The carbon footprint of milk during the conversion from conventional to organic production on a dairy farm in central Germany

Dairy products play an important role in human nutrition, but at the same time, the dairy sector is a major contributor to global warming. The conversion from conventional to organic milk production could reduce the carbon footprint due to the elimination of synthetic fertilizers and strong reliance on closed on-farm nutrient cycling. We present one of the first studies to comprehensively estimate the climate-change impacts of the conversion to organic production of a large-scale dairy operation in central Germany. We used detailed farm data and a carbon footprint approach based on the IPCC tier-2 methodology to estimate greenhouse gas (GHG) emissions associated with feed production, animal husbandry, and animal rearing. Our results show that the carbon footprint per kg of energy-corrected milk (ECM) decreased by 9% during the first year of conversion to organic milk production. Conversely, livestock emissions per kg ECM increased by 12% in the first conversion year due to the increase in methane emissions from enteric fermentation, but this increase was more than offset by the decrease in emissions from feed production. Emissions from internal and external feed production per kg ECM decreased by 17% and 29%, respectively. Our study helps to understand how individual emission sources change as a result of a farm’s conversion to organic production. This research is important and timely, as the European Union is pursuing ambitious goals to increase the area under organic farming, although the impact of the conversion period on GHG emissions has been insufficiently studied.