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Graham Treloar - One of the best experts on this subject based on the ideXlab platform.
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System Boundary selection in life cycle inventories using hybrid approaches
Environmental Science & Technology, 2004Co-Authors: Sangwon Suh, Arpad Horvath, Graham Treloar, Manfred Lenzen, Hiroki Hondo, Gjalt Huppes, Olivier Jolliet, Uwe Klann, Wolfram Krewitt, Yuichi MoriguchiAbstract:Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing System boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input-output analysis have shown that, in practice, excluded processes can contribute as much to the product System under study as included processes; thus, the subjective determination of the System Boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the Boundary selection problem in LCA. An input-output model can be used to describe at least a part of a product System, and an ISO-compatible System Boundary selection procedure can be designed by applying hybrid input-output-assisted approaches. There are several hybrid input-output analysis-based LCA methods that can be implemented in practice for broadening System Boundary and also for ISO compliance.
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life cycle energy analysis of buildings a case study
Building Research and Information, 2000Co-Authors: Graham Treloar, Usha IyerranigaAbstract:Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as life-cycle energy analysis. With Kyoto target obligations necessitating the quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. If conducted in primary energy terms, such analyses directly reflect greenhouse gas emissions, except for a few processes which involve significant non-energy related emissions such as cement manufacture. A Life-Cycle Assessment would include these issues, as well as other environmental parameters, though probably with a corresponding decrease in System Boundary completeness. This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Australian based case s...
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extracting embodied energy paths from input output tables towards an input output based hybrid energy analysis method
Economic Systems Research, 1997Co-Authors: Graham TreloarAbstract:Embodied energy is defined as the energy consumed in all activities necessary to support a process, including upstream processes. The Leontief inverse input–output (IO) matrix gives results that are practically complete, because of the aggregation of direct and indirect requirements, but which are also unreliable, because of inherent assumptions. Although accurate for the System Boundary considered, process analysis results are incomplete relative to the pure IO System Boundary. Attempts to combine process and IO analysis tend to be based on process analysis data. The System Boundary is still significantly incomplete—although not as incomplete as for pure process analysis. An IO-based hybrid analysis technique that requires the extraction of particular paths from the direct IO matrix has been developed. The potential for embodied energy paths to be used as the basis for a hybrid analysis of the Australian residential building sector is discussed. The results indicate that less than three-quarters of the t...
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extracting embodied energy paths from input output tables towards an input output based hybrid energy analysis method
Economic Systems Research, 1997Co-Authors: Graham TreloarAbstract:Embodied energy is defined as the energy consumed in all activities necessary to support a process, including upstream processes. The Leontief inverse input-output (IO) matrix gives results that are practically complete, because of the aggregation of direct and indirect requirements, but which are also unreliable, because of inherent assumptions. Although accurate for the System Boundary considered, process analysis results are incomplete relative to the pure IO System Boundary. Attempts to combine process and IO analysis tend to be based on process analysis data. The System Boundary is still significantly incomplete—although not as incomplete as for pure process analysis. An IO-based hybrid analysis technique that requires the extraction of particular paths from the direct IO matrix has been developed. The potential for embodied energy paths to be used as the basis for a hybrid analysis of the Australian residential building sector is discussed. The results indicate that less than three-quarters of the total embodied energy of this sector is likely to be able to be validated, because of the complexity of the embodied energy paths.
Reinout Heijungs - One of the best experts on this subject based on the ideXlab platform.
