Dominik Saner

Persistence of engineered nanoparticles in a municipal solid-waste incineration plant

More than 100 million tonnes of municipal solid waste are incinerated worldwide every year. However, little is known about the fate of nanomaterials during incineration, even though the presence of engineered nanoparticles in waste is expected to grow. Here, we show that cerium oxide nanoparticles introduced into a full-scale waste incineration plant bind loosely to solid residues from the combustion process and can be efficiently removed from flue gas using current filter technology. The nanoparticles were introduced either directly onto the waste before incineration or into the gas stream exiting the furnace of an incinerator that processes 200,000 tonnes of waste per year. Nanoparticles that attached to the surface of the solid residues did not become a fixed part of the residues and did not demonstrate any physical or chemical changes. Our observations show that although it is possible to incinerate waste without releasing nanoparticles into the atmosphere, the residues to which they bind eventually end up in landfills or recovered raw materials, confirming that there is a clear environmental need to develop degradable nanoparticles.

An LCA model for waste incineration enhanced with new technologies for metal recovery and application to the case of Switzerland

A process model of municipal solid waste incinerators (MSWIs) and new technologies for metal recovery from combustion residues was developed. The environmental impact is modeled as a function of waste composition as well as waste treatment and material recovery technologies. The model includes combustion with a grate incinerator, several flue gas treatment technologies, electricity and steam production from waste heat recovery, metal recovery from slag and fly ash, and landfilling of residues and can be tailored to specific plants and sites (software tools can be downloaded free of charge). Application of the model to Switzerland shows that the treatment of one tonne of municipal solid waste results on average in 425 kg CO2-eq. generated in the incineration process, and 54 kg CO2-eq. accrue in upstream processes such as waste transport and the production of operating materials. Downstream processes, i.e. residue disposal, generates 5 kg CO2-eq. Savings from energy recovery are in the range of 67 to 752 kg CO2-eq. depending on the assumptions regarding the substituted energy production, while the recovery of metals from slag and fly ash currently results in a net saving of approximately 35 kg CO2-eq. A similar impact pattern is observed when assessing the MSWI model for aggregated environmental impacts (ReCiPe) and for non-renewable resource consumption (cumulative exergy demand), except that direct emissions have less and no relevance, respectively, on the total score. The study illustrates that MSWI plants can be an important element of industrial ecology as they provide waste disposal services and can help to close material and energetic cycles.

Effects of consumptive water use on biodiversity in wetlands of international importance.

Wetlands are complex ecosystems that harbor a large diversity of species. Wetlands are among the most threatened ecosystems on our planet, due to human influences such as conversion and drainage. We assessed impacts from water consumption on the species richness of waterbirds, nonresidential birds, water-dependent mammals, reptiles and amphibians in wetlands, considering a larger number of taxa than previous life cycle impact assessment methods. Effect factors (EF) were derived for 1184 wetlands of international importance. EFs quantify the number of global species-equivalents lost per m2 of wetland area loss. Vulnerability and range size of species were included to reflect conservation values. Further, we derived spatially explicit characterization factors (CFs) that distinguish between surface water and groundwater consumption. All relevant watershed areas that are contributing to feeding the respective wetlands were determined for CF applications. In an example of rose production, we compared damages of water consumption in Kenya and The Netherlands. In both cases, the impact was largest for waterbirds. The total impact from water consumption in Kenya was 67 times larger than in The Netherlands, due to larger species richness and species’ vulnerability in Kenya, as well as more arid conditions and larger amounts of water consumed.

Probabilistic and Technology-Specific Modeling of Emissions from Municipal Solid-Waste Incineration

The European legislation increasingly directs waste streams which cannot be recycled toward thermal treatment. Models are therefore needed that help to quantify emissions of waste incineration and thus reveal potential risks and mitigation needs. This study presents a probabilistic model which computes emissions as a function of waste composition and technological layout of grate incineration plants and their pollution-control equipment. In contrast to previous waste-incineration models, this tool is based on a broader empirical database and allows uncertainties in emission loads to be quantified. Comparison to monitoring data of 83 actual European plants showed no significant difference between modeled emissions and measured data. An inventory of all European grate incineration plants including technical characteristics and plant capacities was established, and waste material mixtures were determined for different European countries, including generic elemental waste-material compositions. The model thus allows for calculation of country-specific and material-dependent emission factors and enables identification and tracking of emission sources. It thereby helps to develop strategies to decrease plant emissions by reducing or redirecting problematic waste fractions to other treatment options or adapting the technological equipment of waste incinerators.

