Analysis of sustainability in the pig production chain :life cycle assessment of contrasting scenarios

Abstract

This research investigated the environmental impact of the pig production chain by modelling contrasting scenarios. Life Cycle Analysis (LCA) and scenario analysis methodologies were used to reveal the main opportunities to improve sustainability. Pig production systems were modelled in two countries (The UK and Mexico), each with a standard production system and on alternative system. This gave four scenarios which were different in the degree of integration that exist between pig and crop production and were then specified in detail to allow for comparison of environmental impact. This study used two strategies to analyse the four scenarios: A pre-assessment facilitated the construction of the system boundary and clarified the processes and commodities which should be included in the Life Cycle Inventory (LCI). A hybrid-LCA method combined a detailed collection of environmental burdens (e-burdens) from the main sources (process-LCA) and a broad compilation of e-burdens from indirect sources (Economic Input Output-LCA). The pre-assessment, conducted as a general LCA, explored novel techniques to construct the system boundary and explore the supply chains in detail. This step clarified the importance of the supply chains of different commodities that are used in the pig farm. The importance of previously reported commodities and processes that mainly contribute to the environmental impact, i.e. feed consumption and manure fermentation were confirmed. Novel findings included the importance of the environmental impacts of goods and services, i.e. machinery, equipment, disinfectants and medicines, that have negligible weight in the impact of environmental indicators that are traditionally analysed (global warming, acidification and eutrophication). The inclusion of novel indicators, such as ozone depression and ecotoxicity to water and soil, demonstrated the importance of including in the LCA those commodities and indicators that have been excluded in many previous studies on the sustainability of pig production. Subsequently, the hybrid-LCA method allowed the expansion of the system boundary of the LCA in a detailed evaluation of each scenario. Results showed the UK scenarios to be superior in management of nutrient flow, by manure management and good agricultural practice. Opportunities to capture methane and recycle nutrients for crop production in the Mexican scenarios were highlighted. In contrast, reduction in machinery and equipment use and fuel consumption were the main opportunities which emerged for the UK scenarios. In addition, specific opportunities to reduce the environmental impact of different pig supply chain sectors were identified in each scenario. In conclusion, the EIO-LCA method allowed for an extension of the traditional system boundary of the LCA, to encompass those e-impacts that have not been included in previous studies. The contrasting of different scenarios allowed emphasis to be placed on opportunities to reduce environmental impact of pig production by highlighting the main challenges in each case. This avoids the controversial issue of denoting a set of specific e-impacts that then favour one production system over another.