Farming Magazine - June, 2010


Become the Utility

Methane digesters power the future
By J.F. Pirro

Today, smart farmers, even retired farmers, like Harlan Keener at Rocky Knoll Farms in Lancaster, Pa., are seeing green as “green energy” farms. Those with foresight, and capital, those who have invested or will be investing in methane digesters, are generating their own electricity. They have become the new energy companies; or at least they have found a way to beat the energy companies in the face of deregulation.

There may not be a better example of modern agriculture in action. The increasing popularity of the evolving technology of anaerobic digestion arrives as changes in regulations make it easier for farmers to sell their power to utilities.

When Keener, a pig farmer, began his pioneering efforts in 1984, he could find only one other digester in the Northeast at the time, and that one was on a dairy farm 20 miles away in Adams County. Another was up and running in a chicken house in Little Rock, Ark. He would have had to go to Iowa to find a digester in use on a hog farm like his, and that one was only partially operational.

In his first five years in operation, though he had numerous requests, he didn’t grant interviews. “You would think I wanted the publicity,” says Keener, now 77, whose son Duane now runs the operation. “It wasn’t until some seminar in Harrisburg [Pa.] that someone finally convinced me: ‘Harlan,’ he said, ‘what you’re doing is too good not to share.’ Then, the dam broke. Everyone from east of the Mississippi and up from the Carolinas came calling.”

He was even invited to speak at the White House during the Clinton-Gore administration. He hosted China’s EPA. “Four of them came from Beijing,” Keener recalls. “In broken English, the one said, ‘Mr. Keener, I like you.’ Two minutes later, she said it again, ‘I like you.’ ‘Well,’ I said, taking a bow, ‘I like you, too.’ Before they left, they said I should come to see the Great Wall of China and their digesters, too. Two days later, the Chinese Embassy called and asked if I would be their guest for 21 days.”

He went, and returned a second time later in his career.

“I have a lot of pride in it,” Keener says of his work with digesters. “I learned a lot of stuff, namely that hog manure is special.”

How digesters work

Wanner’s Pride N Joy Farm in Narvon, Pa., has had a digester since 2007. Designed by RCM Digesters of California, the tank is 16 feet deep and 80 feet in diameter with a working depth of 14 feet of waste product. It holds approximately 500,000 gallons.

Waste flows by gravity to a reception pit where it is agitated and then pumped into the digester tank. As new product is pumped in, digested material flows out by gravity. After digestion, the product is relatively free of weed seeds and harmful bacteria due to the heating (between 100 and 105 degrees Fahrenheit) that occurs during the digestion.

Alfred Wanner, who with his wife Carolynne and two sons, John and Matt, owns and operates the 112-acre, eighth-generation family dairy farm. Some 650 Holstein cows are milked three times a day in a double-12, herringbone milking parlor. The farm produces a tanker truck of milk in a little over 24 hours.

“Our goal is to operate a successful farm business while being responsible stewards for the long-range health of our cattle and land,” Wanner says. “With the construction of a methane digester, [which has been featured on CNN, NBC and the Sundance channel], we are one step closer to that goal. By using waste as an alternative energy source our operation reduces odors, the amount of carbon in the atmosphere and the volume of manure going back to the fields.”

Likewise, since 2007, at Brubaker Farms in Mount Joy, Pa., sons Mike and Tony have joined their father Luke Brubaker in the use of an RCM Digester for their 700-cow dairy and poultry operation. It’s “fed” four times per day with discharges from two free-stall barns that house the milking cows. The solids and liquid are mixed, and then pumped into the digester where the slurry is heated, thus simulating the conditions found naturally within a cow’s rumen. At that point, methane gas is created, captured and sent to a GUASCOR power plant that generates 170 to 190 kilowatts per hour of electrical power.

The methane gas is chilled and filtered to remove any moisture before it goes to the engine that powers the generator. From there, the farm sells the electrical power to the power grid. The “parasitic” load on the system (the energy needed to run the digester) is about 10 kilowatts per hour, and the farm uses about 40 kilowatts per hour. That leaves 130 to 140 kilowatts per hour for the grid.

Additional revenue streams

At both farms, once the digestion process produces the methane gas, the manure solids are removed, dried and reused as cattle bedding. “This light, fluffy material has replaced a mix of sawdust and shavings we previously used,” Alfred Wanner says. “This has offset the purchase of bedding and saved us approximately $4,000 per month against a three-year payback on equipment.”

