Benefits of Methane Digesters
Farms that install methane digesters benefit in multiple ways. One fascinating aspect of developing a digester is that every farm is unique, and the benefits are limited only by the imagination. For example:
- in Europe, Canada and the American state of Vermont farmers can earn more than 20 cents per kW for their electricity. A multi-year power purchase agreement (PPA) from a utility ensures the farm a dependable revenue stream while milk prices fluctuate over time.
- if a low price is offered by the local utility, the farm can go off grid and produce its own electricity, a potential offset of $45,000 at a 500 cow farm.
- larger farms near pipelines can produce RNG (renewable natural gas) which currently provides sky high profits for farmers and developers.
- methane digesters produce heat and this can be utilized in buildings, including homes near the digester. Some farmers use this for other commercial purposes such as heating a greenhouse. See above – engine room at Pennsylvania farm in winter heated by its CHP generator.
- farms near population centers can co-digest food processing and other organic waste with their manure. This increases the digester’s energy output while haulers who deliver waste typically pay tipping fees of $15 or more per ton. If the farm adds a “de-packager”, fees can be much higher. Several American states have laws mandating organic waste be taken to environmentally friendly systems like methane digesters.
- a major annual expense (e.g. $45,000 for a 500 cow farm) is bedding. A methane digester typically produces twice the amount required by that farm. Quality, low pathogen, largely odor free bedding increases cow comfort – and cow comfort means more milk. Digester bedding also helps protect the herd from costly mastitis infections.
- excess phosphorus can lead to serious environmental problems in water bodies such as Lake Champlain in Vermont and New York state (USA). With agricultural digesters, phosphorous can be somewhat concentrated in the primary solid separation process, and to an even great extent in a secondary solids system. Excess primary and secondary solids from biodigesters are now being sold and this market is expanding.
- separated liquids from the methane digester process have less total solids than separated raw manure and are more plant available. This means less chemical fertilizer needs to be purchased.
- young pig populations can be destroyed by an unexpected loss of heat. An anaerobic digester can ensure this does not happen and the farm remains economically viable.
- wealthy homeowners and schools sometime threaten legal action against nearby farms due to manure odors. A digester reduces these by as much as 90% making the farm a good neighbor to both.
- some farms even press digested solids in a mold to create flower pots. Material that was formerly manure, now a profitable product.
Reviewing this list you can see the many benefits of a methane digester. Creative farmers and developers regularly discover new ones.