Environmental performance of olive stone-plastic waste activated carbon composites

The circular valorization of agricultural residues and plastic waste into functional materials is a critical challenge for sustainable water treatment technologies. In this study, activated carbon (AC) composites were produced by integrating olive stone (OS) and mixed plastic waste (MPW) into a carbon-polymer adsorbent, and their environmental sustainability was systematically evaluated using life cycle assessment (LCA). The OS-MPW AC composites exhibit low environmental burdens, with climate change (CC) impacts of 3.70 kg CO₂ eq. and an energy net (EN) of 100 MJ kg^-1. In contrast, commercial AC shows substantially higher impacts, with CC emissions of 4.8 kg CO₂ eq. and an EN of 125 MJ. In addition, the waste-derived composites demonstrate high adsorption performance toward Rhodamine-6G, achieving a maximum adsorption capacity of 669 mg g^-1, thereby reducing the amount of adsorbent required for effective pollutant removal. To capture both production efficiency and application relevance, LCA was conducted using two functional units: per kg of AC composite produced and per kg of dye adsorbed. Contribution analysis identifies pyrolysis and polymer dissolution as the dominant contributors to CC and EN. Sensitivity analyses further indicate that pyrolysis energy consumption is the most influential uncertainty parameter. Overall, the results demonstrate that OS and MPW can be effectively co-valorized into high-performance AC composites with favorable environmental profiles.