What Contribution Could Industrial Symbiosis Make to Mitigating Industrial Greenhouse Gas (GHG) Emissions in Bulk Material Production?

In industrial symbiosis, byproducts and wastes are used to substitute other process inputs, with the goal of reducing the environmental impact of production. Potentially, such symbiosis could reduce greenhouse gas emissions; although there exists literature exploring this at specific industrial sites, there has not yet been a quantitative global assessment of the potential toward climate mitigation by industrial symbiosis in bulk material production of steel, cement, paper, and aluminum. A model based on physical production recipes is developed to estimate global mass flows for production of these materials with increasing levels of symbiosis. The results suggest that even with major changes to byproduct utilization in cement production, the emission reduction potential is low (7% of the total bulk material system emissions) and will decline as coal-fired electricity generation and blast furnace steel production are phased out. Introducing new technologies for heat recovery allows a greater potential reduction in emissions (up to 18%), but the required infrastructure and technologies have not yet been deployed at scale. Therefore, further industrial symbiosis is unlikely to make a significant contribution to GHG emission mitigation in bulk material production.