AURORA | There are more than cows behind the red barn walls of Aurora Ridge Dairy.
Humming and grumbling behind them are big pieces of equipment — churns, an enormous 12,400-volt transformer, pipes and an engine. Just outside one of these barns, concealed by a light layer of snow, is the digester, a concrete vat that is 72 feet wide, 242 feet long and 16 feet deep — larger than an Olympic-sized swimming pool.
It is all part of a biogas fuel generator, a networked machine that pumps cow manure into the digester to convert methane gas into electricity. That electricity is used to power the entire farm, from its largest agricultural equipment to the lights in Aurora Ridge's office building.
"Yep, this is powered by manure," said Jason Burroughs, one of the partners of Aurora Ridge Dairy. Burroughs has worked on the farm for 18 years, ever since he was an intern for his current partner, William Cook. "We want to be good stewards of the land, good stewards of the environment. Building the digester was one way of doing that."
Methane is one of the greenhouse gas culprits that has been linked to global warming and climate change. Aurora Ridge Dairy, which has about 3,800 animals on the farm, produces a significant amount of the gas. Through the biogas fuel generator, which officially started operating in September 2009, the farm has reduced its emissions and become self-sustaining.
Despite the benefits, it's an expensive installation — approximately $2 million — and the paybacks are slow.
"It's one of those technologies that's catching on. I would think it would catch on faster if we could get more incentive. It almost makes it impossible to do without help," Burroughs said.
Currently there are 18 such generators on farms in New York state, according to the New York State Energy Research and Development Authority. The U.S. Department of Agriculture and NYSERDA helped Aurora Ridge Dairy pay for its biogas fuel generator with grant money. It took nearly a year to install, and several major adjustments throughout the farm.
At its bare bones, Burroughs described, the digester works like this: Manure is fed into the system every day. It makes a few pit stops: a reception pit, a collection pit, then through a pump that controls how much manure goes into the digester. It reeks to high heaven inside the barns, he said, and steam rises off the digested material, traveling along conveyer belts. Eventually it is pumped to the digester, which heats the manure to about 104 degrees.
"The digester is much like a cow's stomach," Burroughs said. "As you eat food, the bugs digest the food."
There are actually bacteria in the vat, eating the manure, which stays in there for 21 to 30 days. At the top of the digester, a pocket of gas forms. Eventually, the pressure pushes the gas through a pipe, which leads to an engine room. In that room, the magic happens. The gas cools and condenses, and runs through a V16 engine, which generates energy — lots of it. Most of the farm's equipment, which used to run on diesel, now runs on the electricity produced by the biogas generator.
Any extra energy the farm generates is sold back to the grid. Burroughs said they don't make very much, though. The profit is so small that it usually does not cover maintenance of the engine.
"You wouldn't build these to make money," Burroughs said. "Our benefits here have been reduced odors, reduced electric bills and a little bit of sales. We also recycle our manure as bedding."
In the process, the solids and the liquids of the manure separate, and they're heated up to kill pathogens like E. coli. The solids are used as bedding material for the cows, instead of purchasing paper or sawdust. The liquids will be used as fertilizer for crops. Nothing goes to waste.
The biogas generator also indirectly benefits the image of Aurora Ridge. Burroughs said many times people think dairy farmers are still sitting on stools, hand-milking cows.
"When people see all of this, they're amazed," he said.