Methane production inventory between 1960-2020 in the Finnish dairy sector and the future mitigation scenarios

Enteric methane (CH4) represents about half of the climatic footprint of milk production in Finland. Methane is generated from the surplus hydrogen produced during the anaerobic feed digestion process in the rumen. Methane intensity per liter of energy corrected milk (g CH4 kg-1 ECM) is a function of the number of cows, milk yield (MY), replacement rate (RR), and the diet composition. This study aimed to model and report the inventory of CH4 from milk production in Finland between 1960 and 2020. Furthermore, we report the potential future scenarios of CH4 mitigation strategies based on the further development in MY and feed efficiency with constant or changing BW of cows. The diet composition of cattle was formulated for 5-year periods according to feed consumption statistics and the current metabolizable energy (ME) requirements for dairy cattle. The CH4 production from cattle was simulated using the formulated diets with the Nordic dairy cow model Karoline. The future CH4 mitigation scenarios of increased MY and improved feed efficiency were simulated using Lypsikki?? dairy farm model. During the inventory period, the number of cows (1000) decreased from 1150 to less than 258, and MY increased three-fold. The total milk and CH4 production peaked in 1965 being 3650 and 110 million kg per year and decreased to 2300 and 48 million kg per year in 2020, respectively. Consequently, decreased number of cows and increased MY reduced the total CH4 production by 56%. In addition, CH4 intensity improved by 36% during the inventory period. Of the future scenarios, increased MY and improved feed efficiency had a substantial potential to improve CH4 intensity. In both scenarios maintaining the current BW of cows resulted in higher mitigation potential. We conclude that selecting more efficient animals has a significant CH4 mitigation potential.