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moving from completing System boundaries to more realistic modeling of the economy in life cycle assessment
International Journal of Life Cycle Assessment, 2019Co-Authors: Yi Yang, Reinout HeijungsAbstract:Existing process-based life cycle assessment (LCA) models can be supplemented by input-output (IO) models to correct for the so-called truncation error resulting from an “incomplete” System Boundary. The resulting hybrid LCA is not necessarily but probably a closer approximation to an ideally complete process model with a global all-inclusive System Boundary. Here, we discuss whether such a complete process model is a goal worth pursuing and whether System Boundary is the main limitation of process-based LCA. We argue that the results of the ideally complete process model, with every single economic activity on earth embodied within, have little to limited implications and relevance for the decisions which LCA seeks to support and which involve changes aimed at reducing environmental impacts through altering product Systems or promoting alternatives. The main limitations of process-based LCA, as a supply chain based linear model, lie not in the “incomplete” System Boundary but in the narrow focus on supply chain and the unrealistic assumptions, such as omission of price effects and constraints. These assumptions reflect poorly how the economy works. Hybrid LCA, through adding IO models, which are also supply chain and linearity based, doubles down on both the narrow focus on supply chain and the unrealistic assumptions, and thus is a step forward but in the wrong direction. Reflecting on advances in corn ethanol research, we show that pursuing a more complete System Boundary by, for instance, covering Chinese stuffed animal production does not make the LCA results more accurate or relevant for determining if corn ethanol in the US should be promoted. Not only is the theoretical argument for including Chinese stuffed animal industry tenuous, but there is no evidence it has been affected by US corn ethanol expansion. And by worrying about processes far away up the supply chain could distract us from focusing on the actual market mechanisms, such as indirect land use change, that are more likely to occur and are essential to predicting whether promoting corn ethanol would reduce total carbon emissions. We suggest future studies shifting focus from “completing” System Boundary within the conventional supply chain and linear framework towards more realistic modeling of our complicated human-environment System. Instead of trying to always include everything, we argue for a flexible and market-based System Boundary tailored to the decision in question, particularly considering the scale of potential changes it may cause and how it may affect the economy. A change at larger scales is likely to have a broader impact, thus justifying the definition of a broader System Boundary. But to cover a broad System Boundary for a small change will likely result in overestimates. More is not necessarily better.
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hybrid life cycle assessment lca does not necessarily yield more accurate results than process based lca
Journal of Cleaner Production, 2017Co-Authors: Yi Yang, Reinout Heijungs, Miguel BrandaoAbstract:Hybrid life cycle assessment (LCA), through combining input-output (IO) models and process-based LCA for a complete System Boundary, is widely recognized as a more accurate approach than process-based LCA with an incomplete System Boundary. Without a complete process model for verification, however, the performance of hybrid LCA remains unclear. Here, using a counterexample we show that hybrid LCA does not necessarily provide more accurate results than process-based LCA, simply because the aggregation of heterogeneous processes in IO models may introduce more errors. In so doing, we prove that only when IO-based LCA and process-based LCA have the same level of detail would they yield the same results. Whether hybrid LCA provides more accurate estimates depends on whether the IO model introduced serves as an adequate proxy for the missing products as opposed to if they were estimated by a complete process model. The use of a highly-aggregated IO model runs the risk of overestimation, and could result in a larger relative error than the truncation error resulting from an incomplete process model. Our study seeks to provide a balanced view of hybrid LCA, and our findings offer important insights for future hybrid LCA studies to improve the accuracy and realm of applicability of the approach.
Thomas Hojlund Christensen - One of the best experts on this subject based on the ideXlab platform.
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c balance carbon dioxide emissions and global warming potentials in lca modelling of waste management Systems
Waste Management & Research, 2009Co-Authors: Thomas Hojlund Christensen, Anna Warberg Larsen, Bo Pedersen Weidema, Emmanuel Gentil, Alessio Boldrin, Michael Zwicky HauschildAbstract:Global warming potential (GWP) is an important impact category in life-cycle-assessment modelling of waste management Systems. However, accounting of biogenic CO2 emissions and sequestered biogenic carbon in landfills and in soils, amended with compost, is carried out in different ways in reported studies. A simplified model of carbon flows is presented for the waste management System and the surrounding industries, represented by the pulp and paper manufacturing industry, the forestry industry and the energy industry. The model calculated the load of C to the atmosphere, under ideal conditions, for 14 different waste management scenarios under a range of System Boundary conditions and a constant consumption of C-product (here assumed to be paper) and energy production within the combined System. Five sets of criteria for assigning GWP indices to waste management Systems were applied to the same 14 scenarios and tested for their ability to rank the waste management alternatives reflecting the resulting CO...
