vital stage and mixing must be thorough for optimum performance. The mixture now contains sufficient water to be pumped. If necessary additional fresh water may be added at this stage.

This mixture is delivered into the digestion vessel, known as the digester or reactor. In many cases, there may be too digesters. Within the digester the organisms undergo fermentation in which degradation of complex molecules takes place and production occurs.

During the digestion, these decomposition that takes place creates water from the more complex molecules, so the resulting digestate will have a higher proportion of water in it and did originally. Although, biogas, which is mostly methane is given of, the water escapes during the digestion stage.

Digestate will then be discharged, usually as a constant flow, and dewatered. In many plants, this may entail simply discharging the digestate onto a concrete slab, and allowing the liquid content to run away a drain. Periodically, the solid digestate will accumulate and be removed from the slab either into storage, and subsequent windrow composting carried out (preferred), or into a trailer for spreading directly onto land (not preferred).

Alternatively dewatering may be achieved by using a screw press. In some systems it may be passed through a centrifuge as well.

The digestate liquid contains nutrients and organic matter and may possibly be used as a fertiliser, however, the liquor from all but agricultural waste is usually still classed as a waste material, meaning that it cannot be spread on land as a fertiliser. In such cases, it will be disposed of to sewer after further aerobic treatment to reduce the presence of ammonia, BOD and COD etc. This is very expensive, and is a cost which is frequently underestimated by biogas plant designers.

The big gain from the system is of course the production of energy from biogas. Energy can be readily seen to be a premium product. Everyone needs an uses energy. It’s one of the best products you could ever wish to market in today’s society! You can burn it make heat, burn it to make heat and electricity, or you can upgrade it. In this context upgrading means that by the removal of the carbon dioxide in it and other impurities, to achieve a standard of purity that allows it to be compressed and as it is then in all respects identical to standard compressed natural gas (CNG), it can be injected into natural gas pipelines.

Although this description approximates to what will be found in all biowaste , each contractor holds their own special and often patented design and will introduce their own variations on the above. In anaerobic digestion of Biowaste you will see probably the biggest of all variations in the systems used. There are probably now several hundred biogas companies and each has their own variant on standard anaerobic digestion system designs having built their own systems.

Comparison with the Early Days of the Motor Industry

In such a young industry as this there is a lot of parallel development going on. It can be compared with the situation in the motor industry up to the 1960s. In those days cars had to clutch control, brakes and accelerator leavers in a variety of positions. Each manufacturer has its own idea about the best way to do things. No one system have been proven to be the best, but over many years and many models the industry arrived at the point is today, where anyone can jump into a car from one manufacturer to another, and expect to find brakes, clutch and accelerator in the same position. This is the situation right now in the anaerobic digestion industry worldwide, but just as the motor industry matured into a general acceptance of the one best way to do things, similarly the AD industry will evolve.

It is to be hoped that there will be other close parallels with the motor industry. Just imagine how much more efficient and easier to maintain, control and use the motor cars of today are, in comparison with the first horseless carriages. Anaerobic digestion systems are so new that they are in any horseless carriage stage right now. Never say that anaerobic digestion won’t be the answer to society’s need for energy and raw materials for industrial chemical production. If you do, you’ll be in danger of making the mistake that people made at in the first days of the motor car, by in some countries a man walked ahead waving a flag. Many people said that the motor car was a gimmick and a fad, in those days. Would any person say that now?

Always, remember this comparison, before you say that anaerobic digestion won’t work!

Anaerobic Digestion Plant Output Quantities


Just how much output of and energy from biogas can be achieved, is an often asked and crucially important question, when planning a biogas project. Most feasibility studies conducted for biogas plants are based upon an assumption that the cost of disposal of the resulting digestate will be neutral. That being the case there will be only two sources of income.

The first will be the gate fee and that will be assessed by researching for each project by talking to council waste disposal officers, and business managers within those companies who have organic waste they wish to dispose of locally.

The second and the only one that we can discuss in general terms here, is the output of biogas, and how much revenue that can produce is therefore essential question. In many cases, it will be the only income source of that his controllable by the plant management, as they will be able to choose whether to sell the raw biogas, or process it further into the product commanding a higher price. What the biogas plant opertor can get in payment per cubic metre for the raw gas can only be assessed by finding a local buyer and negotiating a price.

The mount of biogas any particular biowaste will produce varies greatly depending upon the technology used, however, it is most common for gas production rates to be in the range of 70 to 120 cubic metres per tonne. Furthermore, biogas contains something like 55 percent methane. It is solely the methane present that contributes to the energy value. At 55 per cent methane content the energy content of the raw biogas is approximately 21 MJ/m3.

Before that can be calculated as a net output of biogas energy that can be sold, it is necessary to deduct the sacrificial loads which will be used to run the biogas plant itself. As a rule of thumb between 20% and 1/3rd of the energy the plant generates will be required to power the process itself.

For example, if a plant was to process 20,000 tonnes per annum of biowaste, it would be able to export to something like 400 kW of electricity and in addition 750 kW of heat created in producing the electricity. The feasibility of using the heat produced by the gas engine when generating the electrical power varies greatly. Often, there is no readily available user for the heat, in which case a standard air-cooling radiator system is normally installed. However, with suitable investment a CHP system in which hot water is piped, for example, into a number of small businesses to provide heating nearby, the waste heat can be sold very profitably. Of course, by adding CHP the overall carbon footprint of the AD plant rises further, and this can be an advantage for the owning company if it wishes to show off its “green” credentials.

