Inventory compilation for renewable energy systems: the pitfalls of materiality thresholds and priority impact categories using hydropower case studies
Inventory compilation for renewable energy systems: the pitfalls of materiality thresholds and priority impact categories using hydropower case studies
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可再生能源系统清单编制：利用水电案例研究的重要性阈值和优先影响类别的陷阱
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发表时间：
2015
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通讯作者：
A. P. Williams
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作者：
J. Gallagher;D. Styles;A. McNabola;A. P. Williams
本文探讨了简化水电系统生命周期评估（LCA）过程的可能性，同时又不会显著影响环境负担的准确表示。通过对五个惠普案例的研究，我们解决了两个问题：(i) 1%的重要性阈值是否涵盖了从摇篮到运营过程中至少95%的关键环境负担？（ii）应用基于全球变暖潜势（GWP）指标的重要性阈值来捕捉其他环境影响的效果是什么？方法为五个现代小型和微型hp案例研究（50-650千瓦）开发了一个全面详细的库存数据库，代表了来自英国和爱尔兰的河流径流和供水基础设施设施。按照ISO 14040标准，对这些惠普项目的环境负担进行了量化。将归一化结果与天然气联合循环发电厂（NG-CCP）边际电网发电参考系统进行比较。结果和讨论一些指导方针建议采用1%的重要性阈值，导致一些HP安装的累计遗漏高达项目总负担的7.5%，违反了95%的包含目标。两种类型的HP项目的项目组件的数量不同，并且具有更多组件的项目更有可能超出目标。使用较低的0.2或0.5%的重要性阈值确保了95%的目标在所有HP项目中实现。将全球变暖潜能值作为评估重要性阈值的指标负担导致对其他环境负担的重大遗漏，例如非生物资源枯竭潜力（ARDP）。忽略了一些小的低碳组件（例如铜线），导致对资源基础（GWP）影响类别的贡献者低估了19%。结论：简化的方法可能无法涵盖水电系统或化石燃料发电厂的所有环境负担。对单一负担（如全球升温潜能值）的贡献设定1%的重要性阈值，可能导致该负担的重要贡献成分被忽略，而其他负担的贡献成分被更大程度地忽略。ARDP是可再生能源系统的一个特别重要的影响类别，似乎对物质阈值特别敏感。从业者在通过LCA评估所有类型的可再生能源系统的环境绩效时，注意重要性阈值是很重要的。必须包括一个重要性阈值，以划定切实可行的系统边界；然而，将阈值贡献降低到0.5%更有可能确保至少95%的环境负担得到考虑。
PurposeThis paper explores the potential to simplify the life cycle assessment (LCA) process for a hydropower (HP) system, without significantly compromising the accurate representation of environmental burdens. Taking five HP case studies, two questions were addressed: (i) Does a 1 % materiality threshold capture at least 95 % of the key environmental burdens from cradle-to-operation? (ii) What is the effect of applying a materiality threshold based on the global warming potential (GWP) indicator for capturing other environmental impacts?MethodsA comprehensively detailed inventory database was developed for five modern small- and micro-HP case studies (50–650 kW), representing run-of-river and water supply infrastructure installations from the UK and Ireland. Following ISO 14040 standards, the environmental burdens were quantified for these HP projects. Normalised results were compared against a natural gas combined cycle power plant (NG-CCP) reference system for marginal grid electricity generation.Results and discussionThe adoption of a 1 % materiality threshold as advised by some guidelines led to cumulative omissions of up to 7.5 % of the total project burdens for some HP installations, contravening the 95 % inclusion target. The number of project components differed between the two types of HP projects and target exceedances were more likely for projects with more components. Using a lower materiality threshold of 0.2 or 0.5 % ensured that the 95 % target was achieved for all HP projects. Considering GWP as an indicator burden for assessing materiality thresholds led to significant omissions for other environmental burdens, e.g. abiotic resource depletion potential (ARDP). Omitting a number of small components with low-carbon contributions (e.g. copper wiring) led to a 19 % underestimation for contributors to the resource-based (GWP) impact categories.ConclusionsA simplified methodology may not capture all environmental burdens for a hydropower system or fossil fuel-based power plant. Basing a 1 % materiality threshold on contribution to a single burden, such as GWP, can lead to omissions of significant contributory components for that burden, and larger omissions for other burdens. ARDP is a particularly important impact category for renewable energy systems and appears to be particularly sensitive to materiality thresholds. It is important that practitioners take care with materiality thresholds when evaluating the environmental performance of all types of renewable energy systems through LCA. Including a materiality threshold to draw practicable system boundaries is necessary; however, reducing the threshold contribution to 0.5 % would be more likely to ensure that at least 95 % of environmental burdens are accounted for.