A Techno-Economic Analysis of Solid Acid Mechanocatalysis for Biomass Solubilization in the Production of Cellulosic Ethanol

Abstract

Cellulosic biofuels can serve as a sustainable, low-carbon alternative to petroleum-derived fuels. However, challenges currently exist with conventional methods of solubilizing lignocellulosic biomass into monomeric sugars for biochemical conversion that prevent widespread commercialization. Solid acid mechanocatalysis (SAMCP), a dry process that employs mechanical milling of biomass with solid acid catalysts to induce hydrolysis, is an emerging solubilization technique that could reduce the cost of biochemical processes relative to conventional methods. This thesis designed a commercial-scale cellulosic ethanol process using SAMCP to solubilize biomass. The base case and carbon capture scenarios’ techno-economic and lifecycle greenhouse gas (GHG) emissions performance were evaluated against National Renewable Energy Laboratory’s (NREL) cellulosic ethanol process, which used dilute acid pretreatment and enzymatic hydrolysis to solubilize biomass, to determine SAMCP’s performance in cellulosic fuel production. The base case SAMCP resulted in a 2016$ minimum ethanol price of $1.68/gallon and 72% lifecycle GHG emissions reduction relative to gasoline, 30% lower cost and 5% reduced GHG emissions compared to NREL, respectively. Capturing fermentation gases and plant emissions resulted in higher prices of $1.73/gallon and $2.34/gallon, respectively, and 105% and 191% lifecycle GHG emissions reductions relative to gasoline, respectively. These carbon capture designs break even with $60 per barrel crude oil at carbon prices of $20/ton CO2,eq and $50/ton CO2,eq, respectively. Solid acid mechanocatalysis could serve as a lower cost biomass solubilization method for cellulosic fuel production, but the reaction solubilization extent, the reaction product’s monomeric sugar and fermentation inhibitor content, and the product separation efficiency must first be verified at demonstration scale.