Indirect land use emissions in the life cycle of biofuels: regulations vs science

Abstract

Recent legislative mandates have been enacted at state and federal levels with the purpose of reducing life cycle greenhouse gas (GHG) emissions from transportation fuels. This legislation encourages the substitution of fossil fuels with ‘low‐carbon’ fuels. The burden is put on regulatory agencies to determine the GHG‐intensity of various fuels, and those agencies naturally look to science for guidance. Even though much progress has been made in determining the direct life cycle emissions from the production of biofuels, the science underpinning the estimation of potentially signifi cant emissions from indirect land use change (ILUC) is in its infancy. As legislation requires inclusion of ILUC emissions in the biofuel life cycle, regulators are in a quandary over accurate implementation. In this article, we review these circumstances and offer some suggestions for how to proceed with the science of indirect effects and regulation in the face of uncertain science. Besides investigating indirect deforestation and grassland conversion alone, a more comprehensive assessment of the total GHG emissions implications of substituting biofuels for petroleum needs to be completed before indirect effects can be accurately determined. This review fi nds that indirect emissions from livestock and military security are particularly important, and deserve further research. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd

Biofuels from crop residue can reduce soil carbon and increase CO2 emissions

“…20 Absolute changes in soil organic carbon (SOC) from corn residue removal have been estimated in LCA, 6 but few have estimated net changes in SOC and CO 2 emissions compared with no residue removal, 7,8,21,22 as required by consequential LCA. 23 Recent research suggests soil CO 2 emissions from residue removal could produce life cycle GHG emissions for cellulosic ethanol that exceed the mandated emissions reduction. 8 Incubation experiments with soil and corn residue showed that SOC is oxidized to CO 2 at 0.54-0.80 Mg C ha -1 per season when residues are completely removed.…”

“…On a relative basis, biofuels from crop residue yield a low amount of energy and oxidize a large C pool, producing high CO 2 emissions per unit energy, which is similar to the previously identified phenomenon for indirect land use change from biofuels. 23,35 Adding the five-year average emissions to other net production emissions (for example, biorefinery) of about 30 g CO 2 -equivalent per megajoule (g CO 2 e MJ -1 ) results in net GHG emissions for cellulosic ethanol at 100 g CO 2 e MJ -1 (Figure 3 and Supplementary Tables 7 and 8). The average value is 7% greater than gasoline (93.7 g CO 2 e MJ -1 ), 7 and 62 g CO 2 e MJ -1 above the 60% GHG reduction set by EISA.…”

Uncertainty Analysis of the Life-Cycle Greenhouse Gas Emissions and Energy Renewability of Biofuels

“…Rabl et al 2007;Guinée et al 2009;Luo et al 2009). One emerging but highly controversial issue in the GHG balance of biofuels is indirect land use change (iLUC) (Anex and Lifset, 2009;Liska and Perrin, 2009). In the approach proposed in this chapter iLUC is not considered, but a brief discussion is presented at the end of this section.…”

Can feedstock production for biofuels be sustainable in California?

“…The larger the difference between the energy used for feedstocks and that returned from the feedstock, the greater the net energy yield. High-energy yield per acre of cropland is a critical factor affecting sustainability (Liska and Perrin 2009). Many of the adverse greenhousegas effects of current biofuel production are attributed to the crop production component (Zah et al 2008).…”

“…Life-cycle analysis cannot anticipate future conditions and technical breakthroughs, so it is best used for comparison rather than setting absolute standards. Transparency and ease of use of life-cycle analysis models is needed to legitimize them as a basis for important public policy decisions (Liska and Perrin 2009).…”