Cement decarbonisation in Aotearoa (New Zealand) – A critical review of the option space
Cement manufacturing produces around 5-8% of anthropogenic carbon dioxide emissions globally, contributing to climate change. New Zealand’s commitment to net-zero long-lived greenhouse gas (GHG) emissions by 2050 requires its emissions from cement consumed, mainly ordinary Portland cement (OPC), to be eliminated or offset. OPC is used to build essential buildings and infrastructure (B&I), but its production is challenging to decarbonise because over half the process emissions come from limestone calcination. This research maps the full range of technical options available for decarbonising cement in New Zealand. It then critically assesses which option combinations are most suitable, based on a framework of criteria including: GHG emission reduction potential, economic viability, technical viability, and externalities. By sorting cement decarbonisation options into groups, nine decarbonisation ‘levers’ emerged from the analysis, which reasonably comprehensively capture the range of options available. These include: 1) Reduce downstream demand for B&I; 2) Build longer-life B&I; 3) Build more materially efficient B&I; 4) Use alternative materials to concrete; 5) Use alternative binders to OPC; 6) Use alternative fuels for cement production; 7) Make cement production processes more efficient; 8) Recycle or reuse cement; and 9) Offset cement emissions using carbon dioxide removal (CDR). However, this analysis suggests there are two high-level strategies to decarbonise OPC. Strategy A is to stop using OPC by substituting with alternative materials and binders. Strategy B is to continue using OPC and use CDR to offset any residual GHG emissions. Because strategy B relies on speculative CDR technologies, and involves unsustainable processes, it is not considered a viable long-term solution for decarbonising cement in New Zealand. Strategy A should therefore be facilitated by the New Zealand government through support in the following areas: building codes and standards; education; public procurement; research and development; and infrastructure planning and investment. Further measures should be implemented to manage an expected increase in demand for bioproductive land, an increase in building material prices, and impacts on the cement production and construction workforces. Based on this analysis, the government should also ensure New Zealand cement producers are subject to a carbon price, and that appropriate border adjustments are applied to prevent emissions leakage and offshoring of the environmental and social impacts of building material production.