| 1. |
- Beltran, Angelica Mendoza, et al.
(författare)
-
Quantified Uncertainties in Comparative Life Cycle Assessment : What Can Be Concluded?
- 2018
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:4, s. 2152-2161
-
Tidskriftsartikel (refereegranskat)abstract
- Interpretation of comparative Life Cycle Assessment (LCA) results can be challenging in the presence of uncertainty. To aid in interpreting such results under the goal of any comparative LCA, we aim to provide guidance to practitioners by gaining insights into uncertainty-statistics methods (USMs). We review five USMs-discernibility analysis, impact category relevance, overlap area of probability distributions, null hypothesis significance testing (NHST), and modified NHST- and provide a common notation, terminology, and calculation platform. We further cross-compare all USMs by applying them to a case study on electric cars. USMs belong to a confirmatory or an exploratory statistics' branch, each serving different purposes to practitioners. Results highlight that common uncertainties and the magnitude of differences per impact are key in offering reliable insights. Common uncertainties are particularly important as disregarding them can lead to incorrect recommendations. On the basis of these considerations, we recommend the modified NHST as a confirmatory USM. We also recommend discernibility analysis as an exploratory USM along with recommendations for its improvement, as it disregards the magnitude of the differences. While further research is necessary to support our conclusions, the results and supporting material provided can help LCA practitioners in delivering a more robust basis for decision-making.
|
|
| 2. |
- Brandao, Miguel, et al.
(författare)
-
On quantifying sources of uncertainty in the carbon footprint of biofuels : crop/feedstock, LCA modelling approach, land-use change, and GHG metrics
- 2022
-
Ingår i: Biofuel Research Journal. - : Greenwave Publishing of Canada. - 2292-8782. ; 9:2, s. 1608-1616
-
Tidskriftsartikel (refereegranskat)abstract
- Biofuel systems may represent a promising strategy to combat climate change by replacing fossil fuels in electricity generation and transportation. First-generation biofuels from sugar and starch crops for ethanol (a gasoline substitute) and from oilseed crops for biodiesel (a petroleum diesel substitute) have come under increasing levels of scrutiny due to the uncertainty associated with the estimation of climate change impacts of biofuels, such as due to indirect effects on land use. This analysis estimates the magnitude of some uncertainty sources: i) crop/feedstock, ii) life cycle assessment (LCA) modelling approach, iii) land-use change (LUC), and iv) greenhouse gas (GHG) metrics. The metrics used for characterising the different GHGs (global warming potential-GWP and global temperature change potential-GTP at different time horizons) appeared not to play a significant role in explaining the variance in the carbon footprint of biofuels, as opposed to the crop/feedstock used, the inclusion/exclusion of LUC considerations, and the LCA modelling approach (p<0.001). The estimated climate footprint of biofuels is dependent on the latter three parameters and, thus, is context-specific. It is recommended that these parameters be dealt with in a manner consistent with the goal and scope of the study. In particular, it is essential to interpret the results of the carbon footprint of biofuel systems in light of the choices made in each of these sources of uncertainty, and sensitivity analysis is recommended to overcome their influence on the result.
|
|
| 3. |
- Finnveden, Göran, et al.
(författare)
-
Recent developments in Life Cycle Assessment
- 2009
-
Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 91:1, s. 1-21
-
Tidskriftsartikel (refereegranskat)abstract
- Life Cycle Assessment is a tool to assess the environmental impacts and resources used throughout a product's life cycle, i.e., from raw material acquisition, via production and use phases, to waste management. The methodological development in LCA has been strong, and LCA is broadly applied in practice. The aim of this paper is to provide a review of recent developments of LCA methods. The focus is on some areas where there has been an intense methodological development during the last years. We also highlight some of the emerging issues. In relation to the Goal and Scope definition we especially discuss the distinction between attributional and consequential LCA. For the Inventory Analysis, this distinction is relevant when discussing system boundaries, data collection, and allocation. Also highlighted are developments concerning databases and Input-Output and hybrid LCA. In the sections on Life Cycle Impact Assessment we discuss the characteristics of the modelling as well as some recent developments for specific impact categories and weighting. In relation to the Interpretation the focus is on uncertainty analysis. Finally, we discuss recent developments in relation to some of the strengths and weaknesses of LCA.
|
|
| 4. |
- Finnveden, Göran, et al.
