A sealed tank turns decomposition into fuel
Fresh manure contains organic material that microbes can break down. In an anaerobic digester—an airtight tank without oxygen—microbes do that work and release biogas, a mixture made mostly of methane and carbon dioxide. Because the gas is collected rather than allowed to disperse, the methane becomes a usable fuel.
The tank is kept under conditions that let the microbes keep working, while operators feed in manure and remove the partly decomposed material. This is not simply a matter of burning manure: the useful energy comes from methane produced during digestion.
From biogas to electricity
Before use, the biogas may be treated to remove water and contaminants such as hydrogen sulfide, which can corrode equipment. The methane-rich gas is then burned in an engine or turbine. The resulting motion turns a generator, which converts mechanical energy into electricity.
Some facilities also capture the heat from the engine or turbine. Using both electricity and heat can make more of the fuel’s energy useful, for example by warming the digester itself.
The waste still has a job
Digestion does not make the manure disappear. The remaining material, called digestate, can be stored and used as fertilizer, though it still needs appropriate handling. Capturing the biogas also changes what happens to methane that could otherwise escape during manure storage.
The key conversion is therefore a chain: microbes release methane, equipment captures and burns it, and a generator turns that energy into power—while leaving a nutrient-rich material that farms can put back to use.
