The Science Insider blog last week hosted an interesting debate between Tim Searchinger, Princeton visiting scholar, and John Sheehan, of the Institute on the Environment at the University of Minnesota, regarding the recent policy proposal in the pages of Science by Searchinger et al. to “fix” the carbon accounting of biomass for bioenergy and biofuels in U.S. legislation and the successor to the Kyoto protocol, by giving credit only to biomass that can be managed in such a way as to sequester additional atmospheric carbon in the soil. As Searchinger puts it in the recent debate, “bioenergy only reduces greenhouse gases if it results from additional plant growth or in some other way uses carbon that would not otherwise be stored.”
To be sure, use of bioenergy can only reduce the overall level of greenhouse gases in the atmosphere by sequestering carbon in the soil (in root systems). And yes, individual biofuel or bioenergy producers could use only new biomass that has recently pulled carbon from the atmosphere (although other environmentalists may differ on that) or biomass that would otherwise be left to decay and emit the stored carbon anyway. The question then is whether there is enough of this type of biomass to meet energy needs.
But that is not the point of the current Kyoto protocol or of U.S. cap-and-trade legislation. Their shared goal is to reduce overall GHG emissions, over time, ideally lowering the cap until emissions reach equilibrium.
Searchinger cites recent modeling studies to say that not employing his fix to global carbon accounting “would lead to the loss of most of the world’s natural forest because clearing those forests for bioenergy becomes one of the cost-effective means of complying with laws to reduce greenhouse gas emissions.” However, the fossil fuel industries are certain to receive allowances under the U.S. legislation. Employing a carbon accounting model that treats biomass as equivalent to fossil fuel would definitely make continued reliance on fossil fuel the cost-effective alternative.
Another interesting response to the Searchinger et al article comes from Geoff Styles of the Energy Collective, who extends the carbon accounting argument to electric vehicles. All alternative energy sources can be opened up to particular scrutiny. What is needed is a truly accurate and balanced accounting of fossil fuel use to compare these arguments.
The only other political option would be to drastically cut use of all energy. Models do project that the current worldwide economic recession has brought about a reduction in climate emissions by cutting energy use.
Searchinger does note that biomass and biofuels have the potential to balance greenhouse gas emissions – depending on land management. A better question here is whether his models can show that fossil fuel use also has the potential to balance greenhouse gas emissions with proper land management.