Here we bring biogeochemical thinking to the world of plastics and waste. Our group contributes to the Solving Plastic Waste CRC and the 4R Waste Hub, studying the occurrence, transformation and impacts of plastics and microplastics in soils and catchments, and developing strategies for reduction, recycling, recovery and reuse. We combine analytical chemistry, soil ecology and digital sensing to understand how waste-derived products, biochar and organic residues can be safely and effectively returned to land as part of a circular, climate-neutral economy.