The Road to Biorenewables: Carbohydrates to Commodity Chemicals

The pressing need for climate change mitigation has focused attention on reducing global emissions of carbon dioxide by effectuating the transition from fossil-based chemicals manufacture to a carbon neutral alternative based on lignocellulosic waste. The first step involves fractionation of the lignocellulose into cellulose, hemicellulose, and lignin. Subsequently, a cellulase enzyme cocktail is used to catalyze the hydrolysis of the polysaccharides into their constituent sugars. This is followed by selective conversion of the carbohydrates into commodity chemicals using a variety of sustainable bio- and chemocatalytic methodologies. These include, inter alia, fermentative production of alcohols, diols, and carboxylic acids and a variety of chemocatalytic reductions and oxidations. Hence, the transition from fossil feedstocks to lignocellulose represents a switch from hydrocarbons to carbohydrates as the primary basic chemicals. To compare these renewable biomass-based routes with their petrochemical equivalents, it is necessary to develop reliable sustainability metrics.