The influence of catalysts on biofuel life cycle analysis (LCA)

Catalysts play an important role in biofuel production but are rarely included in biofuel life cycle analysis (LCA). In this work, we estimate the cradle-to-gate energy consumption and greenhouse gas (GHG) emissions of Pt/γ-Al₂O₃, CoMo/γ-Al₂O₃, and ZSM-5, catalysts that could be used in processes to convert biomass to biofuels. We also consider the potential impacts of catalyst recovery and recycling. Integrating the energy and environmental impacts of CoMo/γ-Al₂O₃ and ZSM-5 into an LCA of renewable gasoline produced via in-situ and ex-situ fast pyrolysis of a blended woody feedstock revealed that the ZSM-5, with cradle-to-gate GHG emissions of 7.7 kg CO₂e/kg, could influence net life-cycle GHG emissions of the renewable gasoline (1.7 gCO₂e/MJ for the in-situ process, 1.2 gCO₂e/MJ for the ex-situ process) by up to 14% depending on the loading rate. CoMo/γ-Al₂O₃ had a greater GHG intensity (9.6 kg CO₂e/kg) than ZSM-5, however, it contributed approximately only 1% to the life-cycle GHG emissions of the renewable gasoline because of the small amount of this catalyst needed per kg of biofuel produced. Given that catalysts can contribute significantly to biofuel life-cycle GHG emissions depending on the GHG intensity of their production and their consumption rates, biofuel LCAs should consider the potential influence of catalysts on LCA results.