Hybrid life-cycle assessment for robust, best-practice carbon accounting

Abstract

19In order to meet internationally agreed targets for avoiding dangerous 20 anthropogenic climate change, an absolute priority for global society is to rapidly 21 stabilise and then reduce carbon dioxide emissions into the atmosphere. Any entity, 22 be it individual, company, or nation state, is more able to reduce its carbon dioxide 23 (and other greenhouse gas) emissions if these can be quantified and attributed and 24 the effects of interventions estimated. The current state of product and supply chain 25 carbon accounting methods does not consistently meet the standards required to 26 tackle this global challenge. This study therefore aims to identify key methodological 27 practices affecting the accuracy of carbon accounting models and in particular to 28 assess the effects of the system boundaries they employ. Models currently available 29 for estimating carbon emissions are either input-output based (using macro-30 economic analysis), process-based (using specific carbon emissions attributes 31 through the life-cycle of a product, service or event), or a hybrid of the two. Here, a 32 detailed comparison has been made between various input-output and process-33 based models and the results compared with those from a hybrid model that was 34 taken to represent 'best practice' in carbon accounting. Key factors affecting 35 accuracy were found to lie in: the detail of methodological decisions for input-output 36 models, the economic region or regions upon which the model is based, and the 37 quality, disaggregation and, especially for price-volatile products, the temporal 38 alignment of the data. The relative significance of these factors is explored. For 39 copper wire, a system boundary gap analysis was conducted on an industry-leading 40 process-based model (GREET.net) compared with a complete system as described by 41 the best performing input-output model. GREET.net was found to suffer a 60% 42 truncation error. The copper wire example demonstrates the practicality of 43 substituting process-based analysis into input-output based supply chain emissions 44 assessments. 45 46 Key words 47 Carbon accounting; embodied carbon; input-output models; life cycle analysis; 48 process-based analysis 49 50 M

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Past, present, and future of carbon accounting: Insights from scholarly research

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The greenhouse gas emissions of nuclear energy – Life cycle assessment of a European pressurised reactor

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