Conference Dates

June 5-10, 2016


The waste streams of society contain a substantial potential of material and energetic resources. The benefits of its utilization, however, depend on the waste management strategy applied. The present study aims at environmentally optimizing the Swiss municipal solid waste (MSW) management system by using the combination of material flow analysis (MFA), life cycle assessment (LCA), and mathematical optimization techniques. MFA supports decisions in resource management providing an understanding of the waste management system, providing information about capacities of treatment options, and assists in priority setting (Brunner and Rechberger 2004). MFA does, however, not provide information on the environmental impacts associated with resource management options. Comparative assessments of different products and processes can be carried out with LCA, but typically LCA is performed related to a so-called “functional unit” neglecting overall resource availabilities and limitations. Although there are already some links between MFA and LCA, the two methods are rarely used in a fully integrated way (Vadenbo et al. 2014a, 2014b). The use of a limited set of scenarios for the investigated systems, often used in MFA and LCA, can be avoided by applying linear programming extension of matrix-based LCA to derive the optimal system configuration. Within this study, a national MFA of the MSW management system was performed highlighting current mass flows and treatment options for all waste materials. The MFA defines the functional unit of the system, i.e. the final demand for treatment of these waste amounts. Based on the MFA, inventories for the LCA are established. Combining MFA and LCA allows for both, assessing environmental impacts and considering system constraints, e.g. capacity restrictions and resource availability of waste. For MSW incineration (MSWI), two key capacity constraints have to be considered: Firstly, the upper capacity constraint for the quantity of ingoing streams and secondly, the annual gross thermal capacity. For recycling processes the throughput is limited in terms of quantity. Figure 1 shows a schematic representation of the investigated Swiss MSW management system including the recycling fractions paper, cardboard, PET, tinplate, aluminum and glass as well as the mixed residual waste. Resource management options available for the waste streams are determined from the current MFA and also shown in Figure 1 (Haupt et al, submitted). The total input in the system is 5.4 million tonnes of waste (Haupt et al, submitted). In the optimization, this amount of waste needs to be treated in all solutions as a system requirement. In the multi-objective optimization, the optimal mass flow distribution over each decision node (marked as circle in Figure 1) is determined. While the Swiss MSW management currently already performs rather well, with 50% MSW going into material recycling and the other half into MSWI with energy recovery, there are still some environmental improvement potentials concerning both energy and material recovery.

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