An energetic life cycle assessment of C&D waste and container glass recycling in Cape Town, South Africa

The body of life cycle assessment (LCA) literature is vast and has grown over the last decade at a dauntingly rapid rate. Many LCAs have been published on the same or very similar technologies or products, in some cases leading to hundreds of publications. One result is the impression among decision makers that LCAs are inconclusive, owing to perceived and real variability in published estimates of life cycle impacts. Despite the extensive available literature and policy need formore conclusive assessments, only modest attempts have been made to synthesize previous research. A significant challenge to doing so are differences in characteristics of the considered technologies and inconsistencies in methodological choices (e.g., system boundaries, coproduct allocation, and impact assessment methods) among the studies that hamper easy comparisons and related decision support. An emerging trend is meta-analysis of a set of results from LCAs, which has the potential to clarify the impacts of a particular technology, process, product, or material and produce more robust and policy-relevant results. Meta-analysis in this context is defined here as an analysis of a set of published LCA results to estimate a single or multiple impacts for a single technology or a technology category, either in a statisticalmore » sense (e.g., following the practice in the biomedical sciences) or by quantitative adjustment of the underlying studies to make them more methodologically consistent. One example of the latter approach was published in Science by Farrell and colleagues (2006) clarifying the net energy and greenhouse gas (GHG) emissions of ethanol, in which adjustments included the addition of coproduct credit, the addition and subtraction of processes within the system boundary, and a reconciliation of differences in the definition of net energy metrics. Such adjustments therefore provide an even playing field on which all studies can be considered and at the same time specify the conditions of the playing field itself. Understanding the conditions under which a meta-analysis was conducted is important for proper interpretation of both the magnitude and variability in results. This special supplemental issue of the Journal of Industrial Ecology includes 12 high-quality metaanalyses and critical reviews of LCAs that advance understanding of the life cycle environmental impacts of different technologies, processes, products, and materials. Also published are three contributions on methodology and related discussions of the role of meta-analysis in LCA. The goal of this special supplemental issue is to contribute to the state of the science in LCA beyond the core practice of producing independent studies on specific products or technologies by highlighting the ability of meta-analysis of LCAs to advance understanding in areas of extensive existing literature. The inspiration for the issue came from a series of meta-analyses of life cycle GHG emissions from electricity generation technologies based on research from the LCA Harmonization Project of the National Renewable Energy Laboratory (NREL), a laboratory of the U.S. Department of Energy, which also provided financial support for this special supplemental issue. (See the editorial from this special supplemental issue [Lifset 2012], which introduces this supplemental issue and discusses the origins, funding, peer review, and other aspects.) The first article on reporting considerations for meta-analyses/critical reviews for LCA is from Heath and Mann (2012), who describe the methods used and experience gained in NREL's LCA Harmonization Project, which produced six of the studies in this special supplemental issue. Their harmonization approach adapts key features of systematic review to identify and screen published LCAs followed by a meta-analytical procedure to adjust published estimates to ones based on a consistent set of methods and assumptions to allow interstudy comparisons and conclusions to be made. In a second study on methods, Zumsteg and colleagues (2012) propose a checklist for a standardized technique to assist in conducting and reporting systematic reviews of LCAs, including meta-analysis, that is based on a framework used in evidence-based medicine. Widespread use of such a checklist would facilitate planning successful reviews, improve the ability to identify systematic reviews in literature searches, ease the ability to update content in future reviews, and allow more transparency of methods to ease peer review and more appropriately generalize findings. Finally, Zamagni and colleagues (2012) propose an approach, inspired by a meta-analysis, for categorizing main methodological topics, reconciling diverging methodological developments, and identifying future research directions in LCA. Their procedure involves the carrying out of a literature review on articles selected according to predefined criteria.« less

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third

Despite the ever-growing body of life cycle assessment (LCA) literature on electricity generation technologies, inconsistent methods and assumptions hamper comparison across studies and pooling of published results. Synthesis of the body of previous research is necessary to generate robust results to assess and compare environmental performance of different energy technologies for the benefit of policy makers, managers, investors, and citizens. With funding from the U.S. Department of Energy, the National Renewable Energy Laboratory initiated the LCA Harmonization Project in an effort to rigorously leverage the numerous individual studies to develop collective insights. The goals of this project were to: (1) understand the range of published results of LCAs of electricity generation technologies, (2) reduce the variability in published results that stem from inconsistent methods and assumptions, and (3) clarify the central tendency of published estimates to make the collective results of LCAs available to decision makers in the near term. The LCA Harmonization Project's initial focus was evaluating life cycle greenhouse gas (GHG) emissions from electricity generation technologies. Six articles from this first phase of the project are presented in a special supplemental issue of the Journal of Industrial Ecology on Meta-Analysis of LCA: coal (Whitaker et al. 2012), concentratingmore » solar power (Burkhardt et al. 2012), crystalline silicon photovoltaics (PVs) (Hsu et al. 2012), thin-film PVs (Kim et al. 2012), nuclear (Warner and Heath 2012), and wind (Dolan and Heath 2012). Harmonization is a meta-analytical approach that addresses inconsistency in methods and assumptions of previously published life cycle impact estimates. It has been applied in a rigorous manner to estimates of life cycle GHG emissions from many categories of electricity generation technologies in articles that appear in this special supplemental supplemental issue, reducing the variability and clarifying the central tendency of those estimates in ways useful for decision makers and analysts. Each article took a slightly different approach, demonstrating the flexibility of the harmonization approach. Each article also discusses limitations of the current research, and the state of knowledge and of harmonization, pointing toward a path of extending and improving the meta-analysis of LCAs.« less

Carbon-neutral building renovation potential with passive house-certified components: Applications for an exemplary apartment building in the Republic of Korea

Addressing the social life cycle inventory analysis data gap: Insights from a case study of cobalt mining in the Democratic Republic of the Congo

Who Cares About Life Cycle Assessment?

