A cross-border team of researchers refute arguments that carbon debt, opportunity cost and indirect land-use change prevent greenhouse gas mitigation by biofuels. Credit: Oak Ridge National Lab
That biofuels can contribute to a cleaner global energy mix is widely accepted, but the net benefits of bioenergy in terms of mitigating greenhouse gases (GHG) are moot. Some argue, for example, that biofuels are not sustainable because the conversion of non-agricultural land to grow energy crops could lead to a significant initial decrease in carbon storage, creating what is known as a "biofuel carbon debt".
A study by a cross-border group of researchers published in Proceedings of the National Academy of Sciences (PNAS) could help refute this argument.
The study showed that the GHG mitigation potential of switchgrass cultivation for cellulosic ethanol production in the US was comparable on a per-hectare basis to that of reforestation and several times greater than that of grassland restoration. Switchgrass (Panicum virgatum) is a widely grown North American native grass proposed as biomass for the biobased economy.
More advanced technology and integration of carbon capture and storage (CCS) could further increase the per-hectare mitigation potential of bioenergy systems by a factor of six, according to the study, which was supported by São Paulo Research Foundation—FAPESP via a project led by John J. Sheehan.
Sheehan is affiliated with the University of Minnesota in the US and is currently a visiting fellow at the University of Campinas's School of Agricultural Engineering (FEAGRI-UNICAMP) in the state of São Paulo, Brazil, under the aegis of the (São Paulo Excellence Chair (SPEC).
Co-lead author of the study, Lee R. Lynd, a professor at Dartmouth College in Hanover, New Hampshire (USA), began a project in February at UNICAMP's Center for Molecular Biology and Genetic Engineering (CBMEG), with funding from FAPESP under the SPEC program.
"The study highlights in detail the factors and strategies that are important to the implementation of biofuel production in a way that helps stabilize the climate," Lynd told.
According to the authors, critics of bioenergy question whether feedstock crops can be sustainably sourced without causing self-defeating reductions in ecosystem carbon…