Christoph Koffler

Normalisation and weighting in life cycle assessment: quo vadis?

PurposeBuilding on the rhetoric question “quo vadis?” (literally “Where are you going?”), this article critically investigates the state of the art of normalisation and weighting approaches within life cycle assessment. It aims at identifying purposes, current practises, pros and cons, as well as research gaps in normalisation and weighting. Based on this information, the article wants to provide guidance to developers and practitioners. The underlying work was conducted under the umbrella of the UNEP-SETAC Life Cycle Initiative, Task Force on Cross-Cutting issues in life cycle impact assessment (LCIA).MethodsThe empirical work consisted in (i) an online survey to investigate the perception of the LCA community regarding the scientific quality and current practice concerning normalisation and weighting; (ii) a classification followed by systematic expert-based assessment of existing methods for normalisation and weighting according to a set of five criteria: scientific robustness, documentation, coverage, uncertainty and complexity.Results and discussionThe survey results showed that normalised results and weighting scores are perceived as relevant for decision-making, but further development is needed to improve uncertainty and robustness. The classification and systematic assessment of methods allowed for the identification of specific advantages and limitations.ConclusionsBased on the results, recommendations are provided to practitioners that desire to apply normalisation and weighting as well as to developers of the underlying methods.

Volkswagen slimLCI: a procedure for streamlined inventory modelling within life cycle assessment of vehicles

One of the key prerequisites of environmentally-friendly product design is a quantitative assessment of the environmental profile of product design options. Life Cycle Assessment (LCA) is a tool for evaluating the environmental performance of goods and services over the whole life cycle. Yet, the effort involved remains one major obstacle for its wide-spread use. It is well-known that collecting and processing the relevant data is the most time-consuming part while conducting an LCA study of complex systems. It is possible to reduce the workload significantly by automating these process steps, which also offers advantages in terms of LCA quality.

Life cycle assessment capacity roadmap (section 1): decision-making support using LCA

When life cycle assessment (LCA) results do not show a clear and certain environmental preference of one choice over one or several alternatives, current methods are limited in their ability to inform decision-makers. To address this and related cross-cutting issues, a group of LCA practitioners has been working on a roadmap for capacity development in LCA. The roadmap is identifying common needs for development in LCA, which can then be addressed by the broader LCA community. The roadmap document on decision-making support, having undergone a public comment period, outlines the current state as well as needs and milestones to ensure progress continues apace. The roadmap document, available for download, covers five main areas of development: (1) performance measures of confidence, which identify the acceptable uncertainty for study results, while minimizing expenditures; (2) selection of impact categories, an area with multiple existing methods. The roadmap suggests codifying these methods and identifying their suitability to various applications; (3) normalization; while several methods of normalization are in use, the method with the greatest acceptance in the LCA community (i.e., relying on total or per capita regional emissions/extractions) has a number of methodological drawbacks; (4) weighting, which is a form of multi-criteria decision analysis (MCDA). The broader MCDA field can enrich LCA by providing studied methods of assessing trade-offs; and (5) visualization of results. Many other LCA capacity needs would benefit from documentation. These include but are not limited to the following: addressing ill-characterized uncertainty, life cycle inventory data needs, data format needs, and tool capabilities. Other roadmapping groups are forming and are looking for practitioners to support the effort.

Automobiler Leichtbau unter Einbezug des gesamten Lebenszyklus

Moderne Leichtbauweisen sind eine der Schlusseltechnologien fur eine effiziente und zukunftsfahige Mobilitat. Neben der Erfullung aller technischen Anforderungen hat sich die Volkswagen AG zum Ziel gesetzt, auch die Umweltvertraglichkeit ihrer Produkte kontinuierlich zu verbessern. Dies erfolgt fruhzeitig im Entwicklungsprozess stets unter Einbezug des gesamten Lebenswegs. Die Okobilanz nach ISO 14040/44 ermoglicht es, die Umweltvertraglichkeit quantitativ zu bewerten und die Entscheidungsfindung zu unterstutzen.

