Future waste treatment and energy systems--examples of joint scenarios

Globally differentiated effect factors for characterising terrestrial acidification in life cycle impact assessment

To assess terrestrial ecosystems damages from acidification, life cycle impact assessment (LCIA) can be applied using characterisation factors, which integrate the quantification of adverse effects via effect factors (EFs), linking decreasing soil pH to declines in species richness. With a species coverage of 0.6%, the currently-existing EFs defined for 14 biomes carry important uncertainties and lack the appropriate spatial resolution to capture the effects of terrestrial acidification. In our study, we thus used georeferenced observational data with 113 million data points to develop a comprehensive, global inventory covering 189,185 vascular plant species, which is nearly 100 times more species than existing inventories used in LCIA (raising the species coverage to 49%). EFs were then calculated for 825 ecoregions. Great spatial variability is observed between ecoregions within a same biome spanning up to 3 orders of magnitude, and EFs developed at biome level tend to underestimate acidification effects. We find up to 2 orders of magnitude differences between our EFs and the ones currently recommended for use in LCIA. These results call for updating current LCIA practice to assess acidification impacts with our more differentiated and environmentally representative EFs and to implement our approach to other site-dependent environmental impacts where large georeferenced datasets exist.

Exploring and Illustrating the (Inter-)Disciplinarity of Waste and Zero Waste Management

The aim of this research was to explore the composition, contribution and arrangement of scientific disciplines, across the spectrum from, traditional waste management, to alternative, contemporary approaches, such as the zero waste and circular economy movements. The purpose of this research is to better address the challenge of waste by enhancing the understanding and future employment of interdisciplinary theory and practice. The first outcome of the review strategy employed in this research was to, illustrate a generic rubric of scientific disciplines and to highlight and discuss key disciplines most obviously connected to waste management. This graphic illustration was then overlain with the findings from systematically reviewing a diverse range of indicators and sources of insight and information on the disciplines and interdisciplinarity evident across the spectrum from waste to zero waste management approaches. The resulting final graphic illustrates the intense disciplinarity and hence, the significant interdisciplinary requirement of (zero) waste management. An observation emerging from this research is that, successfully managing the globalised complexity of waste issues and in this, addressing the challenges of climate change and sustainable development, requires cultivating synergy between multiple scientific and practical disciplines. The scope of this challenge increases with the adoption of more holistic, aspirational, countercultural approaches, such as zero waste. It is argued that, enhancing interdisciplinary training and collaboration in research, education and industry/community practice, will improve performance across the spectrum of worldviews, from waste to zero waste.

Linking energy scenarios and waste storylines for prospective environmental assessment of waste management systems

Multiple international and supranational organizations call upon changes in current waste management practices to play a key role in developing more sustainable economies. Life cycle assessment (LCA) is a popular method used to assess the sustainability of future waste management options. The uncertainties about future energy systems and waste compositions, however, may lead to ambiguous LCA results. One way to deal with this challenge is the development of joint energy and waste scenarios to investigate the robustness of waste management options. To date, joint energy and waste scenarios rely on the integration of large economic and engineering models. Complex models can hamper the transparency required for decision-makers to understand and implement LCA recommendations. Here we present the alternative of combining diverse energy scenarios and stakeholder-based waste storylines. This is a more qualitative approach than previous sustainable energy/waste evaluations and has a double aim: to address upfront the energy and waste composition sensitivity and enhance transparency by both relying on well-documented energy scenarios and involving stakeholders in the waste storyline formulation. We apply the approach to the Swiss municipal solid waste (MSW) management system in the context of the energy transition away from nuclear power. Three energy scenarios capture how radical the transition might be, while the storylines reflect societal developments and waste policies leading to low, high, and average MSW amounts. The approach delivers feasibility spaces of energy systems and waste compositions as input to the LCAs. It ensures a high level of transparency, which, in conjunction with the participation of decision-makers, has the potential to increase the chances of implementation of the recommendations based on LCA results.

Modular life cycle assessment of municipal solid waste management

Life cycle assessment (LCA) is commonly applied to examine the environmental performance of waste management systems. The system boundaries are, however, often limited to either one tonne of material or to specific waste treatments and are, therefore, lacking a systems perspective. Here, a framework is proposed to assess complete waste management systems based on actual waste flows, assessed with a detailed material flow analysis (MFA) in a modular MFA/LCA approach. The transformation of the MFA into a product-process-matrix facilitates a direct link between MFA and LCA, therefore allowing for the assessment of variations in flows. To allow for an up-to-date and geographically specific assessment, 190 LCA modules were set up based on primary industrial data and the ecoinvent database. The LCA modules show where there have been improvements in different recycling processes over the past years (e.g. for paper recycling) and highlight that, from an environmental perspective, closed-loop recycling is not always preferable to open-loop recycling. In a case study, the Swiss municipal solid waste management system, of which there is already a detailed MFA, was modeled using the new LCA modules and applying the modular MFA/LCA approach. Five different mass flow distribution scenarios for the Swiss municipal solid waste management system were assessed to show the environmental impact of political measures and to test the sensitivity of the results to key parameters. The results of the case study highlight the importance of the dominant fractions in the overall environmental impacts assessment; while the metal fraction has the highest impact on a per kilogram basis, paper, cardboard, glass and mixed municipal solid waste were found to dominate the environmental impacts of the Swiss waste management system due to their mass. The scenarios also highlight the importance of the energy efficiency of municipal solid waste incineration plants and the credits from material substitution as key variables. In countries with advanced waste management systems such as Switzerland, there is limited improvement potential with further increases in recycling rates. In these cases, the focus of political measures should be laid on (i) the utilization of secondary materials in applications where they replace high-impact primary production, and (ii) an increased recovery of energy in waste-to-energy plants.

Life cycle assessment of thermal waste-to-energy technologies: review and recommendations

Life cycle assessment (LCA) has been used extensively within the recent decade to evaluate the environmental performance of thermal Waste-to-Energy (WtE) technologies: incineration, co-combustion, pyrolysis and gasification. A critical review was carried out involving 250 individual case-studies published in 136 peer-reviewed journal articles within 1995 and 2013. The studies were evaluated with respect to critical aspects such as: (i) goal and scope definitions (e.g. functional units, system boundaries, temporal and geographic scopes), (ii) detailed technology parameters (e.g. related to waste composition, technology, gas cleaning, energy recovery, residue management, and inventory data), and (iii) modeling principles (e.g. energy/mass calculation principles, energy substitution, inclusion of capital goods and uncertainty evaluation). Very few of the published studies provided full and transparent descriptions of all these aspects, in many cases preventing an evaluation of the validity of results, and limiting applicability of data and results in other contexts. The review clearly suggests that the quality of LCA studies of WtE technologies and systems including energy recovery can be significantly improved. Based on the review, a detailed overview of assumptions and modeling choices in existing literature is provided in conjunction with practical recommendations for state-of-the-art LCA of Waste-to-Energy.