Methane production from farm effluents in France and Europe : principle, inventory and prospects

Methane production is presently expanding in France, due to its environmental advantages (reduced greenhouse effects, production of renewable energy) and to the better price for the electricity from the bio-gas. The process involved, through the action of complex micro-biological transformations, mineralizes part of the organic substances into bio-gas. On the farms, it takes place mainly in a liquid environment, inside reactors thermo-regulated at 35-40 degrees C (95-105 degrees F). To the raw materials from the farms (livestock effluents, silages) are often added waste products issued from the agri-food industries or from communities. A profit is made from the bio-gas thus produced by generating electricity and heat together through ad hoc engines. In France, the prospects for methane production appear to lie between the German model (developed on the scale of the farm, of the digestion of livestock effluents and of maize silage together) and the Danish model (with centralized units treating at the same time effluents from livestock and waste products from industry and from the communities).