Life cycle comparison of biochar and activated carbon adsorbents for PFOS removal: Impacts and disposal pathways

This study carries out a comparative life cycle assessment (LCA) to quantify the environmental impacts associated with different options for the treatment of perfluorooctane sulfonates (PFOS). Four carbonaceous materials are analyzed: Metal oxide sawdust biochar (MOSB), Corn straw biochar (CSB), Bamboo activated carbon (BAC), and Commercial granular activated carbon (GAC). The key impact categories included Human Carcinogenic Toxicity, Marine Ecotoxicity, Freshwater Ecotoxicity, and Freshwater Eutrophication. Results showed GAC with the lowest environmental impacts (≤ 1 % of impacts across categories), followed by BAC (1–2 %), CSB (5–7 %) and MOSB with the highest environmental impacts (> 90 % across categories). Electricity, nitrogen, and water are the main contributors to over 90 % of the environmental impacts of the adsorbents. In terms of energy, MOSB uses the most energy (0.72 MJ), mostly from non-renewable sources, while GAC is the most energy-efficient, using only 0.0023 MJ. Regarding the final waste scenario, landfilling presented lower environmental impacts than incineration for MOSB, CSB, BAC, and GAC in general, except for land use and mineral resource scarcity. The treatment of hazardous waste causes over 90 % of the total impacts, while transportation has minimal effects. Sensitivity analyses on yield, electricity mix, water source, and ReCiPe time-horizon assumptions confirmed that the relative ranking of adsorbents remains stable, even though absolute impact levels vary. The findings of this study indicate the use of GAC as a promising method for producing high-quality sorbents that can effectively remove PFOS from water, with the lowest environmental impacts associated. • GAC shows the lowest environmental impacts across categories. • MOSB accounts for > 90 % of total impacts. • Electricity, nitrogen, and water drive over 90 % of impacts. • MOSB highest energy use; GAC most efficient. • Landfilling has generally lower impact than incineration.