Resource use assessment of an agricultural system from a life cycle perspective – a dairy farm as case study

Abstract

Despite the great pressure on global natural resources, few LCA studies focus on total resource consumption and the efficiency of the use of those resources. Moreover, a total resource use assessment for agricultural systems is highly relevant because many of these systems have become high input/high output systems in order to achieve higher productivity. In this study, we propose a framework to evaluate total resource consumption of agricultural systems at the process level using an Exergy Analysis (EA) and at the life cycle level using an Exergetic Life Cycle Assessment (ELCA). We evaluate the applicability and usefulness of this approach based on a case study of an intensive confinement-based dairy farm in the region of Flanders, Belgium. The EA showed that more than half of the resources consumed by the dairy farm's herd was irreversibly lost, as a consequence of the second law of thermodynamics. The remaining went for almost two-thirds to manure (54%) and methane emissions (9%), while only one-third flowed to end-products, i.e. milk (32%) and the animals awaiting slaughter (2%). The ELCA identified the feed supply as the most demanding part of the dairy production chain by far, representing 93% of the resource footprint. Overall, concentrates were on average 2.5 times more resource-intensive per kg dry matter than roughages, while wet by-products were 34% and 73% less resource-intensive than roughages and concentrates, respectively. Mainly land (77%) and fossil resources (17%) were required throughout the life cycle. About 36% of the occupied land (in terms of m2*year) was located off-farm. Slightly less than one-quarter of the fossil resources were used on-farm as fuel and electricity. The on-farm use of groundwater accounted for about half of the total blue water use across the life cycle. With this paper, we show the usefulness of the proposed framework to evaluate total resource consumption of dairy farms and to identify on-farm and off-farm improvement opportunities. This framework has potential to support research on whole-farm improvement strategies such as pasture-based systems and low-input farming, and to compare populations of contrasting milk production systems.