In what is being hailed as good news, the Food and Agriculture Organization (FAO) of the United Nations now estimates the worldwide dairy industry's contribution to global greenhouse gas (GHG) emissions to be just 2.7%. If you add in cull cows and dairy beef, the total is 4.1%.
FAO estimates GHG per kilogram of milk to be 2.4 kg of CO2 equivalent and that North American herds produce 1.3 kg of CO2 equivalent per kilogram of milk. About 1 kg comes from milk production, the remainder from processing milk into retail fluid and other products.
Frank Mitloehner, an air quality researcher with the University of California, Davis, was critical of FAO's earlier estimate that livestock contributed 18% of GHG emissions. When he pointed out that the comparison was to emissions from transportation and did not include other emissions such as from power generation, FAO acknowledged its error.
"I'm very pleased with the change of tone and content in this latest report,” Mitloehner told Dairy Today.
Greg Thoma, an engineer with the University of Arkansas, agrees. "Results are strongly correlated to production efficiency,” he says. "If you have high feed conversion efficiency, you produce more milk and less manure per gallon of milk.”
The FAO report shows that grazing systems produce, on average, 2.72 kg of CO2 equivalent per kilogram of milk. Herds fed highly digestible stored feeds have 35% lower emissions. "This is mainly driven by two factors: the higher digestibility of the animal's feed and the higher milk productivity levels,” the report says.
Developing countries have an opportunity to reduce emissions by growing, grazing and feeding more digestible forages, FAO says. In North America, 15% to 20% of methane emissions come from manure storage. So methane digestion and energy production is one way to decrease GHG emissions here.
- June/July 2010