Towards carbon-negative primary aluminium production: Integrating biomass resources and renewable electricity

Decarbonizing heavy industries such as aluminium production is critical for achieving global climate targets. Despite increasing recycling rates, demand for primary aluminium is projected to increase by 20% over the next 25 years. Primary aluminium is largely produced via the Hall–Héroult process, which is both energy-intensive, consuming 13,000–15,000 kWh E E /t A l , and dependent on fossil-derived carbon anodes. This results in a global average carbon footprint of 12–15 t CO 2 /t Al , with the International Aluminium Institute reporting a value of 14.8 t CO 2 /t Al in 2023, 60% of which was produced in China. This study aims to synthesize and evaluate decarbonization pathways for primary aluminium production by investigating alternative alumina reducing agents (biochar and renewable hydrogen) and assessing their integration with secondary aluminium processes and a district heating network. The analysis is conducted through a total site optimization framework that incorporates waste heat recovery, seasonal resource switching, and biogenic CO 2 mineralization. Results indicate that a net-zero to net-negative carbon footprint can be achieved, ranging from –0.5 to 0.2 t CO 2 /t Al for the presented case study. Biomass-based pathways were found to deliver the highest CO 2 abatement potential, while electricity-dependent pathways face higher costs and grid-related emissions. Among the evaluated options, the bio-hydrogen scenario achieves the most favourable balance between cost, energy use, and environmental performance. These findings demonstrate that carbon-negative aluminium production is feasible through the integration of renewable resources and process-system optimization. • Fossil-free aluminium smelting is enabled using biochar or renewable hydrogen. • Integrated biomass gasification supplies on-site fuels and reducing agents. • Waste heat recovery increases efficiency and allows onsite electricity generation. • Site-wide optimization results in net-negative aluminium production. • Bio-hydrogen route delivers lowest cost and highest renewable energy share.