biog:biogas

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biog:biogas [2025/12/05 15:02] – [Further resources] Dave Darbybiog:biogas [2026/03/26 18:54] (current) – [Further resources] Katja Durrani
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-# Biogas+This topic is part of [[gt:gardening|Gardening, smallholding & farming]] and [[gt:power|Power & heating]]. 
 +====== Biogas ======
  
  
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-## What is biogas?+===== What is biogas? =====
  
 Biogas is mostly methane (around 60%) with carbon dioxide (around 40%) and a little hydrogen and hydrogen sulphide. It's made by anaerobic bacteria breaking down organic matter in the absence of oxygen (e.g. underwater). The process also occurs in landfill sites, and in the digestive system of humans and other animals (yes, farts are biogas). Biogas is mostly methane (around 60%) with carbon dioxide (around 40%) and a little hydrogen and hydrogen sulphide. It's made by anaerobic bacteria breaking down organic matter in the absence of oxygen (e.g. underwater). The process also occurs in landfill sites, and in the digestive system of humans and other animals (yes, farts are biogas).
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 <caption> <caption>
-Small experimental biogas digester. Waste material is put into the oil drum; the neoprene cover rises when full of gas; the gas is tapped into a container (upside-down plastic drum with water seal) which rises as more gas enters. When full, gas can be tapped off and used via a little gas ring. +_Small experimental biogas digester. Waste material is put into the oil drum; the neoprene cover rises when full of gas; the gas is tapped into a container (upside-down plastic drum with water seal) which rises as more gas enters. When full, gas can be tapped off and used via a little gas ring._
 </caption> </caption>
  
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 <caption> <caption>
-Mini-biogas experiment, working on exactly the same principle as the digester above.+_Mini-biogas experiment, working on exactly the same principle as the digester above._
  
 </caption> </caption>
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-## What are the benefits of biogas?+===== What are the benefits of biogas? =====
  
-### Reduces CO2 emissions+==== Reduces CO2 emissions ====
  
 Because it’s a substitute for natural gas. Because CO2 from biogas is from recently-alive plant matter (even if it was fed to animals), it’s part of a cycle – i.e. CO2 given off by burning biogas is absorbed by plants that will provide future biogas, and so on. Because it’s a substitute for natural gas. Because CO2 from biogas is from recently-alive plant matter (even if it was fed to animals), it’s part of a cycle – i.e. CO2 given off by burning biogas is absorbed by plants that will provide future biogas, and so on.
  
-### Reduces methane emissions+==== Reduces methane emissions ====
  
 Animal agriculture is responsible for [around 36% of methane](https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane) released into the atmosphere by human activity. When methane is burnt it releases CO2, but methane is around 30 times more potent as a greenhouse gas than CO2, so it’s a good idea to capture and burn it rather than release it. It’s better for organic waste to be separated and put into an anaerobic digester instead of collecting methane from landfill sites, as nutrients are lost in toxic leachate. Animal agriculture is responsible for [around 36% of methane](https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane) released into the atmosphere by human activity. When methane is burnt it releases CO2, but methane is around 30 times more potent as a greenhouse gas than CO2, so it’s a good idea to capture and burn it rather than release it. It’s better for organic waste to be separated and put into an anaerobic digester instead of collecting methane from landfill sites, as nutrients are lost in toxic leachate.
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 <caption> <caption>
-Simplified cross-section of a type of digester used for animal and human waste all over China and the far east. A toilet can be incorporated into this system.  Image: [Tkarcher](https://upload.wikimedia.org/wikipedia/commons/2/28/Biogas_plant.svg), [CC BY-SA](https://creativecommons.org/licenses/by-sa/4.0/)+_Simplified cross-section of a type of digester used for animal and human waste all over China and the far east. A toilet can be incorporated into this system.  Image: [Tkarcher](https://upload.wikimedia.org/wikipedia/commons/2/28/Biogas_plant.svg), [CC BY-SA](https://creativecommons.org/licenses/by-sa/4.0/)_
  
 </caption> </caption>
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 </figure> </figure>
 </WRAP> </WRAP>
-### Reduces resource use+==== Reduces resource use ====
  
 Producing and using biogas locally means that we don't need millions of miles of pipes to deliver it, and it doesn't need to be liquefied and shipped across the world, with all the resources and energy that these things entail. Plus it saves trees (for firewood). Natural gas is finite, so won't last forever – and there will probably be wars for it as it runs out. Producing and using biogas locally means that we don't need millions of miles of pipes to deliver it, and it doesn't need to be liquefied and shipped across the world, with all the resources and energy that these things entail. Plus it saves trees (for firewood). Natural gas is finite, so won't last forever – and there will probably be wars for it as it runs out.
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 </WRAP> </WRAP>
  
