Scientific abstract:

With an annual production volume of 4.3 Gt, cement is an important construction material, indispensable for the provision of various socio-economic services. Cement is a major driver for climate change, emitting 8% of the global energy-related greenhouse gases (GHG). Moreover, direct GHG emissions from cement production have increased by 1.5% per year between 2015 and 2021, jeopardizing the sector’s efforts to reach the emission reduction targets of the Paris agreement. Thus, long-term transition pathways towards a global low-carbon cement industry are needed. Ideally, these pathways are developed using a systemic approach, e.g. in coherence with macro-economic developments, such as decarbonization of other sectors, and considering biophysical limits, such as availability of resources. Moreover, they need to overcome the carbon-tunnel vision of existing studies by also considering burden shifting to other environmental impacts. The goal of this study is to assess potential environmental impacts of possible transition pathways to low-carbon cement production for different climate targets using prospective LCA (pLCA). We use global cement production scenarios from the Integrated Assessment Model (IAM) IMAGE to improve the macro-economic coherence of the transition pathways. We assess 3 scenarios: a business as usual (SSP2-Base), 2°C-compliant (SSP2-2.6) and 1.5°C-compliant (SSP2-1.9) scenario. They cover 26 world regions and the years 2020 to 2060. The IAM scenarios are integrated into the life cycle inventory database ecoinvent v3.8 using the python package premise. They are complemented with IMAGE-based background scenarios for electricity, fuels, transport and steel, to include supply chain decarbonization effects. This prospective LCA study is cradle-to-gate and, for consistency, only includes technological changes foreseen by the IAM. As such, technologies at low technological readiness level or demand-side mitigation options are not considered. Our results show that by 2060 the climate change impact of the cement sector is substantially reduced in the more climate-ambitious scenarios compared to the business as usual scenario. This reduction is mostly caused by a large-scale roll-out of CCS and a higher share of bio-fuels, while efficiency improvements only contribute to a lower extent. We found that decarbonizing electricity generation in the background can considerably reduce CO2 emissions for cement production. Despite substantial reductions in CO2 emissions, net-zero cement production is not reached globally by 2060. The residual emissions between 2020 and 2060 claim a significant part of the remaining global carbon budgets of the scenarios. Furthermore, we found that the reductions in climate change impacts coincide with a burden shift towards other impact categories, such as land use and material resources, and a higher future energy demand. Rapid and drastic measures are required to close the gap between the currently slow deployment rate of CCS in the cement industry and the high CCS adoption rates required in the climate-ambitious scenarios over the next decade. Policy makers must also ensure that the high demand for biofuels and low-carbon electricity required for economy-wide decarbonization can be met. Future research could explore if expanding this production-focused model to include mitigation levers along the entire cement value chain could lead to feasible pathways to net-negative cement production.