Regionalized LCA-Based Optimization of Building Energy Supply: Method and Case Study for a Swiss Municipality

This paper presents a regionalized LCA-based multiobjective optimization model of building energy demand and supply for the case of a Swiss municipality for the minimization of greenhouse gas emissions and particulate matter formation. The results show that the environmental improvement potential is very large: in the optimal case, greenhouse gas emissions from energy supply could be reduced by more than 75% and particulate emissions by over 50% in the municipality. This scenario supposes a drastic shift of heat supply systems from a fossil fuel dominated portfolio to a portfolio consisting of mainly heat pump and woodchip incineration systems. In addition to a change in heat supply technologies, roofs, windows and walls would need to be refurbished in more than 65% of the municipalitys buildings. The full potential of the environmental impact reductions will hardly be achieved in reality, particularly in the short term, for example, because of financial constraints and social acceptance, which were not taken into account in this study. Nevertheless, the results of the optimization model can help policy makers to identify the most effective measures for improvement at the decision making level, for example, at the building level for refurbishment and selection of heating systems or at the municipal level for designing district heating networks. Therefore, this work represents a starting point for designing effective incentives to reduce the environmental impact of buildings. While the results of the optimization model are specific to the municipality studied, the model could readily be adapted to other regions.

Housing and Mobility Demands of Individual Households and their Life Cycle Assessment

Household consumption, apart from governmental consumption, is the main driver of worldwide economy. Attached to each household purchase are economic activities along the preceding supply chain, with the associated resource use and emissions. A method to capture and assess all these resource uses and emissions is life cycle assessment. We developed a model for the life cycle assessment of housing and land-based mobility (excluding air travel) consumption of individual households a small village in Switzerland. Statistical census and dwelling register data are the foundations of the model. In a case study performed on a midsized community, we found a median value of greenhouse gas emissions of 3.12 t CO2 equiv and a mean value of 4.30 t CO2 equiv per capita and year for housing and mobility. Twenty-one percent of the households in the investigated region were responsible for 50% of the total greenhouse gas emissions, meaning that if their emissions could be halved the total emissions of the community would be reduced by 25%. Furthermore, a cluster analysis revealed that driving factors for large environmental footprints are demands of large living area heated by fossil energy carriers, as well as large demands of motorized private transportation.

End-of-life and waste management in life cycle assessment—Zurich, 6 December 2011

IntroductionWaste management is a key component in societys strategy to mitigate the adverse effects of its economic activities. Through its comprehensive system approach, life cycle assessment (LCA) is frequently put forward as a powerful tool for the assessment of waste management activities. However, many methodological challenges regarding the environmental assessment of waste treatment systems still remain, and consensus is still far from being reached in areas like the definition of (temporal) system boundaries, life cycle inventory generation, selection and use of environmental indicators, and interpretation and communication of the LCA results.Summary of the topics presented in DF-46The 46th Swiss Discussion Forum on Life Cycle Assessment (DF-46) consisted of three sessions. The first session tried to address policy making and implications for sustainable waste management of consumer products, e.g., information and communication technology, and food packaging. The second session focused on recent methodological developments in LCA for end-of-life treatment (EoL) activities and waste management assessment. The third session was dedicated to E-waste treatment and scarce metal recovery processes. DF-46 closed with short presentations on decision support in the areas of coprocessing, food waste, and after-treatment technologies for municipal waste incineration residues.ConclusionsThe main conclusions drawn from DF-46 are: (a) the option of waste prevention, despite its prominent position in the so-called waste hierarchy, is rarely considered in LCAs on waste and EoL management, (b) although a general problem in many other applications of LCA, the differences in scope definitions and time perspectives, the use of proxies or data of poor quality, allocation, or system expansion procedures, and weighting in the impact assessment are prominent issues in LCAs of waste and EoL management and thus have to be minimized and inventory data must be as transparent as possible, (c) life cycle inventory formats have to be adapted to be able to account for new materials, such as nanoparticles and scarce metals in LCA, (d) the selection of environmental indicators requires clear guidance on their appropriate use and open communication. The selection of a set of complementary indicators is of particular importance in order to avoid that the adverse effects on the environment are merely shifted between impact categories, and (e) useful LCA tools for the environmental assessment of waste management options are currently developed to meet the evolving demands and expectations for support in decision making related to waste and EoL management today and in the future. The presentations from DF-46 are available for download (www.lcaforum.ch).