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Background, Aim and Scope:
Different methodologies within LCA are used to assess the environmental burden of milk production. A strong connection exists between choice of methodology and choice of how to handle co-products. A need exists to evaluate the effect of choices within LCA. The main goal of this study was to evaluate the effectiveness of attributional and consequential LCA by comparing attributional and consequential LCA results for an average conventional milk production system in the Netherlands.
Materials and Methods:
Attributional LCA (ALCA) describes the pollution and resource flows within a chosen system attributed to the delivery of a specified amount of the functional unit. Consequential LCA (CLCA) estimates how pollution and resource flows within a system change in response to a change in output of functional units. For an average Dutch conventional milk production system an ALCA and a CLCA were performed. Impact categories included in the analyses were: land use, energy use, climate change, acidification and eutrophication. Within ALCA different ways to handle co-products were applied; mass and economic allocation, and system expansion. Within CLCA only system expansion was applied. Evaluation of the effectiveness of both methodologies was based on an assessment on their relevance, comprehensibility, quality and availability of data.
Results:
When applying CLCA or ALCA different systems are modelled and conclusively, hotspots differ. The main identified hotspots were the same, but the other identified hotspots differed in contributions, order of hotspots and elements. The degree of understanding is educational-related and depends on the background of the receiver. On the one hand CLCA seems more sensitive to uncertainties due to the inclusion of market prospects, on the other hand the usage of allocation factors is an artificial way of dividing the environmental burden between products. The data availability is similar.When comparing outcomes between CLCA and ALCA (mass and economic allocation), all total values of CLCA were lower. Results showed that when using economic or mass allocation within ALCA total environmental burdens were influenced only slightly. Using system expansion within ALCA gave negative values for the impact categories land use, climate change and eutrophication.
Discussion:
The identified environmental hotspots of conventional milk are not the same within ALCA and CLCA, because different systems are modelled. When using economic or mass allocation only total environmental burdens were influenced slightly. Applying system expansion within ALCA inserts inconsistencies, because system expansion requires consequential thinking. Expanding a system based on average processes, using average avoided processes based on market analyses inserts this inconsistency.
Conclusions:
Results showed it is possible to perform both ALCA and CLCA of milk and it is possible to perform different ways of how to handle co-products within ALCA. These methodological choices, however, result in different outcomes, because different systems are modelled.
Recommendations and
Perspectives:
We recommend LCA practitioners to better distinguish between ALCA and CLCA in applied studies to reach a higher degree of transparency. We also recommend to address the distinction between ALCA and CLCA in recommendations of how to handle co-products within the ISO guidelines. We also recommend LCA practitioners of different research areas to perform similar case studies to address differences between ALCA and CLCA.
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