Set-Asides Can Be Better Climate Investment than Corn-Ethanol

PIÑEIRO, GERVASIO; JOBBAGY, E.G.; BAKER, J; MURRAY, B; JACKSON, R.B.

Washington, DC, USA

Congreso; Ecological society of America Conference on the ecological dimensions of Biofuels; 2008

Ecological society of America

Net carbon emissions from biofuel production depend on land-use history and whether carbon is lost from soil organic matter.  We compared the effectiveness and economic value of corn- and cellulosic-ethanol production with conservation approaches, such as the Conservation Reserve Program (CRP), for reducing net greenhouse gas emissions. We assembled 142 unique comparisons of soil organic carbon (SOC) accretion in set-aside programs to determine rates of soil carbon storage.  Based on our comprehensive dataset, the average SOC accretion in set-aside programs was 570± 185 kg C ha-1 yr-1 (2.088  ± 0.679 tons of CO2 eq.ha-1.yr-1) after crop production ended. We used these data to refine estimates of net GHG emissions through time for different starting points of corn- and cellulosic-ethanol production, including existing croplands, CRP lands, and grasslands.  We then determined the net present value (NPV) for each mitigation strategy, a summary measure of current economic value ($.ha-1) in terms of GHG emissions.  After including estimates of SOC change, our analysis shows that maintaining lands in set-aside programs reduces net GHG emissions more than corn-ethanol production for at least four decades. Perhaps most surprisingly, converting land under long-term cultivation to CRP has a more positive GHG balance than corn-ethanol production for 42 (±20) years. Additionally, corn-ethanol production typically had a lower net present value (NPV) for GHG savings than set-aside programs, as well as a higher cost to the U.S. government. Cellulosic-ethanol production, once commercially available, should provide the most efficient tool for GHG reduction of any scenario we examined.