Manure digestion as fuel getting a second look in Pennsylvania

University Park, Pa. -- It's funny how old, neglected ideas become hot, new ones again when energy prices spike.

Thirty years ago, researchers in Penn State's College of Agricultural Sciences operated an experimental manure digester on the University Park Campus in Centre County. In the midst of an energy crisis brought on by uncertainty about the flow of Middle Eastern oil, the pilot project was thought to have considerable promise for demonstrating how biogas could be produced from animal manures on Pennsylvania farms. This low-grade "natural gas" could then be used to generate electricity or replace other energy used on farms for needs such as water or space heating.

One can find the remains of the digester's foundation, crumbling and forgotten behind the University's dairy barns, across the road from Beaver Stadium. The project did have an impact -- by the end of the decade, using technology proven by the Penn State digester, Pennsylvania had four manure digesters up and running. They remain today among the longest continuously operating on-farm digesters in the country.

"But interest in anaerobic digesters producing biogas and generating electricity on farms from methane never really caught on," said Bob Graves, professor of agricultural engineering. "It never made economic sense for most farms because once energy supplies stabilized, energy prices were still relatively low.

"Because the old digester was a research facility and not built for continuous extended operation, it was shut down and dismantled," he added. "Penn State was one of the first land-grant institutions to respond to the energy crisis of the '70s and demonstrate how anaerobic digesters could transform animal manure into an energy source, but the economics of manure digesters didn't favor the technology."

A lot has changed since the 1970s. Oil is more than $70 a barrel, gas is around $3 a gallon, natural gas prices have gone through the roof -- and ideas that didn't make sense back then now suddenly do. "But regardless of the price of oil, using a renewable resource such as manure to create so-called 'green' energy is a good idea," Graves said.

Penn State's College of Agricultural Sciences recently received U.S. Department of Agriculture funding for research that will address key profitability and performance challenges with establishing and operating on-farm digesters and developing standards for digester design. Tom Richard, associate professor of agricultural and biological engineering, believes the potential for Pennsylvania farmers using digesters is enormous.

"Anaerobic digesters can provide significant environmental benefits on dairy farms, while producing renewable energy for on-farm use or sale to the utility grid," he said. "State and federal agencies have promoted digesters for more than 30 years, demonstrating dramatic reductions in odor and greenhouse gas emissions, as well as more predictable nutrient availability.

"Although many on-farm digesters have been built, few have achieved long-term success," Richard added. "Most failures have resulted from overly optimistic economic projections, in some cases due to naive maintenance expectations. Several persistent performance challenges will be addressed in the research."

Richard cites the discovery of "methanogenic" microorganisms recently isolated from cool, acidic bogs in central Pennsylvania as a development that will result in better digesters. "Incorporating those microorganisms into the digestion process should improve the resilience of digesters to operational variability," he said. "We will be developing a standardized package of hardware and software for remote monitoring and process control. We also hope to establish a new business model involving third-party consultants to provide professional services and expertise, much like the nutritionists, veterinarians and crop consultants that dairy producers contract with today."

Richard also plans to develop standardized designs for complete digester systems, so that each farm digester does not have to be a completely custom design. "The cost savings associated with standardization, third-party monitoring, less maintenance and increased reliability should result in increased numbers of successful installations and eventually make digesters attractive to many more livestock farms," he said.

Penn State scientists also are keeping tabs on manure digesters built to prove new technologies. One at Pine Hurst Acres Farm -- a 4,400-hog operation owned by Stanley Crone in Northumberland County -- is using a new design to collect manure and pump it to the digester. Senior extension educator Robb Meinen is monitoring the operation.

"One of our main goals is animal health, and we are trying to make sure that taking manure out from below the barn floor, digesting it and then returning it to beneath the floor is not negatively affecting the animals," he said. "We are measuring the levels of hydrogen sulfide, ammonia, methane and oxygen. Our overall analysis of the operation will consider economic, management and design aspects. We hope to provide pieces to the puzzle that lead to an affordable farm-level digestion blueprint."

Society is looking to agriculture for solutions to energy problems, Meinen believes. "Elected officials are not very eager to tour pig farms, but they are eager to see solutions for energy and odor issues," he said. "In a world faced with rising fuel costs, global warming and nutrient-management pressures, we might be able to help facilitate a change. Pennsylvania has enacted an Alternative Energy Portfolio that requires electric producers to use alternatives to fossil fuels to produce 18 percent of their electricity by the year 2020, so even the energy companies are paying attention."