Benefits of Methane Digesters
Animated presentation of digester benefits.
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 utility, a farm can go off grid and produce its own electricity potentially offsetting $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. Here is video from an experienced nutrient manger.
- excess phosphorus can lead to serious environmental problems in water bodies such as Lake Champlain in Vermont and New York state (USA). With a digester, manure management becomes more flexible. Phosphorous is somewhat concentrated in the solids separation process. Excess and used bedding solids from biodigesters can now sold and this market is expanding.
- the liquid resulting from the digesting plus separation process has less phosphorus and total solids than separated raw manure and is also more plant available. This means less chemical fertilizer must be purchased.
- when combined with modern field spreading techniques, like drag lining and injection, digesters can offer major water quality benefit. It is outlined here in our “Watershed Digester” concept.
- 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.