Consolidating environmental sustainability assessments of livestock systems. An analysis based on the case of Danish pork

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

Abstract

Livestock production systems are central contributors to environmental impacts, including climate change, eutrophication, biodiversity, land degradation, and toxicity-related impacts. With the global consumption of livestock products expected to increase by 2030, achieving environmental sustainability is imperative. The main objective of the Ph.D. was to consolidate environmental sustainability assessment frameworks for livestock products by including a wide range of impact categories in life cycle assessment (LCA). That was considered necessary in identifying environmental trade-offs regarding the implementation of mitigation options. Danish pork production represented the case study for the Ph.D. project.
Firstly, the changes in the management practices in the Danish pork production were investigated by analyzing the development in the environmental impact over ten years. Several biological and technological changes were identified at the farm, feed, and slaughterhouse levels. These included increases in the herd and feed productivity, transition to partly slatted floors in housing conditions, increases in the share of anaerobically digested manure, reductions in the nutrient application rates, use of mineral fertilizers manufactured with new technologies, and increases in the proportion of pig parts used for human consumption. These changes involved decreases in the potential impacts on climate change, eutrophication, acidification, abiotic depletion - fossil fuels, land occupation, and biodiversity to different extents.
Secondly, an LCA framework for assessing toxicity-related impacts for livestock production systems was defined based on the case of Danish pork to account for the use of chemicals in livestock production. That involved quantifying chemicals at feed, farm, and slaughterhouse levels and identifying state-of-the-art methods to be used in assessments. For veterinary pharmaceuticals, a mass balance approach was outlined. For Danish pork, feed production represented the main contributor to toxicity-related impacts, but different emission types were attributed to organic (pesticide emissions) and metal-based substances (heavy metals emissions related to manure application on fields and manufacturing of agrichemicals). Veterinary pharmaceuticals contributed 3% to freshwater ecotoxicity impact, while inorganic substances (e.g., sulphuric acid used in slurry acidification) could not be assessed because of methodological limitations.
Finally, a comprehensive LCA covering seventeen impact categories (including toxicity-related, land use-related, water use-related, and particulate matter impacts) was carried out to identify trade-offs regarding the use of several management practices (e.g., increased herd productivity, chemical air purification in housing facilities, slurry acidification, tent storage of slurry, anaerobic digestion of manure, increased share of by-products in feed rations, use of alternative protein sources – namely fava beans) in Danish slaughter pig farms. The best environmental profile was found for the farm, combining slurry acidification, tent storage of manure, and an increased share of by-products (bread leftovers, potatoes pulp, and rapeseed by-products). However, the toxicity-related impacts regarding using sulphuric acid need clarifying. The management package consisting of slurry acidification, tent storage of manure, and alternative protein sources resulted in lower marine and freshwater eutrophication, acidification, direct land use change, ozone depletion potential, and toxicity-related impacts for organic substances compared to the best performing farm, but higher particulate matter, freshwater eutrophication, resource use – fossils, resource use – minerals and metals, and water use related impacts. Anaerobic digestion of manure positively impacted climate change and resource use – fossils impacts, while chemical air purification technologies only reduced ammonia emissions during housing. The farm focusing on increased herd productivity had low impacts concerning many impact categories, but high impacts on direct land use change, erosion resistance, mechanical filtration, groundwater replenishment, particulate matter, and photochemical ozone formation, determined by the use of soybean meal in feed rations.
The present Ph.D. thesis contributed to the consolidation of environmental sustainability assessments by defining an LCA framework for assessing toxicity-related impacts for livestock production. Furthermore, the assessment of a broad range of impact categories made it possible to identify environmental trade-offs regarding the implementation of different management practices.
OriginalsprogEngelsk
ForlagAarhus Universitet
Antal sider213
StatusUdgivet - jun. 2022

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