Deep Eutectic Solvent Pretreatment for Cellulose Enrichment from Coffee Waste

The treatment of coffee silverskin (CSS), a waste stream from the coffee industry, through deep eutectic solvents (DES) was studied. Choline chloride-based DES mixtures were checked by using a lactic acid (LA) hydrogen bond donor. The effect of time, temperature and biomass:DES ratio on the dissolution of lignin and hemicellulose was analyzed. Maximum hemicellulose reduction was from 28.15% to 3.37% at 60 °C and 1 h and maximum lignin reduction was from 33.1% to 20.03% at 90 °C and 5 h. Additionally, it was found that the optimum operating conditions obtained were 3 h, 120 °C and biomass:DES ratio (1:10), which led to 8.02%, 29.31% and 36.48% hemicellulose, lignin and cellulose content, respectively. Consequently, DES pretreatment can be considered a promising approach to obtain cellulose-enriched coffee silverskin solids under lower-temperature conditions than many conventional lignocellulosic biomass pretreatments. However, further downstream validation is required to assess their suitability for paper, textile, or food-packaging-related applications.