Fonterra has completed an 18-month project measuring the carbon footprint of its milk, but is not issuing the full results.
The company, which paid for the majority of the study, is issuing only a media release and details of the methodology.
The Ministry of Agriculture & Forestry put $225,000 towards the study, which was undertaken by the University of New South Wales, Scion and AgResearch.
It found that a carbon footprint of 940 grams of carbon dioxide is created per litre of milk.
Some 85% of the greenhouse gasses were emitted on the farm, 10% during processing and manufacturing and 5% in distribution.
Fonterra, which produces about 15 billion litres of milk a year, is not releasing the entire report, citing commercial confidentiality.
But spokesperson John Hutchings says the company will release details about the study's methodology, so other dairy companies can follow the same method.
Fonterra says the study identifies where emissions sit in the supply chain and will help to target efforts to reduce them.