An economic and environmental optimization model for pig-fattening units using a carbon tax

International audienceEconomic and environmental sustainability is a major concern for pig production systems (PPS). Previous studies showed that formulating low-impact diets using a carbon tax could decrease the climate change (CC) impact of pigfattening units. However, they did not consider the effect of interactions between feed formulas, feeding and shipping strategies (FFSS) on the environmental impacts of pig production. Consequently, the objective of this study was to investigate effects of a carbon tax on economically optimized FFSS and the resulting economic and environmental performances. We used a bi-level optimization model in which the upper level represents a bioeconomic model that simulates the growth of a batch of pigs and optimizes both the amino acid contents in growing and finishing feeds, the level of feed supply, and the shipping strategy. The lower level represents a linear least-cost feed formulation. The model’s behaviour was investigated in four contexts of recent feed and pork prices (low price: L and high price: H; feed: F and pork: P) at different carbon tax level. Optimized FFSS were highly sensitive to both the economic context and the carbon tax level. Without carbon tax, CC impact was lower in LF-LP than in the other economic contexts. With HF, the optimal amino acid contents and feed supply decreased as tax level increased. With LF, the optimal amino acid contents in the finishing diet increased as tax level increased, to improve feed conversion ratio. With increasing tax level, peas and cereal by-products were replaced with cereals and oil meals in pig diets. The highest potential of CC mitigation was obtained with HF-LP context, whereas LF-LP context had the lowest potential of CC mitigation because it resulted in low CC impact, even without application of a carbon tax. Optimizing both levels (FFSS) while applying a carbon tax decreased CC by up to 43% and saved up to 26% of income compared to FFSS optimized without carbon tax. This model provides a valuable tool to investigate the adaptation potential of PPS to the application of a carbon tax