Turning waste into value

Abstract

This original research contributes to enhancing the viability of biorefineries through recovering valuable by-products from the liquid remaining after the biomass pretreatment by hot liquid water. A novel downstream processing method is developed for the recovery of acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF) by enhanced distillation. The major challenge in this research is the processing of the highly diluted initial solution (>96 wt% water) and the thermodynamic limitations owing to possible formation of several azeotropes. This new process recovers 78.7% of the acetic acid (99.8 wt%), while the rest of it is recycled back to the biomass pretreatment step together with most of the separated water from the initial solution. Over 99.5% of formic acid, furfural and HMF is also recovered, at purities of 74.7, 98.0 and 100 wt%, respectively. Vapor recompression and heat integration are implemented to decrease the energy use. The results demonstrate a 77.4% decrease in total annual costs (from $3.44 to 0.78/kg_product), a 75.0% reduction in minimum average selling price (from $3.50 to 0.87/kg_product), an 81.1% reduction in energy requirements (from 77.41 to 14.66 kW_thh/kg_product) and an up to 99.7% decrease in CO₂ emissions (from 11.17 to 0.03 kg_CO2/kg_product).