A life cycle assessment (LCA) approach was used to examine the greenhouse gas (GHG) emissions and energy balance of short rotation coppice (SRC) willow for heat production. The modelled supply chain includes cutting multiplication, site establishment, maintenance, harvesting, storage, transport and combustion. The relative impacts of dry matter losses and methane emissions from chip storage were examined from a LCA perspective, comparing the GHG emissions from the SRC supply chain with those of natural gas for heat generation. The results show that SRC generally provides very high GHG emission savings of over 90 %. The LCA model estimates that a 1, 10 and 20 % loss of dry matter during storage causes a 1, 6 and 11 % increase in GHG emissions per MWh. The GHG emission results are extremely sensitive to emissions of methane from the wood chip stack: If 1 % of the carbon within the stack undergoes anaerobic decomposition to methane, then the GHG emissions per MWh are tripled. There are some uncertainties in the LCA results, regarding the true formation of methane in wood chip stacks, non-CO2 emissions from combustion, N2O emissions from leaf fall and the extent of carbon sequestered under the crop, and these all contribute a large proportion of the life cycle GHG emissions from cultivation of the crop.

Feeding a growing, increasingly affluent population while limiting environmental pressures of food production is a central challenge for society. Understanding the location and magnitude of food production is key to addressing this challenge because pressures vary substantially across food production types. Applying data and models from life cycle assessment with the methodologies for mapping cumulative environmental impacts of human activities (hereafter cumulative impact mapping) provides a powerful approach to spatially map the cumulative environmental pressure of food production in a way that is consistent and comprehensive across food types. However, these methodologies have yet to be combined. By synthesizing life cycle assessment and cumulative impact mapping methodologies, we provide guidance for comprehensively and cumulatively mapping the environmental pressures (e.g., greenhouse gas emissions, spatial occupancy, and freshwater use) associated with food production systems. This spatial approach enables quantification of current and potential future environmental pressures, which is needed for decision makers to create more sustainable food policies and practices.

Understanding the Climate Mitigation Benefits of Product Systems: Comment on “Using Attributional Life Cycle Assessment to Estimate Climate‐Change Mitigation…”

Assessing the greenhouse gas mitigation potential of urban precincts with hybrid life cycle assessment

A feasibility study of microgrids for reducing energy use and GHG emissions in an industrial application

Global warming potential (GWP) has been widely used in the life cycle assessment (LCA) to quantify the climate impacts of energy technologies. Most LCAs are static analyses without considering the dynamics of greenhouse gas (GHG) emissions and changes in background GHG concentrations. This study presents a dynamic approach to analyze the life-cycle GWP of energy technologies in different timeframes and representative GHG concentration pathways. Results show that higher atmospheric GHG concentrations lead to higher life-cycle GWP for long-term analysis. The impacts of background GHG concentrations are more significant for technologies with large operational emissions or CH4 emissions than technologies with low operational emissions. The case study for the U.S. electricity sector in 2020-2050 shows the impacts of background GHG concentrations and different LCA methods on estimating national climate impacts of different energy technology scenarios. Based on the results, it is recommended for future LCAs to incorporate temporal effects of GHG emissions when (1) the technology has large operational GHG emissions or CH4 emissions; (2) the analysis time frame is longer than 50 years; (3) when LCA results are used for policymaking or technology comparisons for mitigating climate change.

Life Cycle Assessment of fossil energy use and greenhouse gas emissions in Chinese pear production

Circular utilization of urban tree waste contributes to the mitigation of climate change and eutrophication

Livestock production is indicated to be one of the major emitters of greenhouse gases (GHG), particularly methane (CH4) and nitrous oxide (N2O), around the globe, and the reduction of these emissions is an important goal. GHG emissions as well as other environmental impacts of two pig (Sus scrofa domesticus) farming systems, one using conventional diets (CNV) and the other using low-protein diets supplemented with crystalline amino acids (LOW), were therefore evaluated by comparative life cycle assessment (LCA) focusing on manure management and by cradle-to-farm gate LCA. The functional unit was defined as one marketed pig. For the comparative LCA of manure management, the CH4 and N2O emissions from manure management of CNV were set as a baseline, and the system boundary of LOW included the CH4 and N2O emissions from manure management, and changes in the GHG emissions from feed production including amino acid manufacturing, feed transport, and the materials and energy consumed in manure management. For the cradle-to-farm gate LCA of pig farming, the evaluated system included the processes of feed production including amino acid manufacturing for LOW, feed transport, animal housing including the biological activity of the animal, and manure management. The results of the comparative LCA showed that the GHG emissions from manure management of LOW were 20% less than those of CNV, and the GHG reduction rate of LOW compared to CNV was even greater in the case of a stricter target of effluent nitrogen content. The results of cradle-to-farm gate LCA showed that LOW had lower GHG emissions, acidification potential, eutrophication potential and overall environmental impact, and slightly larger energy consumption, than CNV. The sensitivity analysis showed that LOW still had less GHG emissions than CNV, even in the least preferable case assuming a 40% lower reduction rate of nitrogen excretion.