President Barack Obama wants U.S. scientists to pursue an “all-of-the-above” strategy in developing new sources of domestic energy.

Agricultural Research Service agronomist Paul Adler is providing complete cost-benefit breakdowns for using switchgrass pellets instead of fuel oil to heat homes and businesses in the Northeast.

“There have been a lot of studies on bioenergy potential,” says Adler, who works at the ARS Pasture Systems and Watershed Management Research Unit in University Park, Pennsylvania. “Most of them are focusing on transportation, but we still need a viable, commercial, biobased fuel substitute for petroleum.

“In the meantime, our studies suggest that we already have opportunities to use homegrown feedstocks for producing heat, and that we can save money, reduce petroleum use, and cut greenhouse gas.”

Adler and others conducted a life-cycle assessment comparing costs of energy generation from coal, natural gas, fuel oil, and switchgrass in the form of energy-dense cubes, briquettes, and pellets. His research partners included ARS technician Fred McNeal, Pennsylvania State University graduate student Tom Wilson, Wilson’s advisor David Abler, and Drexel University assistant professor Sabrina Spatari.

The researchers calculated the economic outlays associated with switchgrass production throughout the supply chain and the amounts of greenhouse gases — carbon dioxide, nitrous oxide, and methane — emitted during switchgrass production, densification, and conversion to heat and power. This included the first life-cycle inventory of switchgrass seed production and the greenhouse gas emissions associated with it, which the team developed using real-world information from a Pennsylvania producer.

The analysis indicated that 192 pounds of “carbon dioxide equivalent,” or CO2e, were emitted for every ton of switchgrass dry matter that was grown, harvested, and delivered to densification plants for processing into pellets. CO2e is a measurement used to compare the emissions from various greenhouse gases based on their global-warming potential.

More than 54 percent of these emissions were from nitrous oxide resulting from nitrogen fertilizer application, while farm equipment operation also produced substantial levels of greenhouse gases.

Processing each ton of dry matter into pellets generated another 287 pounds of CO2e; 78 percent of these emissions stemmed from grinding and pelletizing processes, with the remainder coming from the drum dryer.

With these findings in hand, the researchers calculated that using switchgrass pellets instead of petroleum fuel oil to generate one gigajoule of heat in residences would reduce greenhouse gas emissions by 146 pounds of CO2e. Using switchgrass pellets instead of natural gas to produce one gigajoule of heat in residences would reduce greenhouse gas emissions by 158 pounds of CO2e.