Critical analysis of resource-driven Exergetic Life Cycle Assessment (ELCA) versus emission-driven LCA of a dairy farm. Towards ecological-economic analysis
Livestock farming has increasingly been studied using Life Cycle Assessment (LCA) with a main focus on emission-related impacts (de Vries and De Boer, 2010). Many livestock systems, however, have become high input/high output systems, which makes resource-based analysis more relevant in order to support whole-farm strategies to improve both the economic and ecological performance. A resource footprint can be calculated by conducting an Exergetic Life Cycle Assessment (ELCA), which combines Exergy Analysis (EA) and LCA (De Meester et al., 2009). EA is a thermodynamics-based accounting method for the consumption of resources (materials and energy) that quantifies them on one common scale (Joules of exergy) (Szargut et al., 1988). The similar system logic between an EA (exergy values) and an economic analysis (monetary values) enables an integrated ecological-economic assessment.
Our study aims (i) to critically analyse the combined application of a resource-driven ELCA and an emission-driven LCA and (ii) to explore the possibilities of linking ELCA and/or LCA with an economic analysis to enhance sustainable development of livestock systems.
We performed a case study on an intensive dairy farm in Flanders starting from a thorough process-based input/output analysis of the farm. The resource footprint is quantified using the Cumulative Exergy Extraction from the Natural Environment method (CEENE) (Dewulf et al., 2007). Emission-related impacts, such as climate change, eutrophication and acidification, are assessed using the ReCiPe method (Goedkoop et al., 2013). Economic analysis is based on the dairy farm’s accountancies.
The CEENE assessment showed that feed dominates the total resource use across the life cycle (92%). This was mainly due to land use for biomass production. Off-farm land occupation accounted for 46% of total land use. Land (80% of total CEENE) and fossils (14%) are the most utilised resources. Fossils were predominantly used for feed supply (85%) in a direct and indirect way. On-farm water use accounted for 51% of total blue water (ground water and fresh surface water) use across the life cycle. The calculations of the emission-related impacts and the economic analysis are in progress.
ELCA shows that feed supply is the dominating input in terms of total resource use. From the preliminary economic analysis, a similar dominance of feed is seen in the cost structure of milk production. Substitution between concentrated feed and forage is expected to be a key farming strategy for an ecologically and economically optimized milk production. However, existing LCA analyses of dairy systems (IDF, 2009) indicate that feed is less dominant in the carbon footprint. The forthcoming results of LCA and economics will further concretize which and how ecological and economic information should be linked in an economic-ecological trade-off analysis to enhance sustainable development of livestock systems.
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