Farmers Looking at Methane Digesters to Create Energy from Cow Manure
FREDERICK, Md. In the future, Frederick County residents may power their homes thanks to a few local dairy cows.
Frederick County farmers are assessing the viability of methane digesters on their farms to save money, better utilize their resources and help the environment. Digesters capture gases from cattle manure to turn into energy.
"It's another form of energy available for the community to tap into," said Frederick County Dairy Extension Agent Stan Fultz. Manure is readily available on farms to turn into two end products, electricity or natural gas, while the nutritive value is still available to farmers for growing crops.
"The benefit comes to the farmer in that he can use the power on his own farm to decrease his bills," Mr. Fultz said. Neighbors benefit from a drastic reduction in odor and that renewable energy is being produced right in their own neighborhood. What is methane?
According to the U.S. Environmental Protection Agency's AgStar Web site, methane is a greenhouse gas that remains in the atmosphere for nine to 15 years and is over 20 times more effective in trapping heat in the atmosphere than carbon dioxide.
Methane is a primary constituent of natural gas and a source of energy. Efforts to prevent or utilize methane emissions can provide energy, economic and environmental benefits.
Livestock manure handled as liquid and slurry decomposes anaerobically, which produces gases like methane, the Web site said. In waste management systems like digesters, gases consist of about 70 percent methane. When gases are collected and transmitted to a combustion device like an electric generator, energy is produced.
The components of a digester waste management system include the digester itself, a gas-handling system, a gas use device and manure storage to hold the effluent until it is applied to the land. Dairies often use a solids separator so that solids can be recycled back into bedding or compost, and water is used to irrigate fields.
Three Frederick County dairy farmers and two county agriculture industry representatives visited four farms around Green Bay, Wis., in December to view their methane digesters first-hand.
"What we found out by visiting these farms is there is technology that is tried and true technology," Mr. Fultz said.
He said digesters can be installed on farms with anywhere from several hundred cows to 1,000 cows, but the cost per cow goes up on smaller operations. "There is definitely an economy of scale," he said.
The ballpark cost for a simple system is about $1,000 per cow on farms with around 500 cows and $500 per cow on farms with 3,000 cows, Mr. Fultz said.
In Wisconsin, the group met with Steve Dvorak, president of GHD Inc. Environmental Services. They viewed four of his patented digesters installed in the area over the last several years.
Mr. Dvorak's digesters are all underground and of concrete construction, Mr. Fultz said. They are flat on top with a concrete lid. Manure goes in one end and is pushed through the cells of the U-shaped container, coming out the other end in about 22 days.
The center wall contains heating coils, and the heat causes a circular pattern of movement for greater efficiency, Mr. Fultz said. The digester is sealed with spray insulation to prevent heat from escaping. A clearance of 18 inches at the top captures the rising gases.
At the last Wisconsin farm they visited, the group saw the inside of a digester. "It was neat to be able to see that," Mr. Fultz said.
At Holsum Dairy in Hilbert, Wis., there are 3,500 cows total with 2,900 in milk. The farm has operated for 3 1/2 years, and the digester has been up and running for 2 1/2 years, Mr. Fultz said.
Cows are milked three times per day, and fresh cows, those that recently calved, are milked four times per day. The typical dairy farm milks twice a day.
The farm's milk supply has an average somatic cell count of 130,000 using solids from the digester as bedding material for the cows, Mr. Fultz said. Pre-digester, they used rice hulls for bedding, and the SCC never dropped below 350,000.
According to the National Mastitis Council, the somatic cell count for "normal" milk is nearly always less than 200,000. Higher counts may be considered abnormal and indicate probable infection.
The manure solids at the end of the digestion process are 30 percent dry matter. Used for cattle bedding, the solids look like wet sawdust, dry quickly and do not stick to the cows that lie in it like sand or sawdust.
"Every cow we saw was very clean. We saw excellent stall utilization," Mr. Fultz said.
