Life cycle assessment of electrocoagulation versus chemical coagulation for automotive cataphoresis wastewater: the role of electrode material and electricity source

Abstract

Electrocoagulation (EC) is widely promoted as a dosing-free alternative to conventional coagulation, yet life-cycle comparisons of the two remain scarce for industrial effluents. This study compares three EC electrode configurations (Al–Al, Fe–Fe and a hybrid Fe–Al) with poly-aluminium chloride (PAC) coagulation for automotive cataphoresis wastewater, using operating data from a vehicle manufacturing plant in Bursa, Türkiye. A cradle-to-grave life cycle assessment per 1 m 3 of treated wastewater was performed with SimaPro 9.6, the ecoinvent 3 cut-off database and ReCiPe 2016 (H) midpoint and endpoint methods. Chemical coagulation produced lower impacts than every EC configuration in all eighteen midpoint categories (ratios of 0.08 to 0.53 relative to the best EC configuration) and an endpoint single score of 141 mPt against 795–1100 mPt for EC. Human health damage dominated in all systems (≈97%). Electricity consumption (5.55–6.90 kWh m −3 for EC against 0.12 kWh m −3 for chemical coagulation) and sacrificial electrode production, acting through primary metal manufacture and co-incineration of the resulting metal hydroxide sludge, governed the difference. A renewable electricity scenario reduced EC global warming impacts by 17–26%, yet under full wind supply the best EC configuration remained 4.4 times the chemical coagulation baseline, and 4.9 times at an energy demand representative of optimised installations (2 kWh m −3 ). Monte Carlo simulation confirmed the ranking in all 10,000 paired iterations. The environmental disadvantage of EC is therefore governed by sacrificial metal consumption and the resulting hydroxide sludge rather than by electricity, and would not be resolved by grid decarbonisation.