[[Image:biogas diagram.jpg|thumb|center|600px|A cross-section of a fixed-dome digester. For further information on how this works, and for other types of biogas digesters, see the Practical Answer's [http://practicalaction.org/biogas-answers technical briefs on biogas].]]
==Costs==
'''Cost of bio-digesters:'''<br>
The flexible balloon installations are relatively cheap (30-100 US$), but are liable to damage. Floating drum and fixed dome digesters are more expensive (700-1200 US$), but are more robust. Floating drum installations are effective, providing gas with a fixed pressure, which is good for domestic use, but can be more expensive and less robust than a fixed dome digester. Fixed dome digesters are more robust as they use no moving parts and can be constructed from local materials.
==Reference manuals, videos, and links==
* [http://www.fao.org/docrep/010/ah810e/AH810E13.htm BIOMASS AND COAL (THE NON-PETROLEUM FUELS)] FAO.
* [http://practicalaction.org/biogas-fuel Poo power: cow dung can be used as fuel.] Practical Action.
* [http://www.dfid.gov.uk/R4D/Output/187175/Default.aspx The Potential of Small-Scale Biogas Digesters to Alleviate Poverty and Improve Long Term Sustainability of Ecosystem Services in Sub-Saharan Africa]. Dr J.U. Smith, University of Aberdeen, Institute of Biological and Environmental Science.