The Institute’s figure of 44 million tonnes of carbon dioxide-equivalent is gaining traction overseas, being used in other research papers.
The research group used an industry-accepted model to calculate the emissions from Fonterra’s global operations (which include New Zealand, Australia and China), says Institute for Agriculture and Trade Policy’s Shefali Sharma.
Dairy farms produce a lot of methane, some nitrous oxide and a little carbon dioxide. The researchers converted methane and nitrous oxide into an equivalent amount of carbon dioxide. (This conversion is a controversial topic, though it’s used across the relevant studies here.)
The Institute team needed to tell the model how much greenhouse gas was produced for each standard litre of milk. They used a number for the Oceania region: the equivalent of 1.88 kilograms of carbon dioxide, on average, for every litre of milk produced. This came from the United Nations’ Food and Agriculture Organisation.