Improving the Biofuels vs. Afforestation Debate
This project increases understanding of where and under what conditions, if any, the growth of biofuel feedstocks is preferable to afforestation, in terms of greenhouse gas balances. The scope is global, but we focus particularly on marginal and degraded land. Previous analyses addressing similar questions have used broad coarse classifications, ignoring much of the important variability in environmental factors (e.g. soil characteristics) and anthropogenic influences (e.g. past land uses, future management regimes). We explore this issue in much greater depth. First, we conduct a comprehensive literature review to compile data for refining previous estimates and to identify key gaps in knowledge. Second, we conduct quantitative analyses of afforestation and biofuel crop scenarios, with the goal of identifying the regions and soil conditions that are best suited for each option.
Currently, there is thought to be about 385-472 million hectares of abandoned agricultural land which could provide substantial greenhouse gas mitigation under carbon-positive management scenarios. The project goal was to identify the biophysical conditions where biofuels are a better option, from the perspective of GHG emissions mitigation, for these marginal lands than afforestation and vice versa. The first component of the project examined important sources of uncertainty in the carbon accounting literature on recovering forests. We determined that increased data collection on pre-restoration site quality, prior land use history, and management practices as well as increased methodological standardization could greatly reduce the current uncertainties in the literature. The second component of the project compared the GHG mitigation potential of several important forest recovery and biofuel production scenarios. Specifically, we compared the carbon sequestration potential of active and passive forest recovery systems to the carbon offset potential of several first and second-generation biofuels that would displace conventional petroleum products. We found contrary to current thinking that under many circumstances it appears that the two mitigation options are indistinguishable in their ability to sequester/offset carbon over a 30-year time frame, and in some cases, bioenergy production appears to provide considerably greater GHG offset potential.
Published in 2013
The Potential Impact of Second-Generation Biofuel Landscapes on at-Risk Species in the U.S., Samuel G. Evans, Lisa C. Kelley, Matthew D. Potts, Global Change Biology Bioenergy, doi: 10.1111/gcbb.12131, December 7, 2013.