The farm sells solids to six other dairies for bedding and has seen a lot of benefit from using the liquids from the digestion process as irrigation for the fields, particularly in the form of increased alfalfa yields, Mr. Fultz said. That increase may be in part due to last year's drought cutting yields.
Holsum Dairy had a $475 per cow investment for their manure digestion system, Mr. Fultz said. The farm converts gas to electricity using two engines and produces double the energy they need for their own use. Benefits are in the form of electricity sales, savings in bedding and bedding sales.
Because other waste solids can be put into a digester, malt from a local company goes to the digester, and the farm is paid 1 cent per gallon tipping fee. The malt costs 6/10 of a cent to process, so they realize 4/10 of a cent in profit, Mr. Fultz said.
Maintenance on the digester adds up to about one-half to one hour per day. Another benefit is using the digester to compost dead calves. Calves disappear within a few days.
"You wouldn't want to fall into one of those things," Mr. Fultz said.
The second farm the group visited was Double S Dairy, milking 750 cows in Markesan, Wis. The digester was installed in the spring of 2002. The farm started with a Hess brand engine at the request of the power company, Mr. Fultz said. The engine did not work well, and the farm now has a Caterpillar engine.
Also visited was 600-cow Gordondale Farms in Nelsonville, Wis. The owners' Caterpillar engine is too small, and they burn off some gas, Mr. Fultz said. The farm sells solids from the digester for $20 per ton -- about double what other farms are selling it for -- due to high demand. All solids are transported in bulk and can be used as compost by area gardeners.
Quantum Dairy has 600 cows with plans to go to 1,600. The dairy is building an all-new facility, putting in a digester first, Mr. Fultz said. The owner is a third-generation master cheesemaker who bought land to protect from development. The vertically-integrated farm includes a dairy cheese plant that makes extra sharp cracker barrel cheese for Kraft.
Colby Ferguson of the Frederick County Office of Economic Development said two or three farmers in Frederick County may be considering digesters, but work must be done legislatively and financially.
"Our legislation, we're going to have to do some adjustments to that," Mr. Ferguson said. "We're thinking this also might be an opportunity for people who want to purchase renewable energy."
To help the farmers with funding for the digesters, Mr. Ferguson said a U.S. Department of Agriculture energy grant could be applied for as early as July.
Mr. Dvorak's GHD Inc. Environmental Services wrote 18 grants and received all 18 last year, Mr. Ferguson said. "We will probably use them to help write grants."
The USDA grant funds only 25 percent of the project cost, he said. Other grants or investors could make up the difference.
"There's a group of investors looking to invest in renewable energy for tax credits," Mr. Ferguson said. Farmers would repay them with monies received from sales of bedding, electricity, propane and possible tipping fees from area companies looking to get rid of their waste.
The farmers who went on the trip said digesters were definitely a possibility in Frederick County. "I came away pretty excited about the project," said Tuscarora dairy farmer Chuck Fry.
Although his farm of about 200 cows is too small for a digester to make much sense financially, turning manure into natural gas is a more feasible but very new option. The technology reduces the overall cost because an engine to turn gas into electricity is not needed. The engine is typically about one-third the cost of the system.
"It's a very new technology. We're not quite there yet. Give it about a year," he said.
Using natural gas is also viable on his farm because he could use it to heat his nearby turkey houses. "We run the turkeys on natural gas," he said.
Mr. Fry said methane digesters are a great alternative for farmers because they produce no odor and turn manure into usable bedding material. "It literally takes out all the smell and ends up smelling like corn silage," he said.
"I think in the right application, it's great," said Walkersville dairy farmer Jimmy Stup. "What I learned from the trip was I didn't feel it was right for our situation."
On the Stups' 900-cow dairy, they use sand for bedding and recycle water to wash the barns in a flush system. "The flush makes it difficult but not impossible."
He's also not sold on the idea of using recycled manure as bedding for cows. "Stan seems to think it would be great," he said.
"We built the system to handle the sand," Mr. Stup said.
Source: Knight Ridder/Tribune Business News