Current systems analysis methods and practices and specifically waste LCA models most often represent and evaluate the waste management sector in a much too simplistic interaction with its surroundings, accounting for a minimum of probable future system interactions/ effects, many times through inconsistent methods and static representations of background systems. Their insufficiency in taking account of consequences of decisions towards implementation of different waste management strategies can compromise them as decision-supporting tools. As such, there is a need for advances in methodological aspects related to modelling effects/ interactions with surrounding systems, including better convergence with economic modelling methods.
This PhD work investigated the role and implications of mechanical pre-treatment and centralized sorting as a key waste management technology for strategies to achieve both resource and energy recovery optimizations and to minimize climate impacts of waste management in the context of future framework conditions.
The key contributions and insights offered by this PhD work include:
• A review of the current state in technical development, process efficiency and economic aspects of sorting and separation systems - found overall a high level of technical maturity; these systems have significant potential to support, or even be an alternative to, source separation and separate collection programs for certain recyclable materials, in areas where such programs are difficult to implement or optimize, such as urban agglomerations.
• Alternative MSW management systems were simulated and evaluated, comprising numerous combinations of separate collection and downstream treatment/handling approaches – from a materials flow approach, I find that diversion for recycling could be maximized by a combination of separate collection and centralized sorting of mixed waste streams.
• Alternative systems were assessed and compared against a large variety of background system scenarios representing the most probable future development of the Danish energy system – source separation and biogasification of organic streams were found to align and even support the decarbonisation of the energy systems while ensuring nutrient recycling; climate benefits from waste-derived energy by combustion-based WtE will be offset by direct combustion emissions in the future; nevertheless, under present conditions, maximizing operation, even by including waste imported from countries that landfill is still highly preferable.