Alternatively it has been suggested that the gas might be processed to produce diesel fuel, in which case it would provide 1.4 million litres of diesel fuel each year.

If the compost was also to be sold it would provide an income. The quantity of compost produced again varies greatly, but a rule of thumb used here would be to assume that 40 to 70 percent of the feedstock input will become compost (fibre). After further aerobic windrowing of the compost from , and (screening) sieving, can be solved into any local market which exists for selling aerobic compost. therefore, assessing the local market for anaerobic compost will provide a guide as to the saleability and value of the fibrous output from a biogas digester.

Contaminants and unwanted materials are removed from the feedstock at the start and during screening of final compost. These are usually called “rejects”, and as the disposal will cost the biogas plant operator it is necessary to quantify the amount of this material, which will probably have to be sent to a landfill. It is hard to generalise the proportion of the compost which will arise as reject material. All that can be said that the reject material typically comprises between 1 and 10 percent by weight of the total compost produced.

The quantity of liquid digestate, not including additional liquid added if needed to improve pump-ability, and not including any additional liquid added to avoid excessive nitrogen/ammonia present within the digester, will be as a “rule of thumb”, between 10 and 30 percent by mass, of the input waste feedstock tonnage.

The liquid digestate created by the digestion of waste materials which include MSW food, is by default deemed not suitable for use as a fertiliser of any crops in te UK. As a consequence, while this remains the situation in the UK it is almost impossible to sell it. However, it is known that the UK government department Defra, appreciates that this is a problem and is endeavouring to change the regulations about this.

Until alternative methods of using the liquor from MSW, such as to fertlize hydroponic systems, use it in aquaculture, or simply concentrate it and further purified it as fertilizer-crystals, it will need to be further treated before being discharged to the sewer. A formal discharge consent is of course needed in order to do that.

(Source of all figures provided: Biological techniques in solid Waste management and land remediation; Chartered Institution of Wastes Management, 2009, CIWM Business Services Limited, Northampton, UK, WWW.CIWM.CO.UK)

5 Reasons Why Anaerobic Digestion is Better than Wind Energy

Image of cows shows why flatulence is better than wind
Why flatulence is better than wind

We nearly called this article “why flatulence () is better than wind”, but we decided that it was a little bit too flippant for such a serious subject. There are in fact that least five reasons why as an energy source, is better than . We know that statement might surprise our readers, and if that is you to read on, and we hope you will think differently by the end of this article.

1. The most important fact that outstrips all others, and we make no apology for placing first in in our list, is that AD Plants generate electricity 24 hours every day. A reliable and well run anaerobic digestion plant will provide a base load of electrical power 24/7 and 365 days a year, every year.

Until technology finds a low-cost and reliable way to store electricity, or to store energy which is ready on-tap for use on-demand, when people want to use it, it will remain necessary to maintain fossil fuel generating capacity alongside all the wind farm capacity.

The true cost of wind energy should therefore be calculated on the basis of the cost of the wind energy itself, plus the cost of maintaining a fossil-fuel powered power station capable of delivering the energy of the wind farm, and to do that while being on-call at a moment’s notice, ready for when the wind stops.

Although, the reserve backup capacity may not need to be 100% of the wind farm generating capacity, if the power grid extends over an extremely large geographical area. The above reserve capacity then provided, can only be less than 100%, if it can be shown that there will be no occasions when all wind farms in the grid feed area, would never all be becalmed simultaneously.

Winter farm subsidies, are not based on this presumption and therefore are subsidized at an unrealistically high level by governments. By contrast, anaerobic digestion power, due to its continuous baseline supply capability, holds none of these hidden costs. Which also include, the use in the case of wind energy, unsustainable energy in the form of carbonaceous fuel consumption.

2. Anaerobic digestion is better than wind farms, because most anaerobic digestion consumes waste, this waste would have harmful consequences if it was not digested. Clearly some wastes are more hazardous to the environment than others. The biggest advantage to the environment when a waste is digested comes from digesting food waste. Food waste increases the risk that the environment will be damaged by polluting emissions if it is placed in landfills. However, all of organic waste is less hazardous to the environment once it has been digested. Not only that, anaerobic digestion contains a pasteurization stage during which it is sanitised and any pathogens present, and seeds, will be killed.

3. A wind farm, once it has been constructed and commissioned, provides very little in the way of jobs for local people. By contrast, an anaerobic digestion plant will require at least one, possibly more, plant operators for as long as it is in use.

4. The turbine blades at wind farms provide a hazard to birdlife. An anaerobic digestion plant does not provide any hazard to birdlife.

5. The motion of wind turbine blades produces noise which can be heard over very long distances. An anaerobic digestion plant, may produce some noise which is potentially audible to those within about 50 metres of an AD plant. Noise nuisance from AD plants is orders of magnitude less intense.

Anaerobic digesters, can be described as able to kill three birds with one stone, because they produce renewable energy, treat waste, and provide a valuable agricultural fertilizer.

It would be a little bit unkind, to say that winter turbines only in comparison, kill three birds with one blade! However, the reader will by now have picked up the views of the author in respect of wind energy… All the author would ask of governments which promote wind energy, that they set tariffs and other incentives at a level which reflects the fact that wind energy is not such a good (nor economic) provider of energy as it might appear to be at first sight.

To give incentives to wind energy which are comparable to, or greater than, anaerobic digestion facilities is illogical. So, we return to where we started this article and repeat that; “flatulence, not wind, is the way to go”.