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life cycle assessment of waste paper management the importance of technology data and System boundaries in assessing recycling and incineration
Resources Conservation and Recycling, 2008Co-Authors: Hanna Kristina Merrild, Anders Damgaard, Thomas Hojlund ChristensenAbstract:The significance of technical data, as well as the significance of System Boundary choices, when modelling the environmental impact from recycling and incineration of waste paper has been studied by a life cycle assessment focusing on global warming potentials. The consequence of choosing a specific set of data for the reprocessing technology, the virgin paper manufacturing technology and the incineration technology, as well as the importance of the recycling rate was studied. Furthermore, the System was expanded to include forestry and to include fossil fuel energy substitution from saved biomass, in order to study the importance of the System Boundary choices. For recycling, the choice of virgin paper manufacturing data is most important, but the results show that also the impacts from the reprocessing technologies fluctuate greatly. For the overall results the choice of the technology data is of importance when comparing recycling including virgin paper substitution with incineration including energy substitution. Combining an environmentally high or low performing recycling technology with an environmentally high or low performing incineration technology can give quite different results. The modelling showed that recycling of paper, from a life cycle point of view, is environmentally equal or better than incineration with energy recovery only when the recycling technology is at a high environmental performance level. However, the modelling also showed that expanding the System to include substitution of fossil fuel energy by production of energy from the saved biomass associated with recycling will give a completely different result. In this case recycling is always more beneficial than incineration, thus increased recycling is desirable. Expanding the System to include forestry was shown to have a minor effect on the results. As assessments are often performed with a set choice of data and a set recycling rate, it is questionable how useful the results from this kind of LCA are for a policy maker. The high significance of the System Boundary choices stresses the importance of scientific discussion on how to best address System analysis of recycling, for paper and other recyclable materials.
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life cycle assessment of waste paper management the importance of technology data and System boundaries in assessing recycling and incineration
Resources Conservation and Recycling, 2008Co-Authors: Hanna Kristina Merrild, Anders Damgaard, Thomas Hojlund ChristensenAbstract:The significance of technical data, as well as the significance of System Boundary choices, when modelling the environmental impact from recycling and incineration of waste paper has been studied by a life cycle assessment focusing on global warming potentials. The consequence of choosing a specific set of data for the reprocessing technology, the virgin paper manufacturing technology and the incineration technology, as well as the importance of the recycling rate was studied. Furthermore, the System was expanded to include forestry and to include fossil fuel energy substitution from saved biomass, in order to study the importance of the System Boundary choices. For recycling, the choice of virgin paper manufacturing data is most important, but the results show that also the impacts from the reprocessing technologies fluctuate greatly. For the overall results the choice of the technology data is of importance when comparing recycling including virgin paper substitution with incineration including energy substitution. Combining an environmentally high or low performing recycling technology with an environmentally high or low performing incineration technology can give quite different results. The modelling showed that recycling of paper, from a life cycle point of view, is environmentally equal or better than incineration with energy recovery only when the recycling technology is at a high environmental performance level. However, the modelling also showed that expanding the System to include substitution of fossil fuel energy by production of energy from the saved biomass associated with recycling will give a completely different result. In this case recycling is always more beneficial than incineration, thus increased recycling is desirable. Expanding the System to include forestry was shown to have a minor effect on the results. As assessments are often performed with a set choice of data and a set recycling rate, it is questionable how useful the results from this kind of LCA are for a policy maker. The high significance of the System Boundary choices stresses the importance of scientific discussion on how to best address System analysis of recycling, for paper and other recyclable materials.
Yi Yang - One of the best experts on this subject based on the ideXlab platform.
