A Methodology for Robust Comparative Life Cycle Assessments Incorporating Uncertainty

Gregory, Jeremy; Noshadravan, Arash; Olivetti, Elsa; Kirchain, Randolph

doi:10.1021/acs.est.5b04969

Cited by 66 publications

(50 citation statements)

References 24 publications

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“…As shown here, the overlap area uses quantitative uncertainty information, which can derive from inventory, characterization, and/or methodological choices (Mendoza Beltran et al 2016). We can identify relevant aspects of a comparison with the overlap area between probability distributions or other approaches that evaluate mutual differences (Heijungs and Kleijn 2001;Prado-Lopez et al 2014;Henriksson et al 2015;Gregory et al 2016;Wei et al 2016). These results do not suffer from the systematic biases of external normalization, as the outputs vary for each LCA application (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…For instance, discernibility analysis (Heijungs and Kleijn 2001) counts the times in which one alternative is greater than another in each Monte Carlo run. Following the same basis, but illustrating a more extensive approach with sensitivity analysis is the approach shown in Gregory et al (2016). The relevance parameter as introduced in PradoLopez et al (2014) evaluates the ratio of the differences in means to the standard deviations.…”

Section: Overlap Area Approachmentioning

confidence: 99%

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Interpretation of comparative LCAs: external normalization and a method of mutual differences

Prado

Wender

Seager

2017

Int J Life Cycle Assess

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Purpose Identification of environmentally preferable alternatives in a comparative life cycle assessment (LCA) can be challenging in the presence of multiple incommensurate indicators. To make the problem more manageable, some LCA practitioners apply external normalization to find those indicators that contribute the most to their respective environmental impact categories. However, in some cases, these results can be entirely driven by the normalization reference, rather than the comparative performance of the alternatives. This study evaluates the influence of normalization methods on interpretation of comparative LCA to facilitate the use of LCA in decision-driven applications and inform LCA practitioners of latent systematic biases. An alternative method based on significance of mutual differences is proposed instead. Methods This paper performs a systematic evaluation of external normalization and describes an alternative called the overlap area approach for the purpose of identifying relevant issues in a comparative LCA. The overlap area approach utilizes the probability distributions of characterized results to assess significant differences. This study evaluates the effects in three LCIA methods, through application of four comparative studies. For each application, we call attention to the category indicators highlighted by each interpretation approach. Results and discussion External normalization in the three LCIA methods suffers from a systematic bias that emphasizes the same impact categories regardless of the application. Consequently, comparative LCA studies that employ external normalization to guide a selection may result in recommendations dominated entirely by the normalization reference and insensitive to data uncertainty. Conversely, evaluation of mutual differences via the overlap area calls attention to the impact categories with the most significant differences between alternatives. The overlap area approach does not show a systematic bias across LCA applications because it does not depend on external references and it is sensitive to changes in uncertainty. Thus, decisions based on the overlap area approach will draw attention to tradeoffs between alternatives, highlight the role of stakeholder weights, and generate assessments that are responsive to uncertainty. Conclusions The solution to the issues of external normalization in comparative LCAs proposed in this study call for an entirely different algorithm capable of evaluating mutual differences and integrating uncertainty in the results.

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Section: Discussionmentioning

confidence: 99%

Section: Overlap Area Approachmentioning

confidence: 99%

Interpretation of comparative LCAs: external normalization and a method of mutual differences

Prado

Wender

Seager

2017

Int J Life Cycle Assess

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“…There concluded that there is a need both for more accurate simulation models and for procedural methods that integrate the energy results with other decisions. Gregory et al [45] used a decision-tree algorithm to compare alternative solutions in a life cycle perspective. This approach identified the most influential parameters in the scenarios, including parameters related to system boundaries.…”

Section: Methodsmentioning

confidence: 99%

“…The approach allows a simplification of multicriteria problems, reducing the computational time to identify the best options. As mentioned above, Gregory et al [45] proposed a methodology for making robust decisions under uncertainty, based on decision-tree algorithms and probability distributions. This method can also be used to address multicriteria decision problems.…”

Section: Methodsmentioning

confidence: 99%

From Zero Emission Buildings (ZEB) to Zero Emission Neighbourhoods (ZEN): A Mapping Review of Algorithm-Based LCA

