Multi-products co-production improves the economic feasibility of cellulosic ethanol: A case of Formiline pretreatment-based biorefining

Abstract

The economic feasibility of cellulosic ethanol is still poorer than that of grain-based ethanol because of the difficulty in lignocellulose saccharification and more complicated production process. Pretreatment greatly affects the production cost of cellulosic ethanol. In this work, Formiline pretreatment based on formic acid delignification was used to achieve a fractionation of wheat straw for co-producing ethanol, furfural and high-purity lignin. Techno-economic assessment was performed and compared with that of dilute acid-based process. For a plant with a capacity of ∼ 30,000 tonnes of ethanol/year, Formiline process required a total amount of wheat straw of 201,992 dry tonnes/year with a total capital investment of 176 MM USDs (in 2016), being 40% higher than that of dilute acid process. The total production cost was estimated to be 1,636 USDs/tonne of ethanol when no by-product credits were considered, being 42.2% higher than that of dilute acid process. However, since high value-added products such as furfural and high-purity lignin were co-produced, the production cost of ethanol with consideration of the by-product profits was significantly reduced to 196 USDs/tonne. Formiline process thus could achieve a positive value-added increase (+99 USDs/tonne of wheat straw) for wheat straw conversion; however, dilute acid process had a negative value-added increase (-68 USDs/tonne of wheat straw) if only ethanol was produced. The obtained results indicate that the production cost can be well reduced by increasing substrate-to-product conversion, reducing cellulase loading and decreasing energy consumption for solvent recovery; however, co-production of multi-products provides an promising way to increase the potential revenue.