Recent estimates of indirect land use change impacts associated with biofuel expansion have used forward-casting models to predict the effects of changes in feedstock use upon agricultural commodity markets and land use decisions. The predictive reliability of such models is highly questionable and their application provides a limited basis for practical solutions either by the biofuel industry or by policy makers.
We propose a three step approach based upon actual land use change data, leading to progressive definition and attribution of responsibility for LUC over time:
Step 1: Estimation of LUC emissions associated with marginal changes in output of commercial agricultural crops based on a share of actual LUC emissions (using standard allocation methods)
Step 2: Separation of direct and indirect emissions, such that total LUC emissions = directly attributed emissions + indirect emissions (to avoid double-counting)
Step 3: Progressive attribution and acceptance of responsibility towards direct effects by each sector and producer, thus reducing the residual pool of indirect emissions
Using this allocation based approach, we provide initial estimates of LUC emissions attributable to biofuels (and to commercial agriculture in general). Marginal LUC emissions for various biofuels for the period 2000 to 2005 ranged from 10 to 45 g CO2 / MJ. Whereas, mean LUC emissions for the same biofuels for this period ranged from 0.9 to 4 g CO2 / MJ. We expect that the application of environmental safeguards to protect high carbon ecosystems, as parts of Steps 2 and 3 will enable these figures to be reduced over time. Policy makers should note the difference between mean and marginal figures and avoid confusion in reporting frameworks. Marginal figures, which reflect the likely impacts of new output from commercial agriculture in the absence of safeguards, should be used to inform policy decisions but product reporting should use mean impacts to accurately describe the average impact of each unit of product.