2018

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Abstract:The building industry is responsible for approximately 40% of energy consumption and 36% of greenhouse gas emissions in the European Union (EU). The most efficient way of reducing a building's environmental impact is addressing it in the design stage. Here, design freedom is the greatest, but uncertainty is high and there is a nearly limitless number of design options. Based on experiences with zero emission buildings (ZEB) and zero emission neighbourhoods (ZEN), a mapping review has been conducted to analyse how parametric life cycle assessment (LCA) and algorithms have been used to address neighbourhoods, buildings, and construction materials. Results have identified a general gap of knowledge regarding the use of parametric LCA models for decision-support purposes, demonstrated by the substantial focus on analytical methods compared to procedural methods. Implications for the evolution from ZEB to ZEN are twofold: (i) an integrated approach with multiple tools and methods is required, and (ii) further development of algorithms in the tool are needed to address complexity, sensitivity, and uncertainty. This study is expected to foster the development of algorithmic approaches to improve the ZEB tool as a decision-support tool. Further research should address the key questions of when and how.

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“…This is particularly important as many economies strive towards circularity, where LCA systems will encounter more often multifunctional processes (Mendoza Beltran et al 2015). Despite some other studies treating uncertainty sources such as methodological choices, modeling assumptions, and inventory data u n c e r t a i n t y, b y m e a n s o f d i ff e r e n t a p p r o a c h e s (Andrianandraina et al 2015;Gregory et al 2016), we are not aware of any study so far treating uncertainty due to the choice of allocation method for all multi-functional background processes.…”

Section: Comparative Lcas With Uncertainty Analysismentioning

confidence: 99%

Accounting for inventory data and methodological choice uncertainty in a comparative life cycle assessment: the case of integrated multi-trophic aquaculture in an offshore Mediterranean enterprise

Beltrán

Chiantore

Pecorino

et al. 2017

Int J Life Cycle Assess

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Purpose Integrated multi-trophic aquaculture (IMTA), growing different species in the same space, is a technology that may help manage the environmental impacts of coastal aquaculture. Nutrient discharges to seawater from monoculture aquaculture are conceptually minimized in IMTA, while expanding the farm economic base. In this study, we investigate the environmental trade-offs for a small-to-medium enterprise (SME) considering a shift from monoculture towards IMTA production of marine fish. Methods A comparative life cycle assessment (LCA), including uncertainty analysis, was implemented for an aquaculture SME in Italy. Quantification and simultaneous propagation of uncertainty of inventory data and uncertainty due to the choice of allocation method were combined with dependent sampling to account for relative uncertainties and statistical testing and interpretation to understand the uncertainty analysis results. Monte Carlo simulations were used as a propagation method. The environmental impacts per kilo of fish produced in monoculture and in IMTA were compared. Twelve impact categories were considered. The comparison is first made excluding uncertainty (deterministic LCA) and then accounting for uncertainties. Results and discussion Deterministic LCA results evidence marginal differences between the impacts of IMTA and monoculture fish production. IMTA performs better on all impacts studied. However, statistical testing and interpretation of the uncertainty analysis results showed that only mean impacts for climate change are significantly different for both productive systems, favoring IMTA. For the case study, technical variables such as scales of production of the species from different trophic levels, their integration (space and time), and the choice of species determine the trade-offs. Also, LCA methodological choices such as that for an allocation method and the treatment of relative uncertainties were determinant in the comparison of environmental trade-offs. Conclusions The case study showed that environmental trade-offs between monoculture and IMTA fish production depend on technical variables and methodological choices. The combination of statistical methods to quantify, propagate, and interpret uncertainty was successfully tested. This approach supports more robust environmental trade-off assessments between alternatives in LCAs with uncertainty analysis by adding information on the significance of results. It was difficult to establish whether IMTA does bring benefits given

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A Methodology for Robust Comparative Life Cycle Assessments Incorporating Uncertainty

Cited by 66 publications

References 24 publications

Interpretation of comparative LCAs: external normalization and a method of mutual differences

Interpretation of comparative LCAs: external normalization and a method of mutual differences

From Zero Emission Buildings (ZEB) to Zero Emission Neighbourhoods (ZEN): A Mapping Review of Algorithm-Based LCA

Accounting for inventory data and methodological choice uncertainty in a comparative life cycle assessment: the case of integrated multi-trophic aquaculture in an offshore Mediterranean enterprise

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