Has long-term metal exposure induced changes in life history traits and genetic diversity of the enchytraeid worm Cognettia sphagnetorum (Vejd.)?

We studied whether long-term metal exposure has affected life history traits, population growth patterns and genetic diversity of the asexual enchytraeid worm Cognettia sphagnetorum (Vejd.). Enchytraeids from metal contaminated and uncontaminated forest soil were compared by growing them individually in the laboratory and by following their population development in patchily Cu contaminated microcosms. Genetic differences between the two native populations were studied using allozyme electrophoresis. Individuals from the contaminated site had slower growth rate and they produced fewer fragments of larger size when compared to individuals from the uncontaminated site. In patchily Cu contaminated microcosms, C. sphagnetorum from the contaminated site had a slower population growth rate. Most alleles were shared by the two native populations, but there was greater diversity and more unique genotypes in the population living in the uncontaminated site. Overall, long-term exposure to metals has induced only slight changes in life history properties and clonal diversity of C. sphagnetorum.     

Evaluating Holistic Environmental Consequences of Brownfield Management Options Using Consequential Life Cycle Assessment for Different Perspectives

Brownfields are abandoned, idled, or underused sites whose reuse necessitates some sort of intervention. These sites are largely urban and are frequently contaminated. Brownfield management options can be associated with three types of environmental consequences: those resulting from changes in the site’s environmental quality (primary impacts); those resulting from the actual intervention stage (secondary impacts); and, if the vocation of the site changes, those resulting from effects on regional land use (tertiary impacts). Different stakeholders and decision-making contexts will place a different importance on each of these types of impacts. This article proposes a framework for comparing brownfield management options in regard to these three types of environmental impacts and for interpreting these results from different perspectives. The assessment framework is based on consequential life cycle assessment (LCA), which is shown to provide environmental information on the three types of impacts. The results for a case study are presented, where a “rehabilitation” option allowing residential redevelopment is compared to an “exposure minimization” option not resulting in the site being reused. Calculated primary and tertiary impacts are favorable to the rehabilitation option, whereas secondary impacts are favorable to the exposure minimization option. A ternary diagram presents the favorable option for different stereotypical perspectives. Tertiary impacts are much greater than secondary impacts, and consequently all perspectives that consider tertiary impacts favor rehabilitation. The perspective that considers primary and secondary impacts receives conflicting information. The ternary diagram, showing results for all perspectives, could possibly be useful for consensus-building among stakeholders.     

Life-cycle assessment of two sewage sludge-to-energy systems based on different sewage sludge characteristics: Energy balance and greenhouse gas-emission footprint analysis

Anaerobic digestion and incineration are widely used sewage sludge(SS) treatment and disposal approaches to recovering energy from SS, but it is difficult to select a suitable technical process from the various technologies. In this study, life-cycle assessments were adopted to compare the energy-and greenhouse gas-(GHG) emission footprints of two sludge-to-energy systems. One system uses a combination of AD with incineration(the AI system),whereas the other was simplified by direct incineration...     

Environmental impacts of different food waste resource technologies and the effects of energy mix

The environmental impacts of food waste management strategies and the effects of energy mix were evaluated using a life cycle assessment model, EASEWASTE. Three different strategies involving landfill, composting and combined digestion and composting as core technologies were investigated. The results indicate that the landfilling of food waste has an obvious impact on global warming, although the power recovery from landfill gas counteracts some of this. Food waste composting causes serious acidification (68.0 PE) and nutrient enrichment (76.9 PE) because of NH₃ and SO₂ emissions during decomposition. Using compost on farmland, which can marginally reduce global warming (−1.7 PE), acidification (−0.8 PE), and ecotoxicity and human toxicity through fertilizer substitution, also leads to nutrient enrichment as neutralization of emissions from N loss (27.6 PE) and substitution (−12.8 PE). A combined digestion and composting technology lessens the effects of acidification (−12.2 PE), nutrient enrichment (−5.7 PE), and global warming (−7.9 PE) mainly because energy is recovered efficiently, which decreases emissions including SO₂, Hg, NO_x, and fossil CO₂ during normal energy production. The change of energy mix by introducing more clean energy, which has marginal effects on the performance of composting strategy, results in apparently more loading to acidification and nutrient enrichment in the other two strategies. These are mainly because the recovered energy can avoid fewer emissions than before due to the lower background values in power generation. These results provide quantitative evidence for technical selection and pollution control in food waste management.     

Multi-objective optimization of waste and resource management in industrial networks – Part I: Model description

This article presents a general multi-objective mixed-integer linear programming (MILP) optimization model aimed at providing decision support for waste and resources management in industrial networks. The MILP model combines material flow analysis, process models of waste treatments and other industrial processes, life cycle assessment, and mathematical optimization techniques within a unified framework. The optimization is based on a simplified representation of industrial networks that makes use of linear process models to describe the flows of mass and energy. Waste-specific characteristics, e.g. heating value or heavy metal contamination, are considered explicitly along with potential technologies or process configurations. The systems perspective, including both provision of waste treatment and industrial production, enables constraints imposed upon the systems, e.g. available treatment capacities, to be explicitly considered in the model. The model output is a set of alternative system configurations in terms of distribution of waste and resources that optimize environmental and economic performance. The MILP also enables quantification of the improvement potential compared to a given reference state. Trade-offs between conflicting objectives are identified through the generation of a set of Pareto-efficient solutions. This information supports the decision making process by revealing the quantified performance of the efficient trade-offs without relying on weighting being expressed prior to the analysis. Key features of the modeling approach are illustrated in a hypothetical case. The optimization model described in this article is applied in a subsequent paper (Part II) to assess and optimize the thermal treatment of sewage sludge in a region in Switzerland.     

