Separation and Processing of Coffee Chaff By Deep Eutectic Solvents

Many methods have been used to process biomass unsuitable as animal feed for various uses. However, most of these processes are environmentally hazardous. We have focused on the valorization of the waste biomass coffee chaff using a solvent made of non-toxic, biodegradable components. Deep eutectic solvents (DESs) have low volatility and are low cost, non-flammable, nontoxic, and highly biodegradable. Our chosen secondary agricultural residue, coffee chaff, is generated in coffee processing. Coffee chaff or “silverskin” is the waste formed when raw coffee beans are roasted. Its low density makes it expensive to ship for valorization. We pre-treated coffee chaff with three different DESs: formic acid + choline chloride (FA:CC), lactic acid + choline chloride (LA:CC), and acetic acid + choline chloride (AA:CC). Little is available in the literature about coffee chaff upcycling because they are a niche waste. We found that DES pretreatment can separate lignin from coffee chaff, making lignin precipitated from the DESs and the biomass solid product residue both more dense and suitable for pelletization.