Industrial symbiosis is assumed to create both environmental and economic benefits to the actors involved in exchanges of material and energy. However, quantifications of the economic and environmental performances of symbiotic activities are rarely performed and most of the literature available on industrial symbiosis analyzes the conditions for cooperation and uncovering new eco-industrial parks worldwide. Of the available quantifications, methods, impact categories, functional unit and other choices vary considerably. Furthermore, no clear guidelines are available for how to quantify the benefits or impacts of industrial symbioses. In order to understand what impacts or benefits industrial symbioses create a review of different approaches followed by recommendations from research in the biofuel industry will be provide.
The paper will review different approaches for quantifying the environmental performance of industrial symbioses from previous researchers and provide a methodology used in the authors’ research concerning industrial symbiosis in the biofuel industry based on life cycle assessment. The approach will provide guidelines to match life cycle assessment terms as a recommendation for other industries.
The research is based on the theories of life cycle thinking and life cycle assessment and uses these to find an approach to quantify the environmental performance of industrial symbiosis. The cornerstones of the research are therefore life cycle thinking and industrial symbiosis.
Much of the research available on quantifying industrial symbiosis is related to only one or a limited number of material or energy exchanges. The quantifications generally only provide one impact category, such as the emissions of CO2. Another important issue is what to measure the impacts against, i.e. the choice of a reference system.
Recommendations for the choice of functional unit, system boundaries, reference system and how to allocate impacts are thus provided. This relates to the “main purpose” of the symbiosis. In the case of biofuel production, the biofuels being produced, i.e. MJ per year of each respective fuel, are set as the functional unit. Allocation of impacts by the system expansion method is recommended in order to take care of any excess products produced in the system and avoided elsewhere which can better model the benefits of exchanging materials and avoiding inputs from outside the system. A hybrid model for system expansion is also applicable even with other allocation methods, e.g. energy and economic allocation.
The recommendations provided, based on the biofuel industry, may be applied in other industries. The research provides an approach to quantifying the performance of industrial symbioses and the benefits from the exchanges of material and energy.