Modelling the environmental impacts of pig farming systems and the potential of nutritional solutions to mitigate them

Abstract

The overall aim of this thesis was to model the environmental impacts of pig farming systems in Canada using Life Cycle Assessment (LCA), and to quantify the potential of nutritional solutions to reduce these. To achieve this, methodological challenges regarding co-product allocation, modelling uncertainty in agricultural LCA and how to formulate pig diets for environmental impact objectives needed to be resolved. The options for co-product allocation in LCA studies of agricultural systems were evaluated and it was concluded that economic allocation was the methodology that could be adopted most consistently throughout the feed supply chain in livestock LCA models. A LCA model which quantified the environmental impact of Canadian pig farming systems, for multiple impact categories, was developed for the first time. A new approach to uncertainty analysis for the LCA of livestock systems using parallel Monte-Carlo simulations was also developed. The potential of including specific by-products from the human food and bio-ethanol supply chains in pig diets to reduce environmental impacts was investigated. Wheat shorts and bakery meal were found to reduce the environmental impact of the system in the scenarios tested. Further integration of diet formulation techniques with the LCA model allowed pig diets to be optimised explicitly to minimise environmental impact, while accounting for the effect of diets on nutrient excretion and the effect of energy density on feed intake in order to determine the optimum energy density of pig diets for different objectives. The potential effect of three environmental taxes, a carbon tax, and taxes on spreading N and P in manure respectively, on formulating pig diets and their implications for environmental impact were also modelled. The carbon tax was the only tax which consistently caused significant reductions in any of the impact categories tested in the LCA. Overall, novel methodologies for modelling uncertainty in livestock LCA and formulating pig diets to minimise environmental impacts were developed. Using the latter, pig diets were formulated to reduce the environmental impacts of the production system for multiple impact categories simultaneously for the first time. These methods allowed the potential of dietary alterations to reduce the environmental impact of pig farming systems to be investigated systematically, and have wider applications for LCA modelling in livestock systems.