"The old digester was a research facility not built for continuous extended operation, so it was shut down and dismantled,” he adds. “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 didn’t favor the technology.”

A lot has changed since the mid- 1970s. The price of oil spiked at more than $70 a barrel recently before falling back some, and at the same time natural gas prices went through the roof before sliding a little—and as a result, a lot of ideas that didn’t make sense before are getting a second look. “But regardless of the price of oil, using a renewable resource such as manure to create green energy is a good idea,” Graves says. “And while manure digestion doesn’t decrease the amount of manure farmers have to dispose of, it does reduce odor and can represent a savings in energy.

Agricultural engineer Robert Graves marks the site of the college's old experimental manure digester, which operate in the 1970s.

“While we obviously have a lot at stake in helping farmers to handle manure, our interest in manure digesters is twofold,” Graves adds. “Part of it is odor control and the second is energy. Pennsylvania has a large number of private and public electricity suppliers, and that has added to the challenge of accommodating small, distributed electricity generation from on-farm biogas production. We need to develop economically fair policies that accommodate interconnection with the power grid and provide for worker and public safety and reliable power quality.”

The college recently received funding from the U.S. Department of Agriculture for research that is addressing key profitability and performance challenges in establishing and operating on-farm digesters and developing standards for digester design. Graves 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 and sale to the utility grid,” he says. “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.

“But, although many on-farm digesters have been built, few have achieved long-term success,” Tom Richard notes. “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. Current digesters are very sensitive to low pH and are frequently upset by excess acid production, especially at ambient temperatures below 90°F. Even when things are operating well, heating digesters and buffering pH can be expensive.”

Richard cites the discovery of “methanogenic” microorganisms Penn State scientists recently isolated from cool, acidic bogs in north-central Pennsylvania as a development that will enhance digester operation. “Incorporating these microorganisms into the digestion process should improve the resilience of digesters to operational variability,” he says. “We hope to reduce the need for more active maintenance, and we will be developing a standardized package of hardware and software for remote monitoring and process control by third-party consultants— a new business model that will work in much the same way that many dairies now contract with nutritionists, veterinarians, and crop consultants.

“Finally, we plan to develop standardized designs for complete digester systems, so that farm digesters each don’t have to be a completely custom design,” Richard adds. “The cost savings associated with standardization, third-party monitoring, less maintenance, and increased reliability should result in a larger number of successful installations and eventually make digestors attractive to many more livestock farms.”

At this point, the future of bioenergy is not clear—it is difficult to predict which technologies and “crops” will triumph and economically provide the most energy to replace fossil fuels. But one thing is obvious—the process Rudolph Diesel set in motion with biofuels a century ago won’t be stopped, and Penn State’s College of Agricultural Sciences will play a role in how it develops. In the Northeast at least, the path to going greener may be paved in blue and white.

Faculty and staff referenced in this article are Thomas Richard, associate professor of agricultural and biological engineering; Gregory Roth, professor of agronomy; Charles Ray, assistant professor of wood products operations; John Carlson, associate professor of molecular genetics and director of the Schatz Center for Tree Molecular Genetics; Jeffrey Catchmark, assistant professor of engineering science and mechanics in the College of Engineering; Nicole Brown, assistant professor of wood chemistry; Mark Guiltinan, professor of plant molecular biology; and Robert Graves, professor of agricultural engineering. Paul Adler is a research agronomist with the U.S. Department of Agriculture’s Pasture Systems and Watershed Management Research Unit, based at Penn State’s University Park campus.