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.

Is there an environmentally optimal separate collection rate?

Material recycling often leads to environmental benefits when compared to thermal treatments or landfilling and is therefore positioned in the waste hierarchy as the third priority after waste prevention and reuse. To assess the environmental impacts of recycling and the related substitution of primary material, linear steady-state models of physical flows are typically used. In reality, the environmental burdens of collection and recycling are likely to be a non-linear function of the collection rate. This short communication aims at raising awareness of the non-linear effects in separate collection systems and presents the first non-linear quantitative model for PET bottle recycling. The influence of collection rates on the material quality and the transport network is analyzed based on the data collected from industrial partners. The results highlight that in the present Swiss recycling system a very high collection rate close to 100% yields optimum environmental benefits with respect to global warming. The empirical data, however, provided indications for a decrease in the marginal environmental benefit of recycling. This can be seen as an indication that tipping points may exist for other recycling systems, in which the environmental benefits from substituting primary materials are less pronounced than they are for PET.

Cumulative exergy extraction from the natural environment (CEENE): a comprehensive life cycle impact assessment method for resource accounting.

The objective of the paper is to establish a comprehensive resource-based life cycle impact assessment (LCIA) method which is scientifically sound and that enables to assess all kinds of resources that are deprived from the natural ecosystem, all quantified on one single scale, free of weighting factors. The method is based on the exergy concept. Consistent exergy data on fossils, nuclear and metal ores, minerals, air, water, land occupation, and renewable energy sources were elaborated, with well defined system boundaries. Based on these data, the method quantifies the exergy "taken away" from natural ecosystems, and is thus called the cumulative exergy extraction from the natural environment (CEENE). The acquired data set was coupled with a state-of-the art life cycle inventory database, ecoinvent. In this way, the method is able to quantitatively distinguish eight categories of resources withdrawn from the natural environment: renewable resources, fossil fuels, nuclear energy, metal ores, minerals, water resources, land resources, and atmospheric resources. Third, the CEENE method is illustrated for a number of products that are available in ecoinvent, and results are compared with common resource oriented LCIA methods. The application to the materials in the ecoinvent database showed that fossil resources and land use are of particular importance with regard to the total CEENE score, although the other resource categories may also be significant.

[Epiduroscopy with access via the sacral canal. Some constructional equipment requirements from the anatomic and biomechanical viewpoint]. / Epiduroskopie mit Zugang über den Sakralkanal. Einige konstruktive Anforderungen an Instrumente aus anatomischer und biomechanischer Sicht.

To ensure optimal mechanical functioning of the vertebral column, intact symmetry of its bony and muscular elements is mandatory. With this in mind, the need to reduce the invasiveness of spinal surgery is even greater than that applying to surgery in general. To avoid bony or muscular damage during surgery, in particular in the case of the segments L4/L5 and L5/S1-which are particularly prone to intervertebral disc rupture-laser discotomy procedures, with introduction of instruments via the sacral canal during epiduroscopy are presently being developed. Preliminary experiments on human corpses have demonstrated the practicability of the technique, but specially designed instruments have yet to be developed for use in patients. In an attempt to define the conditions of important for the design of the instrument, we have carried out a morphometric analysis of 100 sacral bones (56 females; 44 males). The configuration of the sacral canal is described in quantitative terms, and the results used to determine the diameters and curvatures of the instruments needed for laser discotomy.