Biomass CHP (AD)
Biogas refers to methane gas produced by the biological breakdown of organic matter without oxygen. This process can take place in specially designed anaerobic digesters but also takes place in landfill sites.
More information on Biomass CHP (AD)
If organic matter is allowed to rot in the absence of oxygen, it turns into biogas which is 60 per cent methane and 40 per cent CO2. This can be burnt in combustion appliances to produce heat and electricity as well as a digestate which can be used as fertilizer or soil improver (spreading of digestate can be subject to licencing from the Environment Agency). Biomethane is a biogas which is concentrated to the same standards as natural gas. Most anaerobic digestion plants are small scale and are work at low temperatures, serving single farms. The economics of biogas tend to favour either sites that can provide their own feedstock (manure, municipal putrescible waste, crops such as maize etc.) or large installations that can sign significant contracts for feedstocks. When derived from a waste source, biogas can be one of the most sustainable energy sources. However, if not properly designed AD can have smell implications which make it difficult to reconcile with new property development in many cases. The disposal of digestate also needs to be considered.
Summary
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Biogas is a mixture of methane and CO2 from anaerobically digested plant material. Feedstock could be sewage slurry, animal slurry, food chain waste or energy crops.
- Capacity factor: up to 90 per cent
- Constraints: feed stocks, smell implications, needs to be of large scale to be economic
- Advantages: excellent example of closed-loop resource use, can exploit waste resources
- Typical lifetime of a generation plant is expected to be 10-15 years, longer for digesters
Examples
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Biogas CHP at South West Water http://www.energ.co.uk/?OBH=730&ID=436
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Holsworthy AD Plant in Devon (proposed heat distribution system not connected)
- Jühnde Energy Village (Germany) http://www.regbieplus.eu/265.0.html
- Vaxtkraft, Sweden: Case Study - The Vaxtkraft Project, Vasteras, Sweden (PDF 308 KB)
Links
- Technical summary: Regen SW Anaerobic Digestion Information Sheet (PDF 124 KB)