-### Creates two renewable resources+==== Creates two renewable resources ====
  
 Sewage sludge and animal slurries usually end up as fertiliser anyway, so it's better to obtain fuel from it first, and prevent runoff and methane emissions at the same time – and you still get fertiliser at the end of the process. It's the missing link for those wanting to switch from fossil fuels – many people heat their homes with [wood](/wstov/wood_stoves) and their water with [solar](/watr/water), and get their electricity from [wind](/wind/wind_generators) and [solar](/soel/solar_electricity) – but cooking is a problem; it's too expensive with electricity, and Agas are expensive too, plus they take a long time to get up to temperature, and will make your space too hot in the summer. Gas is best for cooking, but with biogas it can be done without gas bills. Sewage sludge and animal slurries usually end up as fertiliser anyway, so it's better to obtain fuel from it first, and prevent runoff and methane emissions at the same time – and you still get fertiliser at the end of the process. It's the missing link for those wanting to switch from fossil fuels – many people heat their homes with [wood](/wstov/wood_stoves) and their water with [solar](/watr/water), and get their electricity from [wind](/wind/wind_generators) and [solar](/soel/solar_electricity) – but cooking is a problem; it's too expensive with electricity, and Agas are expensive too, plus they take a long time to get up to temperature, and will make your space too hot in the summer. Gas is best for cooking, but with biogas it can be done without gas bills.
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 <caption> <caption>
-Adding food waste to a small digester.+_Adding food waste to a small digester._
  
 </caption> </caption>
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-## What can I do? +===== What can I do? ===== 
-### Setting up+==== Setting up ====
  
 Batch digesters based on some kind of drum / container are feasible on the domestic scale. Continuous digesters are popular in Asia - an inlet and outlet pit with a concrete or steel gas container. You can build your own – see our resources for books, links and courses. Batch digesters based on some kind of drum / container are feasible on the domestic scale. Continuous digesters are popular in Asia - an inlet and outlet pit with a concrete or steel gas container. You can build your own – see our resources for books, links and courses.
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 </WRAP> </WRAP>
  
-### Sizing+==== Sizing ====
  
 In India, for a family of 8 with a few animals (say 8-10 cows), a 10m³ digester is recommended, with 2m³ gas storage. But a typical small family digester will be around one cubic metre. For cooking and lighting, you don't need much. Every kg of biodegradable material will yield around 150 litres of gas, and gas lights need around 100l per hour. 2 gas rings for a couple of hours a day will use between 1-2 m³, so if you have some livestock, plus kitchen and human waste, you can do this easily. When it comes to driving any kind of engine (e.g. a generator or a pump) it's a different matter, and is way beyond the domestic-scale. The average amount of time that material stays in the digester before emptying is around one month, and in fact the minimum by law in the UK is 28 days. In India, for a family of 8 with a few animals (say 8-10 cows), a 10m³ digester is recommended, with 2m³ gas storage. But a typical small family digester will be around one cubic metre. For cooking and lighting, you don't need much. Every kg of biodegradable material will yield around 150 litres of gas, and gas lights need around 100l per hour. 2 gas rings for a couple of hours a day will use between 1-2 m³, so if you have some livestock, plus kitchen and human waste, you can do this easily. When it comes to driving any kind of engine (e.g. a generator or a pump) it's a different matter, and is way beyond the domestic-scale. The average amount of time that material stays in the digester before emptying is around one month, and in fact the minimum by law in the UK is 28 days.
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 <caption> <caption>
-Biogas digester on a family farm in India; there’s no reason that they can’t be used successfully in the West too.+_Biogas digester on a family farm in India; there’s no reason that they can’t be used successfully in the West too._
  
 </caption> </caption>
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 <caption> <caption>
-Boiling water with biogas.+_Boiling water with biogas._
  
 </caption> </caption>
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 </WRAP> </WRAP>
  
