A stakeholder decision and road-network-based deterministic model to simulate material flows in regional scale industrial symbioses

Industrial Symbiosis (IS) projects are today well known for their contribution to sustainable development. Designing IS projects implies modelling the quantity of material flows between economic components (ECs), in particular to evaluate the environmental and economic gains obtained through more material circularity and use efficiency. The Industrial Symbiosis concept is now being applied to activities distributed over territories much wider than industrial parks. For such setups, existing modelling methods are becoming strained by the number of economic components involved, their dissemination within heterogeneous landscapes and the resulting complexity of the exchanges. In this paper, we propose a generic, spatially explicit simulation model based on stakeholder decision rules to study regional scale flows quantification between ECs in n-n IS networks. Our approach introduces the use of the Gale-Shapley stable matching algorithm for addressing the many-to-many supply-demand matching problem. The method is deterministic and provides stable solutions that optimise the individual objectives of the ECs. A second introduction considers using transport cost along the road network among the decision rules when ECs preferences are ordered. This solves the issue of correctly estimating travel distance in heterogeneous landscapes where it can be significantly different to the distance as the crow flies. We tested the model with the implementation of two real and concrete case studies related to the bioeconomy of a tropical island: (i) collective storage of fodder and (ii) co-composting platforms. The outputs of the model make it possible to compare scenarios based on EC satisfaction relative to supply and demand as well as the total distance travelled along the road network. Finally, we discuss the limitations and genericity of the model to explore diverse industrial symbiosis projects.