Carbon Footprint Analysis of Gasoline and Diesel from Forest Residues and Algae using Integrated Hydropyrolysis and Hydroconversion Plus Fischer–Tropsch (IH² Plus cool GTL)

Abstract

Life cycle analysis was conducted with a focus on greenhouse gas (GHG) emissions of renewable gasoline and diesel produced by the integrated hydropyrolysis and hydroconversion (IH²) and the new IH² plus Fischer–Tropsch (IH² Plus cool GTL) processes. This new process has a primary objective of increasing the yield of biofuel relative to original IH² process (increase of 26% to 38% wt) by processing the C1–C3 gas co-products through an integrated Fischer–Tropsch unit to produce liquid-range hydrocarbon biofuel. For both biofuel processes, woody biomass residues (forest logging and saw mills) and algae were investigated as feedstocks. The effect of the electricity generation mix of different states in the U.S. was also examined for algae cultivation. For woody residues as feedstock, life cycle GHG emission savings of about 86.8% and 63.3% were calculated for the IH² and optimized-IH² Plus cool GTL hydrocarbon biofuel, respectively, relative to fossil-derived fuel. For algae as feedstock, emission increases of about 140% and 103% were calculated for the IH² and optimized-IH² Plus cool GTL, respectively, relative to fossil-derived fuel. The electricity grid mix of the biorefinery location significantly impacts the GHG emissions of the processes for algae feedstock. GHG savings of about 42% can be potentially achieved if the plant was located in an area with a low GHG intensity grid. This study has shown that a significant biofuel yield boost can be achieved while retaining high GHG savings by using IH² Plus cool GTL for a woody feedstock