NDLI: Pre-calculated LCIs with uncertainties revisited

Content Provider	Springer Nature Link
Author	Suh, Sangwon Qin, Yuwei
Copyright Year	2017
Abstract	Heijungs et al. (Int J Life Cycle Assess 22(3):461, 2017) argued that (1) dependent sampling is required when analyzing uncertainties using Monte Carlo simulation in a comparative life cycle assessment (LCA) and that (2) using pre-calculated geometric standard deviations (GSDs) will lead to a “large overestimation” of the uncertainty of the results in a comparative LCA. While we agree with Heijungs and colleagues on the former from a theoretical standpoint, we find that the latter needs to be substantiated empirically. With this article, we tested the hypothesis that the use of pre-calculated life cycle inventories (LCIs) leads to an overestimation of uncertainty. In addition, we clarified a number of relevant issues and misconceptions in and around the independent sampling.We compared the GSDs of LCIs for 100 randomly selected Ecoinvent processes that were derived (1) using pre-calculated GSD values (partially independent sampling PIS) and (2) without using pre-calculated values (fully dependent sampling FDS). We tested the null hypothesis, E(GSD $^{ FDS }$/GSD $^{ PIS }$) < 1, using a t test.The difference in the GSDs from fully dependent sampling and partially independent sampling (using pre-calculated LCIs) was statistically significant, though the average ratio GSD $^{ FDS }$/GSD $^{ PIS }$ was very close to 1. Furthermore, the average ratio was larger than 1 with the confidence interval ranging from 1.0681 to 1.0696 at the 95% confidence level. Therefore, the null hypothesis was rejected.According to our empirical analyses, the use of pre-calculated LCIs and associated GSDs leads to a slight underestimation rather than an overestimation—not to mention “large overestimation”—of uncertainties in the results. GSDs in the results derived from pre-calculated LCIs and associated GSDs are very close to those derived from fully dependent sampling, and therefore, in practice, pre-calculated LCIs can be used as a reasonable proxy in understanding the uncertainties and variabilities of both non-comparative and comparative LCAs. Given the high uncertainty in the uncertainty analysis itself, the minor difference between GSDs from pre-calculated values and fully dependent sampling should not prevent LCA practitioners from using pre-calculated LCIs and corresponding GSDs for uncertainty analysis when no better option is reasonably practicable.
Starting Page	827
Ending Page	831
Page Count	5
File Format	PDF
ISSN	09483349
Journal	The International Journal of Life Cycle Assessment
Volume Number	22
Issue Number	5
e-ISSN	16147502
Language	English
Publisher	Springer Berlin Heidelberg
Publisher Date	2017-02-28
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Environment Environmental Economics Environmental Engineering/Biotechnology Environmental Chemistry
Content Type	Text
Resource Type	Article
Subject	Environmental Science

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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