Carbon footprint of cheese produced on milk from Holstein and Jersey cows fed hay differing in herb content

Summary

The objective of the study was to assess the impact on emission of green house gasses (GHG) from production of cheese based on milk from different type of hay and breed of cows, and as an integrated part to give figures for emission from production of hay in climate lees favorable for on field hay drying. Emission of GHG was estimate using life cycle assessment with kg of milk and kg of energy corrected milk (ECM) delivered to the dairy factory, and kg of cheese at the retailor level in Denmark as functional units. Allocation at farm gate, between milk and meat, was made by biological relation between energy requirement to milk and meat production or economic allocation and at the dairy between cheese and whey using either economic allocation or system expansion. Inventory data was based on farm, herd and plant production data from commercial farms participation in on farm research activities with controlled production of hay, in combination with production information from cheese processing and literature estimates, all build into a static model. There was no effect of proportion of herbs in the hay on the emission of GHG, but an effect of breed. The emission per kg cheese was lowest from Jersey, 9.88 kg CO2 eq. per kg cheese, compared to 12.1 and 12.7 from two Holstein herds, although the emission per kg ECM at farm gate was highest from Jersey, but this was more than offset by higher utilization of Jersey milk for cheese. The emission from farm to retailor was below 10 % of the total emission, with the largest contribution from use of energy during manufacturing at the dairy, including storage. Methane with approximately 50 % of all emission was the major source, followed by emission associated to production of feed and rising of heifers. Use of energy for hay drying adds 7-8 % to the emission and soil carbon change in average 3 %, with some variation between farms. The sensitivity analysis showed a potential 6-7 % lower emission of methane due to the increased amount of herbs, while a higher amount of roots due to herbs only has marginal effect on soil carbon at product level. Assuming the same feed conversion in Holstein as in Jersey reduced the different due to breed in emission per kg cheese, but still with a lower emission from Jersey, which illustrate the positive effect of Jersey milk composition on cheese production efficiency.