A techno-economic analysis of thermochemical pathways for corncob-to-energy: Fast pyrolysis to bio-oil, gasification to methanol and combustion to electricity

Global warming concerns have driven developments in carbon neutral energy, pulling initiatives on biofuels production. However, the low bulk density and low specific energy of biomass refrain its widespread use due to logistic costs comprising harvesting and collection, storage, pretreatments and transportation. This work approaches increasing land energy productivity by thermochemical conversion of residual biomass to energy products, identifying the best options in terms of energy efficiency and economic indicators. Techno-economic performance of three corncob-to-energy pathways is investigated: gasification to methanol, fast pyrolysis to bio-oil and combustion to electricity. Fast pyrolysis allows higher energy recovery in its products (79%) than biomass gasification to methanol (53%), with biomass densification (volume reduction) of 72.7% and 86.2%, respectively. The combustion route presents net efficiency of 30.2% of biomass low heating value (LHV). All alternatives are economically feasible provided biomass cost is lower than US$75.5/t. The minimum allowable product prices for economic attractiveness of gasification, combustion and pyrolysis routes are US$305/t methanol, US$80.1/MWh electricity and US$1.47/gasoline-gallon-equivalent bio-oil. Despite its vulnerability to price volatility, gasification presents the highest net present value, seconded by the combustion route, which has lower medium-term payback and investment than gasification due to its process simplicity.