Systems Analysis for Eco-Industrial Development : Applied on Cement and Biogas Production Systems

Sammanfattning: Our industrial systems are not sustainable—a major challenge which demands several types of responses. Eco-industrial development can be seen as such a response, with the goal to establish industrial systems that are both ecological and economical. Industrial Ecology is another closely related response. It is based on the idea that natural systems can be used to understand how to design sustainable industrial systems, for example, by shifting from linear industrial processes to cyclic systems, where waste streams can be avoided or minimized through utilization as raw materials for other processes. In this thesis, the possible contributions of industrial ecology/symbiosis to eco-industrial development are investigated through the use of systems analysis approaches. Two systems analysis methods are used: life-cycle assessment and multi-criteria analysis. These methods are applied on two types of industrial systems: cement and biogas.Cement is among the most used materials in the world with extensive resource consumption and environmental impact, manifested for example by the high levels of CO2 emissions. Multi-criteria analysis was used to identify, classify, and assess different measures to improve the climate performance of cement production, while life-cycle assessment was employed to quantify the CO2 emissions. Combined, multi-criteria analysis and life-cycle assessment were used for an integrated assessment of different eco-industrial development paths. Most of the feasible and resource-efficient improvement measures were related to utilization of secondary resources, for example minimizing the clinker content of the cement by replacing it with by-products from steel and iron manufacturing, or using refuse-derived fuels. Effective utilization of these secondary raw materials and fuels can be achieved through industrial symbiosis.Biogas is viewed as part of a larger transition towards a bio-based economy where resources—bio-materials and bio-energy—are used in a cascading, circular, and renewable manner. Multi-criteria analysis was used to assess the feasibility and resource efficiency of using different types of biomass as feedstock for biogas and biofertilizer production. In addition to aspects such as renewable energy and nutrient recycling, cost efficiency, institutional conditions, environmental performance, the potential per unit, and the overall potential were considered. In another study, life-cycle assessment was used to analyze the environmental performance of biogas production from source-sorted food waste using a dry digestion process. The study showed that the performance of this dry process is superior to most of the existing wet biogas processes in Sweden. The critical sources of uncertainty and their impact on the overall performance of the system were analyzed. Factors influencing methane production, as well as processes related to soil after the digestate is applied as biofertilizer on land, have the greatest influence on the performance of these systems.For both cement and biogas systems industrial symbiosis involving collaboration and better utilization of local/regional secondary resources, can result in resource-efficient eco-industrial development. Life-cycle assessment and multi-criteria approaches can serve as two complementary methods for investigating the feasibility, potential, and resource efficiency of different development paths. These approaches can provide input into decision-making processes and lead to more informed decisions.