Application of Hydroprocessing, Fermentation, and Anaerobic Digestion in a Carbon-Negative Pyrolysis Refinery

Abstract

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 bio-oil into sugars for fermentation to cellulosic ethanol and residual phenolic oil as the primary product. Both scenarios use the gaseous product of pyrolysis for process heat in the plant and employ biochar to enhance anaerobic digestion of manure 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 and phenolic oils (diesel) as a transportation fuel for $1.2 per gallon ($1.41 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 and $288 million, respectively. Fuel production rates for the hydroprocessing and fractionation scenarios are 60.5 and 16 million GGE per year, respectively. Life cycle greenhouse gas emissions were calculated as −9.6 and −16.6 g CO2,eq per MJ for the hydroprocessing and fractionation scenarios, respectively. LCA emissions are sensitive to byproduct credits derived from biochar sequestration and power generation. This study shows that both systems produce transportation fuels at competitive market prices with an additional reduction in atmospheric CO2 levels compared to fossil fuel sources.

Enhancing Biochar as Scaffolding for Slow Release of Nitrogen Fertilizer

“…Techno-economic analysis at Iowa State University of fast pyrolysis biorefineries suggests a market price for biochar ranging between $50 and $100/metric ton. − Urea price ranges between $377 and $407/metric ton or between $0.41 and $0.44/lb of N in the U.S. agricultural market. The prices of paraffin wax and Ca-LS vary between $600 and $1,000/metric ton and between $2,156 and $2,256/metric ton, respectively.…”

Capture and Release of Orthophosphate by Fe-Modified Biochars: Mechanisms and Environmental Applications

“…Previous studies at the Iowa State University have shown that biochar production is profitable as part of a fast pyrolysis biorefinery. Techno-economic analyses of fast pyrolysis biorefineries have estimated positive net present values while assuming a value for biochar of only $50–$100 per metric ton. − While economic analyses have not yet been completed on the process to produce the ISIB biochar for slow-release fertilizer, autothermal pyrolysis simplifies the reactor design and reduces energy input requirements, thus reducing capital and operating expenses . Additionally, the method by which the biomass is pretreated has been evaluated using other pretreatments, most notably sulfuric acid.…”

Techno-economic and greenhouse gas emission assessment of carbon negative pyrolysis technology

“…In addition, an LCA of biobased levoglucosan estimated its global warming potential to be half that of petroleum-derived chemicals 35 . TEA and LCA of an integrated pyrolysis and anaerobic digestion system for production of ethanol and phenolic compounds estimated the MFSP to be $1.21/gallon with net GHG emissions of -16.6 g CO 2e /MJ 13 .…”

“…35 TEA and LCA of an integrated pyrolysis and anaerobic digestion system for production of ethanol and phenolic compounds estimated the MFSP to be $1.21 per gallon with net GHG emissions of −16.6 g CO 2e per MJ. 13…”

“…Fast pyrolysis is the thermochemical conversion of biomass with the potential production of a wide range of products, including biofuels, fermentable sugars, and biobased chemicals. [12][13][14][15] Although biofuels from fast pyrolysis appear to be economically attractive, [16][17][18] technical challenges have hindered its commercial adoption. 19,20 Among these challenges is difficulty in providing energy to the reactor as the process is scaled up.…”