Environmental Trade-Offs of Methane-Related Farm Typologies in Mexican Smallholder Dairy Systems: A Life Cycle Assessment

Smallholder dairy farms are central to rural livelihoods in Latin America, yet feeding strategies can shift environmental burdens across climate, land, and water dimensions. This study integrated cluster analysis and life cycle assessment to identify methane-related feeding typologies and assess their environmental trade-offs in smallholder dairy farms in the Mexican highlands. Twenty-nine farms from two dairy regions were classified by k-means clustering into two methane-emission-related farm typologies, which were subsequently characterized by their observed feeding profiles: conserved-forage-dominant (Cluster 1, n = 17) and green-forage-dominant (Cluster 2, n = 12). Their environmental performance was assessed with a cradle-to-farm gate life cycle assessment following ISO 14040/14044 and ReCiPe 2016 Midpoint across 18 impact categories. Feed production and ration supply were the main hotspots, contributing 72 to 100% of the total impacts. Global warming potential averaged 2.29 and 2.47 kg CO2-eq per kg of raw milk in Clusters 1 and 2, respectively. Within the study sample, exploratory comparisons indicated higher marine eutrophication and land use in Cluster 1, whereas Cluster 2 showed higher fine particulate matter formation, terrestrial acidification, terrestrial ecotoxicity, and human carcinogenic toxicity (nominal p < 0.05). These potential trade-offs require validation in larger cohorts and with more geographically representative inventories. These findings show that similar milk outputs can arise from distinct feeding pathways with different environmental trade-offs and that greater reliance on fresh forage does not necessarily imply a more favorable environmental profile. Cluster-based characterization offers a practical basis for improving feed sourcing and ration design in dairy systems facing resource constraints.