The value of energy in manure can be captured on the farm or by selling manure to someone else for the purpose of extracting the energy. Perhaps the most familiar method of extracting energy on the farm is the capture of biogas from anaerobic digestion of liquid manure. The biogas contains a high proportion of methane that can be burned to produce heat or be used to fuel a generator or both. See this article for more information on digesters: Economics of Anaerobic Digesters for Processing Animal Manure.
The value of energy extracted on the farm may be realized as income or as savings of purchased energy and the value of increased productivity. Income from energy extracted from manure on the farm may result from electricity generated from biogas and sold to an electric power company or utility. Savings may result when LP (liquid propane) gas is no longer required for heating or electricity is no longer purchased by the farm. Recent examples of capturing the value of energy from manure by selling the manure include the large-scale manure combustion plants . In one example, poultry litter is burned to provide energy for steam turbines to generate electricity.
The combustion of manure from a large feedlot to provide energy for ethanol production on site is another example of capturing the value of energy in manure. In this case, the manure may be sold to the ethanol producer or may be retained by the feedlot operator who would extract the energy. When the manure is burned for energy, of course, the fertilizer replacement value of the nitrogen it contains is lost and no longer available for crop use. That loss should be weighed against the value of the energy produced.
Other resources on energy capture from manure include: