Biogas is a gas, which precipitates out as a result of anaerobic (without access of air) fermentations of organic mass under influence of special bacteria. Composition of biogas is close to composition of natural gas as natural gas has on one of versions a similar origin. Briefly about biogas it is possible to read through in Wikipedia..
     Accordingly, to use biogas it is possible in the same way, as well as natural gas. It can be burnt in cookers and heating devices. It can be processed in an electricity in cogeneration installations. It can be compressed, pumped in balloons and used as fuel for internal combustion engines of cars.
     It is necessary to remember only, that sometimes biogas happens is polluted by hydrogen sulphide which causes corrosion of metal and clogging of nozzles of gas devices. Therefore biogas sometimes is necessary for refining before utilization, except for utilization in expressly intended for processing biogas cogeneration installations.
     Before shrinkage and pumping in balloons biogas is desirable for purifying of a carbon dioxide.
     Composition of harmful impurities in biogas depends on a feed stock from which biogas is made, therefore necessity and composition of systems of purification of biogas depend on a concrete site and application of biogas installation.
     For small and medium biogas installations is economically inexpedient to transform it to an electricity, or to compress and pump in balloons. Typical application in this case are heating rooms, preparation of a steam, preheating of water, cooking.
     It is necessary to notice, that in calculating of economic efficiency of biogas installation economic benefit of made biogas makes only 10-20% of the common economic benefit. The basic economic benefit is received from utilization of made biofertilizers.