[[Image:biogas pump.jpg|thumb|right|300px|Biogas irrigation pump. Photo: [http://www.flickr.com/photos/djfulford/3156710354/in/set-72157612011013426 d.j. fulford.]]]
Using biogas for pumps in irrigation is gaining in popularity in India and elsewhere, as the savings in petroleum fuel prices are great. However, the cheapest way to get biogas, is to build a biomass digester, which means biomass must be collected, cultivated, or found. Biomass, in the form of firewood, charcoal, agricultural residues, or dried animal dung is already the main energy resource for the majority of the poorer half of humanity, over 2 000 million billion people. They currently use 15% or more of total world energy, entirely in the form of biomass. Certain poorer countries depend on biomass fuels at present for over 90% of their energy needs (i.e. mainly for cooking fuel). It has been estimated that 53% of energy use in Africa, 17% in Asia and 8% in Latin America is currently met from biomass resources. Therefore biomass is already a huge and vital economic resource, although it is usually informally exploited mainly for cooking purposes and still remains rarely used for the production of shaft power via heat engines, and even less so for irrigation pumping. But using biogas for pumps in irrigation is gaining in popularity in India However, more and elsewhere, as the savings in petroleum fuel prices are great. To get biogas, build a biomass digester. Farmers more farmers are using cow dung to create biogas or communities are using toilets to recycle their excrementin their own bio-digesters.
Because biogas digesters have the capability of storing at least a 12-hour supply of gas, an engine can be used that draws gas at quite a high rate. In fact the size of engine is not critical since it is only the number of hours it will run that are governed by the digester gas capacity.
The main problem with biomass as a fuel is its uneven distribution, being most available in forested regions where it is little needed. Considered as a global resource there is no shortage of biomass, since:<br>
* The world's annual usage rate of use of energy is only about 10% of the annual natural rate of photosynthetic energy storage (i.e. solar energy stored in plant matter); stored .* Stored biomass on the earth's surface at present is approximately equivalent to the entire proven fossil fuel reserves (oil, coal and natural gas).
This issue of food versus fuel is an important one, but where the fuel crop is used for irrigation pumping to produce food crops, especially in a small-scale "on-farm" process, the same objections need not apply.
The country which has made by far the most use of biogas production in agriculture is China, where, particularly in Sichuan province, there are several million working biogas units. This development took place almost entirely within the last 10-15 years. Various studies (eg. [86]) have indicated that the The value of the fertilizer output usually surpasses the value of the energy produced by the process in China. The waste disposal and sanitation aspects of the process are also important justifications for its use.