Accounting for farm diversity in Life Cycle Assessment studies - the case of poultry production in a tropical island

The farm is the most influential stage of agricultural production because farming practices affect both pre-farm and on-farm environmental impacts. Since farm diversity is not usually taken into consideration, it is legitimate to question the interest of including it in Life Cycle Assessment (LCA) studies. This work explores several approaches to modelling the farm stage when assessing the environmental impact of an agricultural supply chain in a context with variable farm performances. A LCA of a poultry supply chain was applied from cradle-to-slaughterhouse gate. The first approach is a classical one in which farm diversity is not taken into account and an average farm is constructed on the basis of weighted average farm characteristics. The second approach distinguishes four farm types identified by cluster analysis, and four LCA were performed according to these farm types. Farm types were distinguished based on their consumption of inputs and the type of ventilation of the farm buildings. Results indicate that the classical approach is sufficient to highlight problem hotspots and to identify promising mitigation measures. Reducing the transport distance of imported maize, improving feed conversion efficiency and anaerobic digestion of slaughterhouse animal wastes were identified as appropriate mitigation measures. As feed production and poultry rearing are the stages with the most impact, distinguishing farm types provides i) insight into farm functioning to better explain the variability of environmental impacts and understand how to reduce them, ii) reduce the uncertainty of results, and iii) provide appropriate recommendations for mitigation measures. Coupling a farm typology with the LCA is particularly useful when farming systems are very diverse like in Reunion Island where the climate varies considerably across the island. (Résumé d'auteur)