Life Cycle Carbon Emissions Savings of Replacing Concrete with Recycled Polycarbonate and Sand Composite

Recent work demonstrated that 50:50 sand-recycled polycarbonate (rPC) composites have an average compressive strength of 71 MPa, which dramatically exceeds the average offered by commercial concrete (23.3–30.2 MPa). Due to the promising technical viability of replacing carbon-intensive concrete with recycled sand plastic composites, this study analyzes the cradle-to-gate environmental impacts with a life cycle assessment (LCA). Sand-to-plastic composites (50:50) in different sample sizes were fabricated and the electricity consumption monitored. Cumulative energy demand and IPCC global warming potential 100a were evaluated to quantify energy consumption and greenhouse gas emission associated with sand–plastic brick and two types of concrete, spanning the life cycle from raw material extraction to use phase. The results showed that at small sizes using Ontario grid electricity, the composites were more carbon-intensive than concrete, but as samples increased to standard brick–scale rPC composite bricks, they demonstrated significantly lower environmental impact, emitting 96% less CO2/cm3 than sand–virgin PC (vPC) composite, 45% less than ordinary concrete, and 54% less than frost-resistant concrete. Energy sourcing has a significant influence on emissions. Sand–rPC composite achieves a 67–98% lower carbon footprint compared to sand–vPC composite and a 3–98% reduction compared to both types of concrete. Recycling global polycarbonate production for use in sand–rPC composites, though small compared to the total market, could annually displace approximately 26 Mt of concrete, saving 4.5–5.4 Mt of CO2 emissions. The results showed that the twin problems of carbon emissions from concrete and poor plastic recycling could be partially solved with sand–rPC building material composites to replace concrete.