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Moving from completing System boundaries to more realistic modeling of the economy in life cycle assessment
2019Co-Authors: Yi Yang, Heijungs ReinoutAbstract:Purpose: Existing process-based life cycle assessment (LCA) models can be supplemented by input-output (IO) models to correct for the so-called truncation error resulting from an “incomplete” System Boundary. The resulting hybrid LCA is not necessarily but probably a closer approximation to an ideally complete process model with a global all-inclusive System Boundary. Here, we discuss whether such a complete process model is a goal worth pursuing and whether System Boundary is the main limitation of process-based LCA. Methods: We argue that the results of the ideally complete process model, with every single economic activity on earth embodied within, have little to limited implications and relevance for the decisions which LCA seeks to support and which involve changes aimed at reducing environmental impacts through altering product Systems or promoting alternatives. The main limitations of process-based LCA, as a supply chain based linear model, lie not in the “incomplete” System Boundary but in the narrow focus on supply chain and the unrealistic assumptions, such as omission of price effects and constraints. These assumptions reflect poorly how the economy works. Hybrid LCA, through adding IO models, which are also supply chain and linearity based, doubles down on both the narrow focus on supply chain and the unrealistic assumptions, and thus is a step forward but in the wrong direction. Results and discussion: Reflecting on advances in corn ethanol research, we show that pursuing a more complete System Boundary by, for instance, covering Chinese stuffed animal production does not make the LCA results more accurate or relevant for determining if corn ethanol in the US should be promoted. Not only is the theoretical argument for including Chinese stuffed animal industry tenuous, but there is no evidence it has been affected by US corn ethanol expansion. And by worrying about processes far away up the supply chain could distract us from focusing on the actual market mechanisms, such as indirect land use change, that are more likely to occur and are essential to predicting whether promoting corn ethanol would reduce total carbon emissions. Conclusions: We suggest future studies shifting focus from “completing” System Boundary within the conventional supply chain and linear framework towards more realistic modeling of our complicated human-environment System. Instead of trying to always include everything, we argue for a flexible and market-based System Boundary tailored to the decision in question, particularly considering the scale of potential changes it may cause and how it may affect the economy. A change at larger scales is likely to have a broader impact, thus justifying the definition of a broader System Boundary. But to cover a broad System Boundary for a small change will likely result in overestimates. More is not necessarily better
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moving from completing System boundaries to more realistic modeling of the economy in life cycle assessment
International Journal of Life Cycle Assessment, 2019Co-Authors: Yi Yang, Reinout HeijungsAbstract:Existing process-based life cycle assessment (LCA) models can be supplemented by input-output (IO) models to correct for the so-called truncation error resulting from an “incomplete” System Boundary. The resulting hybrid LCA is not necessarily but probably a closer approximation to an ideally complete process model with a global all-inclusive System Boundary. Here, we discuss whether such a complete process model is a goal worth pursuing and whether System Boundary is the main limitation of process-based LCA. We argue that the results of the ideally complete process model, with every single economic activity on earth embodied within, have little to limited implications and relevance for the decisions which LCA seeks to support and which involve changes aimed at reducing environmental impacts through altering product Systems or promoting alternatives. The main limitations of process-based LCA, as a supply chain based linear model, lie not in the “incomplete” System Boundary but in the narrow focus on supply chain and the unrealistic assumptions, such as omission of price effects and constraints. These assumptions reflect poorly how the economy works. Hybrid LCA, through adding IO models, which are also supply chain and linearity based, doubles down on both the narrow focus on supply chain and the unrealistic assumptions, and thus is a step forward but in the wrong direction. Reflecting on advances in corn ethanol research, we show that pursuing a more complete System Boundary by, for instance, covering Chinese stuffed animal production does not make the LCA results more accurate or relevant for determining if corn ethanol in the US should be promoted. Not only is the theoretical argument for including Chinese stuffed animal industry tenuous, but there is no evidence it has been affected by US corn ethanol expansion. And by worrying about processes far away up the supply chain could distract us from focusing on the actual market mechanisms, such as indirect land use change, that are more likely to occur and are essential to predicting whether promoting corn ethanol would reduce total carbon emissions. We suggest future studies shifting focus from “completing” System Boundary within the conventional supply chain and linear framework towards more realistic modeling of our complicated human-environment System. Instead of trying to always include everything, we argue for a flexible and market-based System Boundary tailored to the decision in question, particularly considering the scale of potential changes it may cause and how it may affect the economy. A change at larger scales is likely to have a broader impact, thus justifying the definition of a broader System Boundary. But to cover a broad System Boundary for a small change will likely result in overestimates. More is not necessarily better.
