Thursday, May 23, 2013
By BEN McCANNA Morning Sentinel
(Continued from page 1)
Adam Wintle, left, Travis Fogler and John Wintle walk past the digester buildings where food waste and cow manure are mixed to produce gas that powers a generator for electricity.
Photos by David Leaming/Morning Sentinel
Cows at Stonyvale Farm in Exeter are part of a dairy and energy enterprise.
As the mixture breaks down in the digesters and the pressure subsides, the system's computer automatically pumps more raw manure and food waste into the containers to keep the bacterial process rolling. At the same time, spent material is pumped out of the containers, where it passes through a mechanical liquid separator. Plant fibers that aren't broken down during the anaerobic digestion process are separated from the water and reused.
All day long, the fibers churn out of the machine in bone-dry clumps that fall into large piles that are used for cow bedding or compost.
The liquid from the separator is pumped back to the farm, where it spills into lagoons that once held raw manure. The liquid contains all the same fertilizing nutrients found in raw manure, but it's better. The liquid is easier to spread on fields than manure; plants absorb its nutrients more easily; and it is virtually odorless, said Wintle, 37.
Those two byproducts save the farm about $100,000 a year, Fogler said. The greatest savings are found in fertilizer costs. It's not that they produce more fertilizer; they can just use more of what they have.
"Manure before digestion stinks, so all summer long we would purchase (commercial) fertilizers because we didn't want to aggravate our neighbors with the odor," said Fogler, 35. "The digestion process removes the odor, so we're able to spread it all summer."
MANURE POWER POTENTIAL
Donna Wagner has lived about a half mile from Stonyvale Farm for the past seven years. She said the odor reduction was immediately noticeable.
"It is less smelly, even during the summer," she said.
In the United States there are about 100 cow-power facilities. Only a dozen combine food waste with manure. In Maine, there is only one.
Curt Gooch, dairy sustainability engineer at Cornell University in Ithaca, N.Y., said digesters first appeared in the U.S. in the 1970s, during the oil embargo; however, when oil prices dropped, interest dried up. Then, in the late 1990s, there was a resurgence. Digesters have continued to crop up since then, but it's still not widespread.
"The potential is huge," he said. "It's a big bud that's waiting to blossom."
In Europe, cow power is in full bloom. About 5,000 anaerobic digesters operate in Germany alone, Gooch said.
But installing cow power requires a substantial investment, which is extremely difficult for U.S. farmers, who are often in the red.
While wind energy projects often are criticized by nearby residents, neighbors of cow power facilities are generally pleased, said Adam Wintle, a managing partner at Biogas Energy Partners who is John Wintle's brother.
Biogas Energy was a development partner for the Exeter project, and manages its finances. The company also is seeking opportunities to bring new cow-power facilities to Maine.
"Socially, environmentally and economically there are so many positives," Wintle said.
Morning Sentinel Staff Writer Ben McCanna can be contacted at 861-9239 or at: