Life cycle assessment and industrial synergy for carbon reduction: A circular economy approach

In the face of the climate change crisis, circular economy (CE) is put forward as a promising key to the sustainable development goals (SDGs) riddle. In this context that affects developed and developing countries alike, circular initiatives arise, such is the case for Morocco where an industrial synergy based on the CE concept of 'waste is food' can be envisioned between the local phosphate and cement industries. In order to support and guide this initiative, a life cycle assessment (LCA) was conducted to compare the environmental performance of the production of ordinary Portland cement (OPC), limestone calcined clay cement (LC3) and a phosphate waste-based cement known as calcined marl cement (CMC). In addition to a mass-based functional unit (FU), a performance-based FU was adopted to account for the 'longer service lives' concept of CE, which necessitated the estimation of cements' service lives and CO₂ uptake potentials. Results show that CMC and LC3 production respectively reduce impacts on global warming by 23 % and 60 %, while the country aims for a 18.3 % reduction by 2030; mineral resource scarcity is reduced by 30 % and 48 %; and other impacts by 10 % and 40 % compared with OPC. This is chiefly due to CMC and LC3's better durability performance and lower clinker content. Using LCA results, carbon tax was pre-estimated to drop by 9 and 18$/ton of cement for CMC and LC3. A life cycle costing and a social LCA must be conducted to comprehensively guide stakeholders in their decision-making process regarding a phosphate-cement synergy.