Environmental impact tradeoff considerations for wheat bran-based biocomposite

Abstract

Bio-based materials are increasingly proposed as sustainable alternatives to fossil-based products. Before commercialization, however, the environmental performance of bio-based materials must be evaluated to ensure the sustainability goals are met. Biocomposites derived from natural fibers hold promises for achieving the desired sustainability while offering competitive performance. Here, we assess the sustainability tradeoffs of using wheat bran, a by-product of milling wheat grain, for biocomposite production. We design two systems to evaluate such decision from the perspectives of flour and biocomposite producers. Each system is compared to a business-as-usual scenario: 1) flour system uses bran at the end of grain milling for either fiber production or disposes of it as waste, and 2) biocomposite system compares producing a biocomposite with 30% bran fiber/70% polypropylene with a 100% polypropylene. Our comparative life cycle assessment shows that in flour system, using wheat bran for biocomposite production rather than wasting it, lowers the overall environmental impacts including global warming and fossil fuel depletion mainly due to bran fiber replacing polypropylene, and avoiding carbon dioxide emissions from bran degradation. In system 2, mixing bran fiber in biocomposite lowers greenhouse gas emissions (1470kgCO2eq/t) and fossil fuel depletion (2130 MJ surplus/t) compared to the fully petroleum-based material. We discuss several upstream (e.g. reducing the chemicals during wheat cultivation) and downstream (e.g. sodium hydroxide consumption during fiber extraction) options that can help improve the overall environmental performance of the studied systems. Our study provides decision-making information for a variety of stakeholders including wheat producers, millers as well as composite industries.