PHA bioplastic: A value-added coproduct for biomass biorefineries

The petroleum industry has optimized profits by producing value-added coproducts, such as plastics and chemicals, in addition to primary liquid fuels. A similar coproduct strategy applied to biorefineries processing cellulosic biomass to liquid fuels and/or energy would transform a technology that is marginally economic, depending on oil prices, to a sustainable business with enhanced revenue streams from multiple coproducts. The challenge is finding a biobased coproduct that is compatible with a biorefinery scenario and where markets warrant its production on a similar scale as liquid fuels and/or energy. Polyhydroxyalkanoate (PHA) bioplastics represent a coproduct that would be entirely compatible with either production of liquid fuels by hydrolyzing the residual biomass after PHA extraction or by alternative thermochemical processes. PHA bioplastics possess properties making them suitable replacements for many of the applications currently served by petroleum-based plastics, thus providing tremendous market potential. Proof-of-concept technology for production of these plastics in several crops of agronomic interest has been demonstrated. In this review, we show that the potential for developing biomass-based biorefineries producing liquid fuels and a value-added coproduct is both real and realizable. Examples using switchgrass producing PHA bioplastics as a coproduct are described. (C) 2009 Society of Chemical Industry and John Wiley & Sons, Ltd.