|MadSci Network: Chemistry|
Hi Katrina, It is well known that horse manure left standing will slowly give off methane gas. However, this does not mean it contains a significant quantity of trapped methane gas that somehow could be extracted or collected. The gas is formed by the gradual decomposition of the organic (carbon containing) material by anaerobic microbes whose byproduct is methane gas. This fermentation process has been studied and optimized and one can buy an apparatus which allows the evolved methane gas to be collected over time or used for heat. The following website: http://www.commonlink.com/~methane/indepth.html gives some information about a commercially available device that does this. According to the website, the optimum temperature for the fermentation is 95F and the output is 3-4 cubic feet of methane per cubic foot of "slurry" per day. Keeping the slurry warm and productive requires energy and mixing. If the system is not well insulated the energy required to maintain the optimum temperature could exceed that available from the methane produced. Interestingly, oil companies are now investing resources in figuring out how to tap the vast deposits of methane that is trapped as water clathrates in the deep ocean. If this can be done efficiently, it would be a new source of fossil fuel and put off the world's eventual need to find a truly alternative energy source. Hope this helps! Jeremy.
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