Modeling potential freshwater ecotoxicity impacts due to pesticide use in biofuel feedstock production: the cases of maize, rapeseed, salix, soybean, sugar cane, and wheat.

The inclusion of ecotoxicity impacts of pesticides in environmental assessments of biobased products has long been hampered by methodological challenges. We expanded the pesticide database and the regional coverage of the pesticide emission model PestLCI v.2.0, combined it with the impact assessment model USEtox, and assessed potential freshwater ecotoxicity impacts (PFEIs) of pesticide use in selected biofuel feedstock production cases, namely: maize (Iowa, US, two cases), rapeseed (Schleswig-Holstein, Germany), Salix (South Central Sweden), soybean (Mato Grosso, Brazil, two cases), sugar cane (São Paulo, Brazil), and wheat (Schleswig-Holstein, Germany). We found that PFEIs caused by pesticide use in feedstock production varied greatly, up to 3 orders of magnitude. Salix has the lowest PFEI per unit of energy output and per unit of cultivated area. Impacts per biofuel unit were 30, 750, and 1000 times greater, respectively, for the sugar cane, wheat and rapeseed cases than for Salix. For maize genetically engineered (GE) to resist glyphosate herbicides and to produce its own insecticidal toxin, maize GE to resist glyphosate, soybeans GE to resist glyphosate and conventional soybeans, the impacts were 110, 270, 305, and 310 times greater than for Salix, respectively. The significance of field and site-specific conditions are discussed, as well as options for reducing negative impacts in biofuel feedstock production.