Alfred Wanner’s Pride N Joy Farm in Narvon, Pa., has had a digester since 2007.
Photo courtesy of Pride N Joy Farm.

At Brubaker Farms, not only is there enough bedding for their own cows, but enough extra to sell to another dairy producer who also has a 700-cow herd.

The liquid that flows from the digester is stored for use on Brubaker’s crop fields as fertilizer, thus helping the farm adhere to new federal field guidelines for nitrogen and phosphorous levels. The nitrogen changes from an organic to an inorganic form. The phosphorous levels reduce.

Odor reduction

Another major benefit to operating a digester is odor control. Operators estimate a manure odor reduction of about 90 percent, and odor control is exactly why Harlan Keener initially built his digester, which measures 28 feet wide, 153 feet long and 17 feet deep. “I have not had one [odor] complaint since the digester,” he says.

In its heyday, Rocky Knoll Farms, which began in 1978, had 13,500 pigs in a farrow-to-finish (birth-to-slaughter) operation on 200 acres. “They made a lot of manure,” Keener says. At its height, the farm was sending out 2.5-truckloads of pigs a week to slaughter. Since 2001, after mold crept into his hog’s feed and spoiled business, he’s sold most of the farm operations except for the farmhouse and 64 acres (even that’s rented), but kept a business interest in the digester.

In the late ‘70s, a neighbor who happened to be the then-district attorney of Lancaster County cried foul because of the smell. “He didn’t mince words,” Keener recalls. “If I stayed, he said he would sue. Then, he went to Stone Harbor [N.J.] for the summer, and that gave me time to scout around [for solutions].”

Keener first learned about methane digesters at an Ag Progress Pork Days event. Now, his digester runs 24 hours a day, seven days a week on a generator. Some 5,000 gallons of manure are pumped in three times a day from about 4,000 hogs that enter as Peter Pigs, or 15- to 20-pounders.

Before the digester, for odor control, Keener used aerators off 15 compressors. They added bubbles of oxygen, but the compressors consumed lots and lots of energy. “What we did now is reverse the flow of energy,” he says.

Often, he generates about 8 gallons of propane from excess heat from the radiator (heat from the exhaust) and uses that to heat hot water.

If his utility bill averages $4,800 a month, especially in the summer months, with the digester, he generates about $5,000 a month in energy sold back to PPL. Some months, he makes $600 profit. Now there are reverse meters that spin backwards to credit farmers like Keener.

Dollars and sense

Keener’s latest conversations with his energy supplier have centered on the changing rates he’ll be paid per kilowatt-hour since deregulation. He used to generate 6 cents, but now the payout is upwards of 13 cents per kilowatt-hour. “It helps me,” he says of deregulation.

There are food companies, too, that need to eliminate or convert industrial waste. He says you don’t need cows or hogs to need a digester. Cheese, and companies like Kraft or Grey Pompon mustard, or even a meatball factory’s excess, will make excellent fuel. The waste has to be tested, and the solids volatile enough, and with the right initial pH, but it’s worth exploration as additional income to offset energy costs.

With a digester, Keener says he always has options for an additional harvest. “What I’m harvesting are BTUs,” he says.

Meanwhile, he continues to get a monthly payout from PAL, from the same digester, albeit a different engine. There are some problems, but “not humongous ones,” Keener says. “Whenever we’re shut down, the worst is a day or two. Usually, we’re up and running again in a couple hours.”

His digester cost $225,000. “It seems like a lot of money, and it was,” he says. He borrowed $25,000 more, too. You can say it was a tax deduction, “but there weren’t any earnings yet,” he says.

Keener leased the digester to the city bank and had his miracle machine paid off in five years. “What really makes it work well is if you have a lot of your own money in it,” he says.

Digesters now cost about $1 million (plus interest).

The Wanners received $465,000 from a PA Energy Harvest Grant and $125,000 from a USDA Renewable Energy Grant (though grant monies are taxable). The Wanners also sold their carbon credits and fuel offsets to Native Energy. This is a 15-year contract based on the first six months’ production for $99,000. They also obtained a loan from the sustainable energy fund for $300,000, then self-funded the balance.

However, while Pride N Joy Farm’s voided energy costs are approximately $3,000 per month, its income from excess sold back to PPL averages $3,500 per month, which is paid on an annual basis.

The author has been published in national and regional magazines as well as daily and weekly alternative city newspapers. A gentleman farmer in Quakertown, Pa., he writes about people, social trends, historic preservation and 18th century America, agrarian culture, land use and sports and recreation topics.