A comparative life cycle assessment of coal-tar pitch-based and bio-pitch-based carbon anode production for sustainable aluminium

The carbon anodes used in aluminium production are conventionally produced using coal-tar pitch (CTP), a fossil-based binder associated with greenhouse gas emissions and harmful pollutants such as polycyclic aromatic hydrocarbons. These emissions contribute to climate change, human health impacts, and other environmental effects. To support global decarbonization goals and meet growing aluminium demand sustainably, the industry is exploring renewable sources of carbon. Bio-pitch (BP), a biomass-based binder, has been proposed as an alternative for CTP to produce anodes. Although BP has shown promise at the laboratory scale, its environmental performance must be evaluated before industrial adoption. This study presents a comparative life cycle assessment (LCA) of CTP- and BP-based anode production. The research builds upon an initial LCA of CTP-based anode production, which identified the environmental impacts of anode production processes. The evaluation uses the ReCiPe midpoint method in the openLCA software with the Ecoinvent database. Results indicate that replacing CTP with BP reduces CO 2 emissions by 15 % per t anode. When anode consumption in electrolysis cells is included, CO 2 emissions per t Al decrease by 8 %. Sensitivity analysis shows that increasing the coking value of BP from (30 to 50) % further decreases anode-related CO 2 emissions by 10% relative to CTP-based anodes. A second sensitivity scenario demonstrates that BP remains environmentally advantageous even if net carbon consumption increases by 7 kg/t Al. The study also identifies reductions in human toxicity impacts and fossil energy resource use, alongside an expected increase in land use due to biomass sourcing.