Monday, November 5, 2007 - 1:20 PM
49-1
Environmental Sustainability of Biofuel Systems.
Kenneth G. Cassman, University of Nebraska, Nebraska Center for Energy Sciences Research, Lincoln, NE 68583-0724
The abrupt rise in petroleum prices since 2005 has led to a rapid expansion of biofuel production capacity from grain, sugar, and oilseed crops because it is now a profitable enterprise. Expansion is occurring in many of the world’s largest crop exporting countries: corn-ethanol in the USA , sugarcane-ethanol in Brazil , canola-biodiesel in Europe, and palm oil-biodiesel in Indonesia and Malaysia . As a result, global demand for these biofuel crops has increased substantially, which has caused crop prices to climb. Four challenges must be addressed to meet the increased demand for food, feed, and biofuel crops in a sustainable fashion: (1) acceleration in the rate of gain in crop yields well above the rate of yield gain since the Green Revolution began in the 1960s, (2) protection of soil and water quality on existing farmland, (3) avoiding expansion of cropping to marginal land or into natural ecosystems that are host to wildlife and biodiversity resources, and (4) contributing to a net reduction in greenhouse gas emissions (GHG) in the life-cycle production and use of biofuels as replacement for gasoline. Achieving these four objectives concomitantly will require a process of “ecological intensification” (EI) that includes average crop yield levels 85-90% of the genetic yield potential ceiling, improvements in soil quality, nitrogen fertilizer uptake efficiency of 70% or greater, integrated pest management, and +90% efficiency of water use in irrigated systems. While biotechnology and transgenic crop varieties represent a useful tool in the EI approach, they are by no means a silver bullet. Instead, the EI approach depends on optimization of all crop and soil management practices based on detailed understanding of agroecosystem structure and function with the explicit goal of achieving high yields while protecting environmental quality and contributing to a reduction in GHG emissions.