Greenhouse gas emissions and feed-food competition on Swiss dairy farms

Negative environmental impacts from livestock need to be reduced. However, animal-sourced proteins will remain important for global food supply, as animals are able to convert biomass not suitable for human consumption to high value proteins. Animals compete directly with human food supply when fed human-edible feedstuffs. Feeding cows with concentrated feeds may decrease GHG-intensity; however, it likely increases feed-food competition. To investigate these conflicts of interest, we assessed GHG emissions and the human edible protein conversion ratio (edible protein in feeds/edible protein in animal products, ePCR) of 87 Swiss dairy cow farms. The GHG emission intensity was 0.70-1.21 kg CO 2 eq (kg energy corrected milk)-1. The ePCR ranged from 0.04 to 1.14. Correlation between GHG-intensity and ePCR was low, implying that low GHG-intensity does not contradict low feed-food competition. Human-edible protein production per kg of CO 2 eq ranged from-4.6 to 32.5 g CP. As a novel approach, we propose to calculate environmental footprints based on net human edible protein supply.