(författare)
-
Six areas of methodological debate on attributional life cycle assessment
- 2022
-
Ingår i: E3S Web of Conferences. - : EDP Sciences. - 2267-1242 .- 2555-0403. ; 349, s. 03007-03007
-
Tidskriftsartikel (refereegranskat)abstract
- There is a general agreement in the LCA community that there are two types of LCAs: attributional and consequential. There have been numerous discussions about the pros and cons of the two approaches and on differences in methodology, in particular about methods that can be used in consequential LCA.There are, however, methodological aspects of attributional LCA and how it can be used that need further attention. This article discusses six areas of debate and potential misunderstandings concerning attributional LCA. These are:1) LCA results of all the products in the world should add up to the total environmental impact of the world, sometimes referred to as the 100 % rule.2) Attributional LCA is less relevant than consequential LCA.3) System expansion, and/or substitution, cannot be used in attributional LCA.4) Attributional LCA leads to more truncation errors than consequential LCA does.5) There is a clear connection between the goal and questions of an LCA and the choice of attributional or consequential LCA.6) There is a clear boundary between attributional and consequential LCA. In the article, these statements are discussed, and it is argued that they are either misunderstandings or sometimes incorrect.
|
|
| 5. |
- Heijungs, Reinout, et al.
(författare)
-
Everything is relative and nothing is certain. Toward a theory and practice of comparative probabilistic LCA
- 2019
-
Ingår i: The International Journal of Life Cycle Assessment. - : Springer Science and Business Media LLC. - 0948-3349 .- 1614-7502. ; 24:9, s. 1573-1579
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction It is widely recognized that LCA is in most cases relative and contains uncertainties due to choices and data. This paper analyses the combination of the two comparative uncertainties. Basic concepts We carefully define the idea of relativity and uncertainty within LCA. We finish off by giving an example of case where inappropriate handling of comparative uncertainties will lead to a misleading result for a decision-maker. Correlations We develop a generic framework for probabilistic comparative LCA and analyse at which places correlations may be present. We also discuss the most convenient approaches for handling such correlated uncertainties. Conclusion We put the elements discussed in a structure that provides a research agenda for dealing with comparative uncertainties in LCA.
|
|
| 6. |
|
|
| 7. |
- Heijungs, Reinout, et al.
(författare)
-
Response : Commentary
- 2021
-
Ingår i: Frontiers in Sustainability. - : Frontiers Media SA. - 2673-4524. ; 2
-
Tidskriftsartikel (refereegranskat)
|
|
| 8. |
|
|
| 9. |
- Nyberg, Oskar, et al.
(författare)
-
Ecotoxicological HC20-values and their statistical distribution : A nonlinear weighted regression applied to thousands of chemicals
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Ecotoxicological effect data which form the basis of evaluations of ecological impacts from chemical emissions are incomplete, and completely absent for some chemicals, which result in risks being overlooked. Where data are available, they tend to be heterogeneous and accompanied with large uncertainties. In the present research we curate ecotoxicological data from openly available sources and present a methodology for quantifying the variability in toxicity for chemicals and evaluate its implications for environmental assessment frameworks, such as life cycle assessments.The data collection resulted in a database detailing 118,131 curated records that span 1,736 species and 3,692 chemicals suitable for calculating the concentration response slope factors corresponding to the slope on the SSD curve at the 20% response level of organisms exposed to a chemical (CRFHC20). From these data we are able to calculate values and 95% percentile distributions of the CRFHC20 for 2,350 and 1,117 chemicals respectively. Pesticides is the most data rich category of chemicals, yet has the largest variability attached to the CRFHC20.We show that the variance among toxicity estimates for the same species and chemical can be used in weighted nonlinear model fitting to generate an uncertainty range attached to a CRFHC20 value, allowing for uncertainties related to ecotoxicological impact characterization in environmental frameworks to be estimated. Data scarcity is an omnipresent issue when it comes to characterizing toxicity of chemicals, where only 63.7 % of all chemicals with effect data records have enough data to calculate a CRFHC20 value, and 30.3 % have enough data to fit a weighted nonlinear least squares model. Our recommendation is to incorporate toxicological variance in estimations of ecotoxicity impacts and life cycle impact assessment categories, to reduce ambiguity and allow for verification when comparing ecotoxicological impacts.
|
|
| 10. |
|
|
| 11. |
- Schaubroeck, Thomas, et al.
