Filtering ‘3–2’ industrial symbiosis networks at a carbon-intensive cluster in a small island developing state to reuse CO2 and water

Small island developing states (SIDS) face internal and external pressures for more sustainable manufacturing e.g., economic and ecological water provision, and anti-carbon leakage tariffs. As SIDS have special developmental challenges, locally appropriate strategies are needed. In one of these SIDS, Trinidad and Tobago, is a carbon-intensive industrial cluster of global standing, the Point Lisas Industrial Estate (PLIE). So, to investigate ‘3–2’ industrial symbiosis (IS) on the PLIE, a simple enterprise input-output MILP model of a representative IS network was developed. Different quality wastewater streams and high-purity process CO₂ from ammonia processes were selected as materials to be reused in: existing petrochemical plants, a mineral carbonate factory and a propylene carbonate plant. To filter the IS relations, economic and environmental objectives were set for each material. Combining economic objectives left a tri-objective problem, which was resolved with ε-constraint optimization and multi-criteria decision-making methods. Kleinberg's hub and authority scores were found to give beneficial insight into the solved IS networks. Potential revenue-generating opportunities were uncovered for sharing and reusing water and process CO₂. The results suggest adding two proposed carbonate factories could increase the mass of CO₂ reused in the cluster by 10.4 % and mitigate releasing 5 Tg/y of rejected desalination brine.