Second Generation Biofuels Reduce Emissions

By Pamela Porter

Dr. Mike Casler, USDA ARS Plant Breeder and CenUSA Co-PI has helped lead efforts to improve the yield of switchgrass by 40%. 

Could perennial grasses help the Midwest become a sink rather than a source of greenhouse gases? New research, published in the January 2016 issue of Nature Energy by scientists at the Universities of Illinois, Georgia, Colorado State, and Idaho, further validated the CenUSA Bioenegy vision. They found that relying on perennial grasses grown on marginal lands to meet the RFS could reduce greenhouse gases 7 to 12 percent while having a negligible impact on food crop production. The authors have called the study, the most comprehensive to date.

 “Our results were staggering,” said Evan Delucia, Plant Biology Professor at the University of Illinois and study co-author. Converting 40 percent of the corn grown for ethanol production to perennial grasses (miscanthus and switchgrass), “changed the entire Midwest from a net source of greenhouse gas emissions to the atmosphere to a net sink. The grasses require less fertilizer, which is a source of nitrous oxide, and they store more carbon in the ground than corn.”

The US Renewable Fuel Standard (RFS) sets targets for the production of biofuels and has come under debate as feedstocks differ widely in their costs, yields, inputs and GHG emissions. Compared to corn, perennial grasses have generally been shown to have lower GHG emissions because they require fewer fertilizer inputs, are not tilled annually and sequester carbon and build organic matter in the soil. In addition, perennial grasses have been shown to reduce soil erosion and nutrient runoff by as much as 90% over annual crops and offer important conservation and wildlife benefits.

This study, “Impacts of a 32 Billion Gallon Bioenergy Landscape on Land and Fossil-Fuel Use in the U.S.“ attempted to improve on previous studies by combining ecosystem modeling with economic modeling to test different biofuel scenarios including a biofuel production tax credit. Researchers found that replacing 40% of annual crops grown on marginal land with perennial bioenergy crops could double the reduction in greenhouse gas reductions compared to no a no biofuel scenario.

The paper can be found here:
http://www.nature.com/articles/nenergy20155