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hybrid life cycle assessment lca does not necessarily yield more accurate results than process based lca
Journal of Cleaner Production, 2017Co-Authors: Yi Yang, Reinout Heijungs, Miguel BrandaoAbstract:Hybrid life cycle assessment (LCA), through combining input-output (IO) models and process-based LCA for a complete System Boundary, is widely recognized as a more accurate approach than process-based LCA with an incomplete System Boundary. Without a complete process model for verification, however, the performance of hybrid LCA remains unclear. Here, using a counterexample we show that hybrid LCA does not necessarily provide more accurate results than process-based LCA, simply because the aggregation of heterogeneous processes in IO models may introduce more errors. In so doing, we prove that only when IO-based LCA and process-based LCA have the same level of detail would they yield the same results. Whether hybrid LCA provides more accurate estimates depends on whether the IO model introduced serves as an adequate proxy for the missing products as opposed to if they were estimated by a complete process model. The use of a highly-aggregated IO model runs the risk of overestimation, and could result in a larger relative error than the truncation error resulting from an incomplete process model. Our study seeks to provide a balanced view of hybrid LCA, and our findings offer important insights for future hybrid LCA studies to improve the accuracy and realm of applicability of the approach.
Lars Coenen - One of the best experts on this subject based on the ideXlab platform.
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why space matters in technological innovation Systems mapping global knowledge dynamics of membrane bioreactor technology
Research Policy, 2014Co-Authors: Christian Binz, Bernhard Truffer, Lars CoenenAbstract:Studies on technological innovation Systems (TISs) often set spatial boundaries at the national level and treat supranational levels as a geographically undifferentiated and freely accessible global technological opportunity set. This article criticizes this conceptualization and proposes instead to analyze relevant actors, networks and processes in TIS from a relational perspective on space. It develops an analytical framework which allows investigating innovation processes (or ‘functions’) of a TIS at and across different spatial scales. Based on social network analysis of a co-publication dataset from membrane bioreactor technology, we illustrate how the spatial characteristics of collaborations in knowledge creation vary greatly over relatively short periods of time. This finding suggests that TIS studies should be more reflexive on System Boundary setting both regarding the identification and analysis of core processes as well as in the formulation of policy advice.
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why space matters in technological innovation Systems mapping global knowledge dynamics of membrane bioreactor technology
Research Policy, 2014Co-Authors: Christian Binz, Bernhard Truffer, Lars CoenenAbstract:Studies on technological innovation Systems (TISs) often set spatial boundaries at the national level and treat supranational levels as a geographically undifferentiated and freely accessible global technological opportunity set. This article criticizes this conceptualization and proposes instead to analyze relevant actors, networks and processes in TIS from a relational perspective on space. It develops an analytical framework which allows investigating innovation processes (or 'functions') of a TIS at and across different spatial scales. Based on social network analysis of a co-publication dataset from membrane bioreactor technology, we illustrate how the spatial characteristics of collaborations in knowledge creation vary greatly over relatively short periods of time. This finding suggests that TIS studies should be more reflexive on System Boundary setting both regarding the identification and analysis of core processes as well as in the formulation of policy advice. (C) 2013 Elsevier B.V. All rights reserved. (Less)
