Application of Hydroprocessing, Fermentation and Anaerobic Digestion in a Pyrolysis Refinery to Maximize Economic Value

This study investigates the economic and environmental benefits of integrating hydroprocessing, fermentation and anaerobic digestion into a pyrolysis refinery. Two scenarios were developed for upgrading and/or utilizing the primary products of pyrolysis (bio-oil, gas and char). The first (hydroprocessing) scenario hydroprocesses whole bio-oil into gasoline and diesel. The second (fractionation) scenario fractionates the bio-oil into sugars for fermentation to cellulosic ethanol and phenolic oil for esterification into phenyl esters (py diesel). Both scenarios use the gaseous product of pyrolysis for process heat in the plant and employ biochar to enhance anaerobic digestion of manure for production of methane for power generation.

The fast pyrolysis plant processes 2000 ton/day of corn stover while the anaerobic digester employs 430 ton/day of manure to generate power. The hydroprocessing scenario produces gasoline at a minimum fuel-selling price (MFSP) of $2.77 per gallons of gasoline while the fractionation scenario produces ethanol for $2.25 per gallon ($3.38 per GGE). Sensitivity analysis indicates that the MFSP for both scenarios is highly sensitive to the fixed capital cost. Fixed capital costs for the hydroprocessing and fractionation scenarios were estimated to be $643 million and $285 million, respectively. Fuel production rates for the hydroprocessing and fractionation scenarios are 60.5 and 7.7 million GGE per year, respectively. Life cycle greenhouse gas emissions were calculated as -7.6 and –108.9 gm CO_{2, eq} per MJ for the hydroprocessing and fractionation scenarios, respectively. LCA emissions are sensitive to by-product credits derived from biochar sequestration, phenolic oil utilization, and power generation. This study shows that both systems produce transportation fuels at competitive market prices with an additional reduction in atmospheric CO₂ levels in comparison to fossil fuel sources.