When it comes to on-farm methane production, more people are thinking "small."
A California company has developed a manure-digestion/methane-production system that it says can work on dairy farms with as few as 100 cows. Meanwhile, UW-Extension recently sponsored an internet seminar - or "webinar" - that looked at making simple manure digestion systems that can provide enough methane gas to cook a couple of meals and heat water each day.
For years, commercial, on-farm methane production systems have been geared' to larger farms - those with 800 cows or more. But Avatar Alternative Energy, Walnut Creek, Calif., has developed what it calls a "scalable" setup. That is, it can work for farms with as few as 100 cows all the way up to approximately 1,200.
The methane produced by anaerobically digesting the manure from 100 cows won't go terribly far in meeting a farm's total energy needs, says an Avatar representative. But that methane can drastically cut the bill for heating water, for example.
To economically burn the methane in a generator and produce electricity to use or sell will probably require 400 cows or more, the Avatar spokeswoman says. That's because an electrical generator can cost $75,000 or more.
Even so, a digester system for 100 or more cows can help a farmer gain valuable experience with the whole manure-digestion, methane-production process. Then the system can be enlarged later. That's easy to do with the Avatar technology, says the company representative. It goes back to "scalability."
At the heart of the Avatar arrangement is a fiberglass cylinder that's eight feet high and approximately 80 feet long. Manure is heated, then pumped hydraulically through a series of baffles. After 21 days in the cylinder, anaerobic bacteria have created methane gas.
If a farmer wants to digest more manure and get more methane, he or she only has to add another cylinder. Need still more capacity? Add another cylinder or two.