LCA capability roadmap—product system model description and revision

PurposeLife cycle assessment (LCA) practitioners face many challenges in their efforts to describe, share, review, and revise their product system models, and to reproduce the models and results of others. Current life cycle inventory modeling techniques have weaknesses in the areas of describing model structure, documenting the use of proxy or non-ideal data, specifying allocation, and including modeler’s observations and assumptions—all affecting how the study is interpreted and limiting the reuse of models. Moreover, LCA software systems manage modeling information in different and sometimes non-compatible ways. Practitioners must also deal with licensing, privacy/confidentiality of data, and other issues around data access which impact how a model can be shared.MethodsThis letter was prepared by a working group of the North American Life Cycle Assessment Advisory Group to support the UNEP-SETAC Life Cycle Initiative’s Flagship Activity on Data, Methods, and Product Sustainability Information. The aim of the working group is to define a roadmap of the technical advances needed to achieve easier LCA model sharing and improve replicability of LCA results among different users in a way that is independent of the LCA software used to compute the results and does not infringe on any licensing restrictions or confidentiality requirements. This is intended to be a consensus document providing the state of the art in this area, with milestones for research and implementation needed to resolve current issues.Results and ConclusionsThe roadmap identifies fifteen milestones in three areas: “describing model contents,” “describing model structure,” and “collaborative use of models.” The milestones should support researchers and software developers in advancing practitioners’ abilities to share and review product system models.

An integrated life cycle approach to lightweight automotive design

Modern lightweight design techniques are one of the key technologies in the development of efficient and sustainable mobility solutions. Volkswagen AG aims to ensure that as well as meeting all the necessary technical requirements, its products also deliver continuously improved environmental performance. Right from the start of the development process, these efforts are always focused on the full life cycle of the product. Life Cycle Assessments (LCA) based on ISO 14040/44 allow life cycle environmental impacts to be quantified, so that they can be taken into account in business decisions.

Are we still keeping it “real”? Proposing a revised paradigm for recycling credits in attributional life cycle assessment

PurposeEnd-of-life (EoL) recycling poses a challenge to many practitioners today due to the availability of different calculation approaches and the lack of scientific consensus, which is fueled by academic research and vested industry interests alike. One of the main challenges in EoL modeling is the credible calculation of the appropriate recycling credit in open-loop and closed-loop situations.MethodsWe believe that part of the challenge is caused by a lack of understanding of the underlying recycling paradigm, which refers to the meaning that is assigned to the recycling credit. Referred to as “system expansion through substitution” and “future displacement of primary production,” the two predominant paradigms are delineated from each other followed by a discussion of their remaining challenges.Results and discussionBased on these considerations, we propose a revised paradigm based on embodied burdens that is able to alleviate many of the most pressing issues associated with material recycling in attributional life cycle assessment.ConclusionsWith this discussion paper, we look forward to a productive and lively debate on the matter.

Beyond pedigree—optimizing and measuring representativeness in large-scale LCAs

PurposeData sampling strategies in large-scale life-cycle assessments (LCAs) are often developed informally based on a combination of sector expertise, common sense, resource restrictions, and politics. The assessment of the representativeness of the acquired sample is then assessed ex post in a qualitative fashion or using a semi-quantitative approach based on pedigree matrices. The purpose of this paper is twofold: provide a structured framework for both designing a representative sample for these types of studies as well as for assessing the representativeness of the sample one was able to obtain.MethodsFor sample design, we propose the use of proportionate stratified sampling after defining the strata through the identification of those population characteristics that are able to introduce a relevant bias to average specific environmental burdens of the product system under study. For assessment of the final representativeness of the acquired sample, we propose a metric based on the weighted average deviation between population and sample based on the identified strata for technological and geographical representativeness and another metric for temporal representativeness that is based on a weighting scale applied to the years that data was collected from.Results and discussionThe proposed approach is pragmatic and practical and helps to improve representativeness compared to simple random sampling. The general principles can inform the discussions about how many and which sites to sample even if detailed data on the composition of the population is missing. Its key strength is that it is not a one-size-fits-all methodology, but that it can and needs to be adapted to the product system under study, which in return requires the transparent documentation of all rationales and value choices along the way.ConclusionsThe proposed approach provides practitioners with a flexible framework to plan data collection in a way that increases representativeness compared to simple random sampling. The representativeness can be quantified and discussed using a defined scale that is based on quantitative measures rather than based on qualitative descriptions or pedigrees. If the underlying rationales and value choices are transparently documented and justified, the framework can help to improve how representativeness of primary data is addressed in large-scale LCAs.

Correction to: On the calculation of fuel savings through lightweight design in automotive life cycle assessments

In the 2010 volume 15 page 128–135 article “On the calculation of fuel savings through lightweight design in automotive life cycle assessments” (Koffler and Rohde-Brandenburger 2010) in the International Journal of Life Cycle Assessment.