Life cycle assessment of 36 dairy farms with by-product feeding in Southwestern China

Abstract In Southwestern China, dairy farms utilized by-product feeds in dairy production and surplus calves were kept for producing beef as a by-product. However, it is unclear how the environmental impacts are in such dairy production system. This study evaluated, for the first time, the global warming potential (GWP), acidification potential (AP), eutrophication potential (EP) and energy consumption (EC) of 36 intensive dairy farms by life cycle assessment (LCA) in China, and investigated the effects of the feeding patterns on the environmental impacts by a principal component analysis (PCA). The results of the LCA showed that the impacts of beef production by surplus calves and culled cows accounted for 43, 41, 41 and 40% of the total GWP, AP, EP and EC values, respectively, despite the fact that beef was considered as a by-product in the dairy system. Five feeding patterns were distinguished as principal components (PCs): vegetable residue-based concentrate feeding (PC1), beverage by-product feeding (PC2), corn grain-stover feeding (PC3), corn silage-stover feeding (PC4) and rice straw-based brewers' grain feeding (PC5). The results of the PCA indicated that the farms utilizing by-product feeds purchased from companies near the study area had relatively low environmental impacts. In contrast, the farms that managed cows without precise nutritional planning showed relatively high impacts in terms of GWP, AP, EP and EC. Other impact categories, such as abiotic depletion and land use, would be considered for a complete assessment of dairy production in future studies. The consequences of this study could have a certain reference value on making policy/planning for developing dairy-beef production in China.