In 2007, farmer Bryan Sievers began researching an idea for a large cattle feedlot and came up with a plan that makes the entire enterprise “green.”
Along with his wife, Lisa; son, Jon; and his father, Glenn, the family came up with a way to turn the feedlot waste into electricity. In this instance, it is the cattle waste they are using.
Sievers uses the manure from the cows to feed into a biomass digester, the methane from which is used generate electricity for the feedlot. What is left over from the production of electricity is fertilizer for the corn and soybean crops.
From the idea was born AgriReNew, a joint venture between Sievers Family Farms, Sievers Renewable Energy and Davidson Renewable Energy, an outside investor.
Just this year, the American Biogas Council presented the inaugural Biogas Project of the Year award to the Stockton, Iowa-based company for its biomass digester, which uses the manure to generate methane that drives an engine that turns the turbine. Alliant Energy has an option to buy the unused electricity.
As AgriReNew manager, Bryan Sievers said the digester and its accompanying engine and turbine became fully operational Dec. 1.
“This is a completely sustainable closed-loop concept,” Sievers said. “We have two 970,000-gallon tanks into which we put 30,000-35,000 gallons of manure plus ground-up corn cobs that we use as bedding for the cattle.”
The manure and corn cobs are in the digester tanks for 40 days, producing methane to generate the electricity for the feed lot, which has two cattle barns that will hold 1,222 head of cattle each, he said.
The investment for the project, including the digester, the buildings and all the construction, totaled $7 million, which has been backed by Caterpillar Financial. Organic Waste Systems, headquartered in Ghent, Belgium, was the consultant on the project.
The system means, Sievers said, that “there is a small amount of odor, but we’ve eliminated 99 percent of the pathogens associated with the manure.”
What is left after the 40-day digesting process is some liquid fertilizer and bio-solids, all of which is rich in phosphorous, potassium and nitrogen. Those are the exact nutrients farm soil needs to grow corn and soybean crops. These nutrients are spread on the fields.
“We don’t buy our potassium and phosphorous anymore,” Sievers said. He still supplements the nitrogen, however.
“There’s really no waste here,” he said.
The digester is producing about 650 kilowatts of electricity an hour, which could power about 450 homes, he said. It is running at about two-thirds of its 1-megawatt capacity.
“By creating a sustainable operation where essentially nothing goes to waste, each enterprise will benefit from the waste streams created by the other enterprises,” Sievers said.
“For example, the crops we raise provide resources to the operation of our commercial beef cattle feedlot. The crop residues also provide resources to the feedlot and the digester. The manure from the feedlot provides resources to the digester. The liquid fertilizer and bio-solids produced from the digester provide resources to the crop operation, and the methane that's captured by the digester reduces our carbon footprint and is used to generate electricity, which helps generate revenue to cover capital investment, operating costs and a return on investment.”
Justin Foss, spokesman for Alliant Energy, visited the Sievers’ operation to highlight the digester and raise awareness of the many places Alliant Energy buys the electricity it uses for its customers.
“This year, there are 520 Iowa Alliant Energy customers producing renewable energy on their site,” Foss said. “That’s a huge number, considering the work it takes and the capital it takes. It’s about a 30 percent increase over the last two years.”
Often, customers do not understand the many places from which Alliant purchases energy to power their needs, he said.
“We want to raise awareness of our diverse mix of energy generation, from natural gas, to coal, to nuclear to wind and solar,” Foss said. “We even purchase energy from hydro-electric dams in Iowa. They’re small, but they’re a part of our diverse network.”
Alliant even purchases energy from digesters, such as the only one in Iowa — on the Sievers’ farm, but they are more plentiful in Wisconsin.
Sievers said the feedlot would have been feasible on its own merits without the digester operation.
“Each of our enterprises has to stand on its own merits,” he said of AgriReNew and Sievers Family Farms. “However, the goal of our farming operation is to maximize the value of its resources, and hopefully, generate a profit.”