Use of organic waste streams to reduce the carbon footprint of New Zealand milk

Life Cycle Assessment was undertaken to determine the impact of replacing purchased feeds and nitrogen fertiliser with New Zealand-sourced organic waste streams, on the cradle-to-farm-gate carbon footprint of a dairy farm. Five scenarios were assessed: 1) average New Zealand dairy farm, 2) supplementary feeds sourced from food waste, 3) mineral fertiliser replaced with chicken manure, 4) mineral fertiliser replaced with pig manure, 5) a combination of scenario 2 and 3. Diets in each scenario had the same total metabolisable energy and nitrogen content. Organic fertiliser was applied to ensure the same total nitrogen application per hectare. Replacing purchased feeds with waste from the food industry reduced the carbon footprint by 9%, while replacing synthetic nitrogen fertiliser with chicken or pig manure resulted in a reduction of 1%. Although this has shown the potential to reduce the carbon footprint of New Zealand milk while also reducing reliance on mineral fertilisers and imported feed, further work is required to determine feasibility and broader impacts.