Researchers in North Carolina have created a better way to convert hog manure to energy, but producers in the Midwest are unlikely to rush to implement it.

Their reservations are based on a combination of factors, but center primarily on the upfront costs involved.

With low energy costs and a price tag that can top $1 million, anaerobic digester systems, which capture methane to produce electricity, simply don’t justify the investment, producers say.

That’s particularly true as grant support that has been used to help offset the costs of such projects evaporates, they say.

The U.S. Department of Agriculture announced earlier this month that their Rural Energy for America Program, a large source of funding for farm-based renewable energy projects, was allotted $25.4 million this year, down from $75 million in 2011.

“These are expensive to put in, and if we already have cheap electricity rates the cost to make our own power still isn’t cost effective without getting grant dollars to install these systems,” said Bill Crawford, the president of the Minnesota Pork Board.

Anaerobic digesters have been around for more than a decade, and can be found across the Midwest. In agricultural applications, they are primarily located at dairy farms that have larger concentrations of animals and a better economy of scale.

Officials in Iowa, which is by far the largest pork-producing state in the U.S., as well as in Minnesota and Wisconsin said they knew of no hog farms using such systems. There is at least one in operation in Nebraska.

The North Carolina system was built, at a hog farm with 8,600 hogs that produces 400,000 gallons of waste a week, after the state incorporated hog manure into their renewable energy standard.

Renewable portfolio standards in Minnesota, Wisconsin, Illinois count anaerobic digesters as sources of renewable energy, but do not require their use.

Developed with the backing of Duke University and Google Inc., which are purchasing carbon offsets from the project, the system includes the same basic features as traditional anaerobic digesters.

But it is set apart from previous designs because it also includes a basin that removes ammonia and other pollutants from leftover liquid so that it can be used for irrigation and on the farm.

Builders say it also reduces the level of nitrogen, phosphorous and other pollutants in the manure, creating a usable fertilizer. Previously, farmers with unusable manure put it into lagoons that could degrade water and air quality.

“I think the important thing to note is that the potential exists to harvest the energy value of the waste to facilitate further treatment of the waste and assist the farmer with his operations as a whole,” said Gus Simmons, the director of engineering at Cavanaugh & Associates, which designed and built the system.

The North Carolina system is capable of creating around 500 megawatt-hours of electricity a year. Officials say that’s enough to power around 35 homes, although the electricity is being used entirely on the farm now.

It cost $1.2 million to build and, although a cost analysis is ongoing, Simmons said it has proven to be more efficient than expected, and that it will likely pay for itself within a decade.

Future systems could presumably cost less because the price tag included research and development costs that future developers won’t have to absorb. The designs are also being made available to the public, and the system can be built using equipment that is readily available to farmers.

“We tried to ensure that this system could be operated easily by a farmer using conventional style farming equipment, and were very deliberate in our design approach to create a system that was as close to conventional farming processes as possible,” Simmons said.

Still, despite finding promising results in the year the North Carolina system has been up, Simmons acknowledged variables between farms around the country – including climate, scale and energy costs – make each situation unique.

“Every farm is different, so it’s not as though you can replicate the exact dimensions and capacity and expect the same result,” he said.  

Photo by dannyakright via Creative Commons