New Mexico has been selected by USDA as one of three pilot states to participate in building 150-200 anaerobic digesters, according to USDA reports. The goal is to construct the digesters over a four-year period through USDA’s Natural Resources Conservation Service (NRCS).
Controlled anaerobic, or oxygen-free, digestion of animal manure is a way to treat manure to prevent odors while generating a usable energy product. Anaerobic digesters break down liquid manure into biogas and a low-odor, anaerobically digested manure or effluent. The biogas can be burned to produce heat, electricity or both, while the effluent can be stored and applied to fields with significantly less odor than stored, untreated liquid manure but with the same amount of nutrients.
New Mexico does not have large poultry or swine producers, but is one of the country’s largest dairy producers. The state has roughly 225,000 dairy cows. NRCS will focus mostly in the south and eastern portions of the state where about 70 dairies are located.
The manure of one cow can power a 100-watt light bulb continuously, according to Chuck Braden, NRCS agricultural engineer in New Mexico. That makes cow manure a significant and continual renewable energy source.
In an anaerobic digester, the manure must be maintained at a constant temperature of at least 100°F for 20 days in order to generate the maximum amount of biogas or methane to power an electric generator. The energy produced can be used where it originated, helping dairies keep operating costs down.
After the compressed biogas is pre-treated, the product can be pumped into existing gas pipelines, from where it can be sold and distributed throughout a multi-state region.