A Methodology for Robust Comparative Life Cycle Assessments Incorporating Uncertainty.

We propose a methodology for conducting robust comparative life cycle assessments (LCA) by leveraging uncertainty. The method evaluates a broad range of the possible scenario space in a probabilistic fashion while simultaneously considering uncertainty in input data. The method is intended to ascertain which scenarios have a definitive environmentally preferable choice among the alternatives being compared and the significance of the differences given uncertainty in the parameters, which parameters have the most influence on this difference, and how we can identify the resolvable scenarios (where one alternative in the comparison has a clearly lower environmental impact). This is accomplished via an aggregated probabilistic scenario-aware analysis, followed by an assessment of which scenarios have resolvable alternatives. Decision-tree partitioning algorithms are used to isolate meaningful scenario groups. In instances where the alternatives cannot be resolved for scenarios of interest, influential parameters are identified using sensitivity analysis. If those parameters can be refined, the process can be iterated using the refined parameters. We also present definitions of uncertainty quantities that have not been applied in the field of LCA and approaches for characterizing uncertainty in those quantities. We then demonstrate the methodology through a case study of pavements.

Evaluating the economic viability of a material recovery system: the case of cathode ray tube glass.

This paper presents an analysis of the material recovery system for leaded glass from cathode ray tubes (CRTs) using a dynamic material flow analysis. In particular, the global mass flow of primary and secondary CRT glass and the theoretical capacities for using secondary CRT glass to make new CRT glass are analyzed. The global mass flow analysis indicates that the amount of new glass required is decreasing, but is much greater than the amount of secondary glass collected, which is increasing. The comparison of the ratio of secondary glass collected to the amount of new glass required from the mass flow analysis indicates that the material recovery system is sustainable for the foreseeable future. However, a prediction of the time at which the market for secondary glass will collapse due to excess capacity is not possible at the moment due to several sources of uncertainty.

A framework for evaluating the economic performance of recycling systems: a case study of North American electronics recycling systems.

A framework for evaluating the economic performance of a recycling system is proposed, and data from four electronics recycling systems in North America (Alberta, California, Maine, and Maryland) that use different operating models are used as a preliminary test of the framework. The framework is built around a hierarchy of descriptors that clarify the function of the system components under consideration and the activities, cash flow elements, and resources within those functions; costs are incurred by specific stakeholders. Data from each system on fee and mass collection amounts and collection, processing, and management costs are used to create a matrix of several net costs for stakeholders within each system. Although all four systems are relatively new, thereby making data collection a challenge, some preliminary insights can be gleaned from comparing the systems. Processing costs vary significantly in the four systems, with Alberta and California having the highest reimbursement rates for processing. Alberta and California also have relatively high system management costs, but processors are generally quite satisfied with the systems. Maine has an additional cost for consolidation that is an implicit management cost because of the need to count incoming products by manufacturer.