Identification of ‘Carbon Hot-Spots’ and Quantification of GHG Intensities in the Biodiesel Supply Chain Using Hybrid LCA and Structural Path Analysis

Abstract

16It is expected that biodiesel production in the EU will remain the dominant contributor as part 17 of a 10% minimum binding target for biofuel in transportation fuel by 2020 within the 20% 18 renewable energy target in the overall EU energy mix. Life cycle assessments (LCA) of 19 biodiesel to evaluate its environmental impacts have, however, remained questionable, 20 mainly because of the adoption of a traditional process analysis approach resulting in system 21 boundary truncation and because of issues regarding the impacts of land use change and N 2 O 22 emissions from fertiliser application. In this study, a hybrid LCA methodology is used to 23 evaluate the life cycle CO 2 equivalent emissions of rape methyl ester (RME) biodiesel. The 24 methodology uses input-output analysis to estimate upstream indirect emissions in order to 25 complement traditional process LCA in a hybrid framework. It was estimated that traditional 26 LCA accounted for 2.7 kg CO 2 -eq per kg of RME or 36.6% of total life cycle emissions of 27 the RME supply chin. Further to the inclusion of upstream indirect impacts in the LCA 28 system (which accounted for 23% of the total life cycle emissions), emissions due to direct 29 land use change (6%) and indirect land use change (16.5%) and N 2 O emissions from fertiliser 30 shown, for instance, that inputs from the 'Other Chemical Products' sector (identified as 34 phosphoric acid, H 3 PO 4 ) into the biodiesel production process represented the highest carbon 35 emission path (or hot-spot) with 5.35% of total upstream indirect emissions of the RME 36 biodiesel supply chain. 37 38

Integrated hybrid life cycle assessment and supply chain environmental profile evaluations of lead-based (lead zirconate titanate) versus lead-free (potassium sodium niobate) piezoelectric ceramics

“…Integration of the two methods via a hybrid method augments the specificity of process LCA with the inclusivity of EIO 31,35,[41][42][43] ; hence hybrid LCA models can be implemented in practice to broaden the system boundary whilst complying with ISO standards. 41,44 In the hybrid LCA system, process LCA is interlinked with the complete supply chain system boundary provided by EIO model, which captures the entire economic supply chain along with its sectorial changes and production and consumption patterns.…”

“…28,30 As such, Life Cycle Assessment (LCA) can been used as a powerful tool to systematically track the broad spectrum of environmental impacts throughout the entire value chain of an activity, product or process and assess them from a systems perspective, identifying approaches for improvement without burden shifting. 28,30,31,35,53 LCA entails the gathering and evaluation of the inputs, outputs, and potential environmental impacts of a product system throughout its lifespan and involves four key steps 11 assessment, where emissions and resources are grouped into their respective impact categories and converted into common impact units for comparative analysis; (iv) the interpretation of the inventory and impact assessment of results in order to actualise the objectives of the study.To analyse the contributions of individual process exchange entries into the inventory based on a number of sustainability metrics, the LCA in this work is carried out, from cradle-tograve, across multiple sustainability metrics, based on CML method, 57 namely GHG emissions, land use, pollution (acidification and eutrophication potentials) and ecotoxicity (marine aquatic, marine sediment, fresh water sediment, fresh water aquatic, terrestrial etc. ), human toxicity, malodours air and ionisation radiation.…”

“…The current work adopts an integrated hybrid LCA approach which overcomes boundary limitations of a process approach, by combining the process LCA inventories and Environmental Input-Output (EIO) data, 29,31,35 to evaluate the environmental profile of a laboratory-based PZT versus KNN piezoelectric materials. In the subsections that follows, details of how process LCA and EIO are combined to form hybrid LCA is presented.…”

“…Process-based analysis is more suitable for adoption in instances where the flows of a range of goods and services for specific processes, products, or chains of manufacturing are easy to trace and track at a physical level 31 . It works by establishing a system boundary dictated by the scope of the study, accounting for individual emissions contributions within the system.…”

“…29,37 However, the method suffer from a number of well-recognised limitations, including proportionality and homogeneity assumption, conversion of economic quantities into physical quantities and less specific due to aggregation of a range of activities in one sector. [36][37][38][39][40] Integration of the two methods via a hybrid method augments the specificity of process LCA with the inclusivity of EIO 31,35,[41][42][43] ; hence hybrid LCA models can be implemented in practice to broaden the system boundary whilst complying with ISO standards. 41,44 In the hybrid LCA system, process LCA is interlinked with the complete supply chain system boundary provided by EIO model, which captures the entire economic supply chain along with its sectorial changes and production and consumption patterns.…”