A closed-loop biorefinery could dramatically lower the cost of biofuels and related products. In this approach, the refinery produces the solvents it needs, rather than “importing” them. Scientists at the Joint BioEnergy Institute are developing a closed-loop biorefinery concept that uses waste lignin as a potential process solvent. How? They synthesized a new and renewable class of deep eutectic solvents. These solvents work well. When mixed with other liquids and used for biomass pretreatment, these solvents released sugar from grassy feedstocks for fuel and chemical production.