Biofuels: a New Methodology to Estimate GHG Emissions Due to Global Land Use Change

by Roland Hiederer, Fabien Ramos, et al. (European Commission Joint Research Centre) This study implements a new methodology developed by the JRC IES and IE for estimating changes in greenhouse gas (GHG) emissions from soil and above- and below-ground biomass resulting from global land use changes caused by the production of biofuels. The methodology is based on the Tier 1 approach as developed under the IPCC 2006 Guidelines for National Greenhouse Gas Inventories. Under this approach GHG emissions are estimated from comparing the pre-land use change carbon stocks with the carbon stocks after the conversion.

The study incorporates the output from global economic models on land use change as input data to calculate the related GHG emissions. Used are cropland demands from the general equilibrium model MIRAGE (run by IFPRI) and from the partial equilibrium model AGLINK-COSIMO (run by JRC-IPTS).

A novelty of the study is the development of a harmonized spatial data set and advanced analysis methods for all aspects of estimating GHG emissions. In the spatial allocation process cropland demands from the output of the economic models are processed for a global raster layer with approx. 10 km grid spacing. The outcome of the spatial allocation process allows computing changes in land use, which are the related changes in soil carbon stock and N2O emissions and the changes in carbon in the affected biomass.

The output from IFPRI-MIRAGE analysis was available to the study for two scenarios: one assuming conditions of “Business as Usual” (BAU) and one assuming “Free Trade” conditions (FT). The total cropland area attributed to ILUC for 2020 over the reference area for that year is 8,209 km2 (BAU) and 9,759 km2 (FT). Most of the additional cropland is assigned to Brazil and the Commonwealth of Independent States regions, while changes in cropland attributed to ILUC in Europe small. For the BAU scenario total GHG emissions from ILUC are estimated at 201 Mt CO2eq (BAU) and 248 Mt CO2eq (FT) over a period of 20 years. For the JRC-IPTS AGLINK-COSIMO simulation, the area change due to biofuels policy is 52,372 km2. Major cropland extension occurs in EU27 followed by Brazil, Argentina and the region of other Asian countries. Estimated total GHG emissions are 1,092 Mt CO2eq.

For all the scenarios the major contribution (approx. 80%) to total GHG emissions results from the removal of above- and belowground biomass. Changes in soil carbon stock contribute with 15 to 20%, whereas N2O emissions related to loss in soil carbon stocks have only a small share (2 - 3%).

Compared to the emissions figures published by IFPRI the emissions estimated from this study are about 4 times higher. The differences between the output from the two models, but also from this study and the IFPRI assessment, are attributed to different assumptions on the share of crops for bioethanol or biodiesel production between the models and the proportion of forest and shrubland converted to allow the additional cropland demand. Download study READ MORE