Life cycle assessment of converting waste plastics into activated carbon: A comparative analysis of HDPE, LDPE, PS, and PP feedstocks

Activated carbon (AC) is an important adsorbent for environmental treatment; however, the traditional method of production is energy-consuming and chemical-intensive. AC from valorized post-consumer plastics is a promising waste-to-resource route. This study presents a cradle-to-gate LCA of AC derived from polypropylene (PP), polystyrene (PS), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), evaluated across three scenarios—baseline, recycling-integrated, and landfill disposal. The effects of polymer type and char yield are demonstrated. PP had the highest global warming potential (31.41 kg CO 2 eq) in the baseline, and HDPE presented the lowest global warming potential (17.79 kg CO 2 eq). Including 20% recycling, all polymers had consistently lower burdens, with percentage reductions of 6.3% for PP, 7.2% for PS, 9.5% for LDPE, and 7.2% for HDPE. At 30% recovery, LDPE and HDPE showed the greatest reductions, at 14.2% and 12.7%. In contrast, landfill resulted in apparently lower GWPs (0.5–2.4 kg CO 2 eq versus 18–31 kg CO 2 eq, 92 to 97% reduction), but higher toxicological burdens for freshwater ecotoxicity (+78%), marine ecotoxicity (+74%), and human non-carcinogenic toxicity (+192%). Sensitivity analysis confirmed electricity consumption as the dominant driver, with effects evident at a 1%. At the ±10% accounting for electricity variation, PP’s GWP varied from 29.33 (–6.6%) to 33.45 (+6.5%) kg CO 2 eq, and HDPE ranged from 17.72 (–0.4%) to 18.29 (+2.8%) kg CO 2 eq. Overall, the results indicate that polymer-to-AC valorization, when coupled with recycling and electricity-saving, provides an opportunity to mitigate climate without the unsustainable practice of landfilling.