The potential contribution of industrial symbiosis to greenhouse gas emissions mitigation
Decarbonising energy-intensive material production processes as quickly and effectively as possible is a key challenge for policy-making to mitigate climate change. The global production of bulk materials such as steel, cement, paper, and aluminium has almost tripled over the past three decades. Strategies for increasing energy efficiency and material efficiency have been implemented to reduce specific energy demand as well as emissions. One option to reduce the overall greenhouse gas (GHG) emissions of industrial production is the use of by-products in so-called ‘industrial symbiosis’. The aim of this thesis is to estimate the potential contribution of industrial symbiosis to GHG emissions mitigation and to quantify the levels of material production and resource requirements on a pathway that leads to net zero emissions by 2050. The increase in industrial production and previous studies on industrial symbiosis and decarbonisation pathways for bulk materials are described in the first two chapters. A model for industrial production based on bottom-up production recipes is developed and validated in the third chapter. The model includes primary and secondary routes for major bulk material production processes. Using the model, chapter four provides a quantitative estimate of the global potential for industrial GHG emissions mitigation by industrial symbiosis in bulk material industries in two scenarios of symbiosis. The analysis with optimistic assumptions finds that emissions can be reduced by up to eighteen percent. This suggests that industrial symbiosis alone is not sufficient to achieve net zero emissions and unlikely to make a significant contribution to GHG emissions mitigation. The transition to net zero emissions in industrial production requires zero emissions resources, i.e., non-emitting electricity, biomass as well as permanent carbon capture and storage. The fifth chapter quantifies what bulk material production is possible under the condition of a transition to net zero emissions by 2050 for current trajectories of the deployment of those zero emissions resources. The results suggest that there is a significant gap between expected production and possible production levels under the constraint of net zero emissions. The latter are significantly lower than material demand in 2050 estimated by other models. To address this, a more rapid deployment of zero emissions resources and material efficiency strategies is required. Production processes with net zero emissions have different by-products than current production processes. Therefore, the transition and scale-up of new production routes, including secondary production, has significant implications for industrial symbiosis and GHG emissions in downstream processes (e.g., in cement production). The concluding discussion of the findings then describes policy implications and highlights areas for further research.
circular economy, industrial symbiosis, material efficiency, net zero emissions
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