|MadSci Network: Microbiology|
The production of methane from animal wastes is a complex process involving many organisms from many different species. The basic process can however be broken down into 2 basic distinct phases. 1st, there are a range of organisms that ferment the large carbohydrate based wastes down into smaller acidic wastes. For example glucose can be fermented to formate, hydrogen gas, acetate, propionate, butyrate, ethanol, acetone etc. These organisms are generally anaerobic bacteria and these reactions occur for the most part in the absence of oxygen. 2nd, these products can then be used by another physiological group of organisms, the methanogens that actually produce the methane from these acidic compounds. These reactions are found anywhere that oxygen is absent. Classic environments for methanogensis are swamps, anaerobic sewage digesters, dead trees, anything that is water logged, the guts of animals such as us, horses, termites, and refuse sites. These organisms are therefore present everywhere that oxygen is absent and carbohydrates are present. This is why today refuse sites collect the methane produced. If you want to work or examine these organisms, you therefore have to develop methods to work in the absence of oxygen because not only do these organism need oxygen to be absent for them to grow but it is highly toxic to them binding to their enzymes and killing them. If you wanted to work with these bacteria you can isolate them from any marsh but you need methods to get rid of any oxygen, and as our atmosphere contains 21% oxygen this can be difficult. You can see the work of methanogens however easily in the wild. When you stand on a waterlogged march and the gas bubbles rise, these are a mixture of carbon dioxide and methane. You can even repeat Volta's famous methane experiment. If you are really interested in methanogensis a book I recommend you look at is Brocks Biology of Microorganisms which has a lot of information about the process. Finally is it feasible to fermenter animal wastes to methane? Yes thatís what a sewage plant does with its anaerobic digesters but it can be technically difficult.
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