Ready-to-use and advanced methodologies to prioritise the regionalisation effort in LCA
Bibliographic record
Abstract
The spatial dimension is an important aspect in life cycle assessment (LCA). Indeed life cycle processes, and therefore also elementary flows, are most likely to be geographically scattered due to global supply chains. The environmental impacts related to an elementary flow can be different across the globe depending on the spatial variability of ecosystem sensitivity. Integrating spatial dimension seems to be a promising way to increase LCA results’ reliability by reducing spatial uncertainties. LCA regionalisation refers to the integration of the spatial variability that really exists to improve result representativeness and reduce spatial uncertainties. As regionalisation requires additional effort for LCA practitioners, it is necessary to ensure the interest of such an effort and to prioritise it. This work proposes two methodologies to prioritise the regionalisation effort in LCA depending on the decision context and the type of study. They allow the selection of impacts, processes and regionalisation aspects that LCA practitioners need to focus on. The first one is a ready-to-use methodology and the second one involves more advanced tools based on spatial uncertainty analysis. The proposed methodologies are stepwise. The ready-to-use methodology involves tools that are already used by LCA practitioners and is based on impact contribution analysis. Regarding the advanced methodology, most relevant impact categories and processes to be further investigated for regionalisation are selected according to their impact contribution and their uncertainty level by using Monte Carlo simulation and regression analysis. The regionalisation effort is estimated depending on the confidence level required for the case study. The relevance and limits of each methodologies are investigated. Results underline the importance to take into account both impact and uncertainty contributions to select processes that need to be regionalised. The proposed methodologies highlight the need to focus on the goal and scope at the early stages of a study in order to clearly identify the intended audience and its requirements regarding study quality. A dialogue with the decision maker during the study would be beneficial. Those approaches can be relevant for other types of uncertainty but should be adapted.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.014 | 0.021 |
| Meta-epidemiology (narrow) | 0.003 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.003 |
| Bibliometrics | 0.008 | 0.004 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".