(författare)
-
Attributional & Consequential Life Cycle Assessment : Definitions, Conceptual Characteristics and Modelling Restrictions
- 2021
-
Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 13:13, s. 7386-
-
Tidskriftsartikel (refereegranskat)abstract
- To assess the potential environmental impact of human/industrial systems, life cycle assessment (LCA) is a very common method. There are two prominent types of LCA, namely attributional (ALCA) and consequential (CLCA). A lot of literature covers these approaches, but a general consensus on what they represent and an overview of all their differences seems lacking, nor has every prominent feature been fully explored. The two main objectives of this article are: (1) to argue for and select definitions for each concept and (2) specify all conceptual characteristics (including translation into modelling restrictions), re-evaluating and going beyond findings in the state of the art. For the first objective, mainly because the validity of interpretation of a term is also a matter of consensus, we argue the selection of definitions present in the 2011 UNEP-SETAC report. ALCA attributes a share of the potential environmental impact of the world to a product life cycle, while CLCA assesses the environmental consequences of a decision (e.g., increase of product demand). Regarding the second objective, the product system in ALCA constitutes all processes that are linked by physical, energy flows or services. Because of the requirement of additivity for ALCA, a double-counting check needs to be executed, modelling is restricted (e.g., guaranteed through linearity) and partitioning of multifunctional processes is systematically needed (for evaluation per single product). The latter matters also hold in a similar manner for the impact assessment, which is commonly overlooked. CLCA, is completely consequential and there is no limitation regarding what a modelling framework should entail, with the coverage of co-products through substitution being just one approach and not the only one (e.g., additional consumption is possible). Both ALCA and CLCA can be considered over any time span (past, present & future) and either using a reference environment or different scenarios. Furthermore, both ALCA and CLCA could be specific for average or marginal (small) products or decisions, and further datasets. These findings also hold for life cycle sustainability assessment.
|
|
| 12. |
- van Oers, Lauran, et al.
(författare)
-
Top-down characterization of resource use in LCA : from problem definition of resource use to operational characterization factors for dissipation of elements to the environment
- 2020
-
Ingår i: The International Journal of Life Cycle Assessment. - Cham, Switzerland : Springer Nature. - 0948-3349 .- 1614-7502. ; 25:11, s. 2255-2273
-
Tidskriftsartikel (refereegranskat)abstract
- PurposeThe methods for assessing the impact of using abiotic resources in life cycle assessment (LCA) have always been heavily debated. One of the main reasons for this is the lack of a common understanding of the problem related to resource use. This article reports the results of an effort to reach such common understanding between different stakeholder groups and the LCA community. For this, a top-down approach was applied.MethodsTo guide the process, a four-level top-down framework was used to (1) demarcate the problem that needs to be assessed, (2) translate this into a modeling concept, (3) derive mathematical equations and fill these with data necessary to calculate the characterization factors, and (4) align the system boundaries and assumptions that are made in the life cycle impact assessment (LCIA) model and the life cycle inventory (LCI) model.ResultsWe started from the following definition of the problem of using resources: the decrease of accessibility on a global level of primary and/or secondary elements over the very long term or short term due to the net result of compromising actions. The system model distinguishes accessible and inaccessible stocks in both the environment and the technosphere. Human actions can compromise the accessible stock through environmental dissipation, technosphere hibernation, and occupation in use or through exploration. As a basis for impact assessment, we propose two parameters: the global change in accessible stock as a net result of the compromising actions and the global amount of the accessible stock. We propose three impact categories for the use of elements: environmental dissipation, technosphere hibernation, and occupation in use, with associated characterization equations for two different time horizons. Finally, preliminary characterization factors are derived and applied in a simple illustrative case study for environmental dissipation.ConclusionsDue to data constraints, at this moment, only characterization factors for “dissipation to the environment” over a very-long-term time horizon could be elaborated. The case study shows that the calculation of impact scores might be hampered by insufficient LCI data. Most presently available LCI databases are far from complete in registering the flows necessary to assess the impacts on the accessibility of elements. While applying the framework, various choices are made that could plausibly be made differently. We invite our peers to also use this top-down framework when challenging our choices and elaborate that into a consistent set of choices and assumptions when developing LCIA methods.
|
|
