Environmental impact assessment of six starch plastics focusing on wastewater-derived starch and additives

Starch plastics are developed for their biobased origin and potential biodegradability. To assist the development of sustainable starch plastics, this paper quantifies the environmental impacts of starch plastics produced from either virgin starch or starch reclaimed from wastewater. A cradle-to-factory gate life cycle assessment is conducted for six different starch plastic compositions, which include representative amounts of additives such as compatibilisers. Starch plastics are shown to enable reductions in greenhouse gas (GHG) emissions and non-renewable energy use (NREU), but have higher eutrophication potential and require more agricultural land use compared to common petrochemical plastics. The GHG emissions savings are strongly influenced by the plastic's composition, with some grades offering an 85% reduction and others an 80% increase compared to the petrochemical counterpart (on a same weight-basis). Additives can account for up to 40% of the GHG emissions of starch plastics. The highest GHG savings are obtained when components such as PBAT and PBS are minimised, while starch, natural fibres and mineral fillers are maximised. Using reclaimed starch instead of virgin starch leads to modest decreases in NREU and GHG emissions (< 10% in most cases), but up to 60% reductions in eutrophication and agricultural land use.