-### Use+==== Use ====
  
 The waste input must be a slurry – so add water if it’s too solid. Anaerobic microbes operate at 3 temperature ranges, the most common being mesophilic – around 37-42 ºC. In hot climates, digesters can operate at ambient temperatures while in colder countries the digester will need insulation and heating (which could be provided by biogas) If the digester is well insulated, the parasitic load (the amount of energy used to run the system) will be between 15-30%. A [greenhouse](http://lowimpact.org/topics_greenhouses.html) is a good place for it. The waste input must be a slurry – so add water if it’s too solid. Anaerobic microbes operate at 3 temperature ranges, the most common being mesophilic – around 37-42 ºC. In hot climates, digesters can operate at ambient temperatures while in colder countries the digester will need insulation and heating (which could be provided by biogas) If the digester is well insulated, the parasitic load (the amount of energy used to run the system) will be between 15-30%. A [greenhouse](http://lowimpact.org/topics_greenhouses.html) is a good place for it.
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 <caption> <caption>
-Temperature range for microbes.+_Temperature range for microbes._
  
 </caption> </caption>
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 </WRAP> </WRAP>
  
-### Regulations+==== Regulations ====
  
 In the UK, the Environment Agency has several exemptions that enable micro AD to be operated without a permit. These free exemptions area easy to apply for as long as the plant and use of digestate fall into certain criteria. Where feedstock contains animal by-products the process to get AD plants approved is fairly lengthy and rigorous with some cost attached. However, non-commercial plants are not mentioned. Also, these regulations vary from country to country (even within the UK) so if in doubt, check with your local regulators. In the UK, the Environment Agency has several exemptions that enable micro AD to be operated without a permit. These free exemptions area easy to apply for as long as the plant and use of digestate fall into certain criteria. Where feedstock contains animal by-products the process to get AD plants approved is fairly lengthy and rigorous with some cost attached. However, non-commercial plants are not mentioned. Also, these regulations vary from country to country (even within the UK) so if in doubt, check with your local regulators.
  
-### Safety+==== Safety ====
  
 Methane is explosive – see [Adelaide University's website](https://web.archive.org/web/20140325204535/http://www.adelaide.edu.au/biogas/safety/) for safety considerations. Methane is explosive – see [Adelaide University's website](https://web.archive.org/web/20140325204535/http://www.adelaide.edu.au/biogas/safety/) for safety considerations.
  
  
-## Further resources+===== Forum ===== 
 + 
 +This topic belongs to the section [[gt:gardening|Gardening, smallholding & farming]]. You can ask questions or add information on the corresponding [Forum section](https://forum.growingthecommons.org/t/gardening). 
 + 
 +It is also in the section [[gt:power|Power & heating]] (Forum: [Power & heating](https://forum.growingthecommons.org/t/power)). 
 + 
 +===== Further resources ===== 
 + 
 +- [Anaerobic Digestion (AD)](https://www.biogas-info.co.uk/) - Information Portal on Anaerobic Digestion 
 +- [Energy Justice Network](https://energyjustice.net/) - anti-landfill gas site 
 +- [Biogas Technology](https://biogas-technology.blogspot.com/2012/10/biogas-plant-construction-plant-guide.html) - small biogas plant construction guide 
 +- [Build a Biogas Plant](https://www.build-a-biogas-plant.com/) - anti-landfill gas site 
 +- [Open Ideas](https://www.lowimpact.org/wp-content/uploads/Open-Ideas-Domestic-biogas-projects-in-developing-countries.pdf) - domestic biogas plants in developing countries 
 + 
 + 
 +===== Related topics =====
  
-- ## [Anaerobic Digestion (AD)](https://www.biogas-info.co.uk/) - Information Portal on Anaerobic Digestion +- [Septic tanks & drainage fields](sept:septic_tanks) 
-- ## [Energy Justice Network](https://energyjustice.net/) - anti-landfill gas site +- [Low-impact energy](lien:energy) 
-- ## [Biogas Technology](https://biogas-technology.blogspot.com/2012/10/biogas-plant-construction-plant-guide.html) - small biogas plant construction guide +- [Compost toilets](cptt:compost_toilets) 
-- ## [Build a Biogas Plant](https://www.build-a-biogas-plant.com/) - anti-landfill gas site +- [Composting](cpst:composting) 
-- ## [Open Ideas](https://www.lowimpact.org/wp-content/uploads/Open-Ideas-Domestic-biogas-projects-in-developing-countries.pdf) - domestic biogas plants in developing countries+- [Cattle](catl:cattle) 
 +- [Smallholding](smho:smallholding) 
 +- [Low-impact sewage treatment](sewg:sewage) 
 +- [Low-impact cooking](lico:cooking) 
 +- [Keeping livestock](livs:livestock)
  
-## Specialists+===== Specialist curators of this topic =====
  
  • biog/biogas.1764946976.txt.gz
  • Last modified: 2025/12/05 15:02
  • by Dave Darby