More than ethanol: a techno‐economic analysis of a corn stover‐ethanol biorefinery integrated with a hydrothermal liquefaction process to convert lignin into biochemicals

High‐value chemicals from lignin could increase the profitability of lignocellulosic biorefineries. Besides lignin from the paper and pulp industry, ethanol plants produce lignin as a waste; thus, the objective of this work is to evaluate the techno‐economics of integrating hydrothermal liquefaction of lignin to produce biochemicals within ethanol biorefineries. This paper evaluates a 2000 metric tonne per day (MTPD) corn‐stover biorefinery producing 61 MMgal/yr. of ethanol and different yields of lignin‐derived biochemicals. A minimum ethanol selling price (MESP) of $1.03 ± 0.19 per gallon was computed considering the production of lignin‐derived catechol, phenol, cresols, acetic acid, formic acid, furfural, and acetaldehyde. The most influential factors on MESP identified are fixed capital investment, internal rate of return (IRR), feedstock price, cresols, catechol, and acetic acid prices. In terms of costs, the total purchased equipment cost is $114.5 MM, total installed cost (TIC) is $345.7 MM, and total capital investment is $624.5 MM. However, ethanol biorefineries adopting this lignin‐to‐chemicals strategy could still face higher levels of price uncertainty. The hydrothermal liquefaction process for the production of lignin‐derived chemicals is in the early stages of development; thus more laboratory and pilot‐scale research is needed to establish its potential for commercialization.