Presented by Evan H. DeLucia, Department of Plant Biology, University of Illinois
September 7, 2011
The ecological sustainability of biofuel crops is in large measure a land use issue; the ability of given landscape to retain carbon and nitrogen may be altered by displacing current patterns of land use or vegetation with different biofuel feedstocks. These changes can be positive or negative depending the specific changes in land use or vegetation type. In the US, both feed and bioenergy are produced from corn, despite the water and air pollution that are associated with its mass production. We used a process-based model to estimate the effects of replacing corn ethanol with alternative crops on both food and ecosystem services. If cellulosic feedstocks were planted on cropland that is currently used for ethanol production in the US, 82% more ethanol and 4% more grain for food could be produced, with a 16% reduction in nitrogen leaching and >450% reduction in greenhouse gas emissions. Adjusting for indirect land use change associated with displacing food and feed production with fuel production reduced the climate benefit of planting perennial feedstocks, but the change from a high input annual to a low input perennial crop still would transition the Midwest from a net source to a sink for greenhouse gases. Beyond the Midwest there is need to quantify the climate services of different ecosystem types, including the ability to retain greenhouse gases. We propose two new metrics, the greenhouse gas value, GHGV and the climate regulating value, CRV to quantify the climate services of ecosystems. These values provide important metrics for life cycle analyses of biofuel crops and also can be used to monetize the climate services of ecosystems. The judicious placement of biofuel crops with consideration of the land use and cover type they displace will greatly enhance their ecological sustainability.