EU sustainability criteria for biofuels: uncertainties in GHG emissions from cultivation

Background: Cultivation of raw material represents a large proportion of biofuels´ greenhouse gas (GHG) emissions. The EU renewable energy directive 2009/28/EC specifies a GHG emission default value for cultivation of biofuel raw material (23 g CO2e/MJ ethanol for wheat). The aim of this study was to quantify the uncertainty in GHG emissions for wheat cultivation in Sweden, considering uncertainty and variability in data at farm level. Results: Two levels of data collection at farm level were analyzed; simple (only yield and amount of N) and advanced (also including amounts and types of energy). The 2.5-97.5 percentile uncertainty for Swedish winter wheat was 20-27 g CO2e/MJ, which can be considered large in the context of the Directive’s threshold of 23 g with two significant digits. Conclusions: It is concluded that quantifying GHG emissions in order to regulate biofuels is a difficult task and especially emissions from cultivation since these are biological systems with large variability.