Based on material flow analysis: Value chain analysis of China iron resources

Iron is an important basic resource for national economic development in China. It is of great strategic importance for the sustainable development of China's economy to study the utilization and circulation status of iron resources. In this paper, using the material flow and value chain analysis method, we quantitatively analyzed the value flow of iron resources in China. According to the value chain and price theory of element M, a value stream diagram of iron resources corresponding to the substance flow chart was plotted. Based on the previous material flow analysis result of iron resources, the diagram quantitatively depicted the value of the circulating flow of iron resources in China in 2011. The results show that by recycling materials, the value of the circulating flow of iron resources can bring considerable economic benefits to both producers and consumers. In the production stage, the expenditures of the entire economic system was reduced by 91.77 billion RMB by circulating iron and the income increased by 95 billion RMB by recycling home scrap, which was generated in the crude steel production stage. In the use stage of iron and steel products, the recycling of old scrap enabled the entire economic system to recover 370.78 billion RMB. It should be noted that analysis within a single framework of physical and economic characteristics of iron resources in the economic system can further extend the research chain of substance flow and value flow at the macro level, enhancing the economic value of substances flow research. In addition, by tracking and depicting the value flow cycle of elements, the improvement potentials and the value situations can be determined to provide useful information for conducting processing and technological innovation for waste minimization.     

Techno-economic analysis and environmental impact assessment of energy recovery from Municipal Solid Waste (MSW) in Brazil

Due to the lack of appropriate policies in the last decades, 60% of Brazilian cities still dump their waste in non-regulated landfills (the remaining ones dump their trash in regulated landfills), which represent a serious environmental and social problem. The key objective of this study is to compare, from a techno-economic and environmental point of view, different alternatives to the energy recovery from the Municipal Solid Waste (MSW) generated in Brazilian cities. The environmental analysis was carried out using current data collected in Betim, a 450,000 inhabitants city that currently produces 200 tonnes of MSW/day. Four scenarios were designed, whose environmental behaviour were studied applying the Life Cycle Assessment (LCA) methodology, in accordance with the ISO 14040 and ISO 14044 standards. The results show the landfill systems as the worst waste management option and that a significant environmental savings is achieved when a wasted energy recovery is done. The best option, which presented the best performance based on considered indicators, is the direct combustion of waste as fuel for electricity generation. The study also includes a techno-economical evaluation of the options, using a developed computer simulation tool. The economic indicators of an MSW energy recovery project were calculated. The selected methodology allows to calculate the energy content of the MSW and the CH₄ generated by the landfill, the costs and incomes associated with the energy recovery, the sales of electricity and carbon credits from the Clean Development Mechanism (CDM). The studies were based on urban centres of 100,000, 500,000 and 1,000,000 inhabitants, using the MSW characteristics of the metropolitan region of Belo Horizonte. Two alternatives to recovering waste energy were analyzed: a landfill that used landfill biogas to generate electricity through generator modules and a Waste-to-Energy (WtE) facility also with electricity generation. The results show that power generation projects using landfill biogas in Brazil strongly depend on the existence of a market for emissions reduction credits. The WtE plant projects, due to its high installation, Operation and Maintenance (O&M) costs, are highly dependent on MSW treatment fees. And they still rely on an increase of three times the city taxes to become attractive.     

Environmental evaluation of plastic waste management scenarios

The management of the plastic fraction is one of the most debated issues in the discussion on integrated municipal solid waste systems. Both material and energy recovery can be performed on such a waste stream, and different separate collection schemes can be implemented. The aim of the paper is to contribute to the debate, based on the analysis of different plastic waste recovery routes. Five scenarios were defined and modelled with a life cycle assessment approach using the EASEWASTE model. In the baseline scenario (P0) the plastic is treated as residual waste and routed partly to incineration with energy recovery and partly to mechanical biological treatment. A range of potential improvements in plastic management is introduced in the other four scenarios (P1–P4). P1 includes a source separation of clean plastic fractions for material recycling, whereas P2 a source separation of mixed plastic fraction for mechanical upgrading and separation into specific polymer types, with the residual plastic fraction being down-cycled and used for “wood items”. In P3 a mixed plastic fraction is source separated together with metals in a “dry bin”. In P4 plastic is mechanically separated from residual waste prior to incineration.A sensitivity analysis on the marginal energy was carried out. Scenarios were modelled as a first step assuming that marginal electricity and heat were based on coal and on a mix of fuels and then, in the sensitivity analysis, the marginal energy was based on natural gas.The study confirmed the difficulty to clearly identify an optimal strategy for plastic waste management. In fact none of the examined scenarios emerged univocally as the best option for all impact categories. When moving from the P0 treatment strategy to the other scenarios, substantial improvements can be obtained for “Global Warming”. For the other impact categories, results are affected by the assumption about the substituted marginal energy. Nevertheless, irrespective of the assumptions on marginal energy, scenario P4, which implies the highest quantities of specific polymer types sent to recycling, resulted the best option in most impact categories.