Life-Cycle Assessment of Pyrolysis Bio-Oil Production

As part of the Consortium for Research on Renewable Industrial Materials' Phase I life-cycle assessments of biofuels, life-cycle inventory burdens from the production of bio-oil were developed and compared with measures for residual fuel oil. Bio-oil feedstock was produced using whole southern pine (Pinus taeda) trees, chipped, and converted into bio-oil by fast pyrolysis. Input parameters and mass and energy balances were derived with Aspen. Mass and energy balances were input to SimaPro to determine the environmental performance of bio-oil compared with residual fuel oil as a heating fuel. Equivalent functional units of 1 MJ were used for demonstrating environmental preference in impact categories, such as fossil fuel use and global warming potential. Results showed near carbon neutrality of the bio-oil. Substituting bio-oil for residual fuel oil, based on the relative carbon emissions of the two fuels, estimated a reduction in CO2 emissions by 0.075 kg CO2 per MJ of fuel combustion or a 70 percent reduction in emission over residual fuel oil. The bio-oil production life-cycle stage consumed 92 percent of the total cradle-to-grave energy requirements, while feedstock collection, preparation, and transportation consumed 4 percent each. This model provides a framework to better understand the major factors affecting greenhouse gas emissions related to bio-oil production and conversion to boiler fuel during fast pyrolysis.