Carbon footprints from dairying are modest

By Jim Paulson, University of Minnesota Extension

ST. PAUL, Minn. (1/26/2009)—Going "green" is doing what is environmentally beneficial, and part of the green discussion is carbon footprint.

A carbon footprint is a measure of environmental impact of the amount of greenhouse gases produced, measured in units of carbon dioxide. The Environmental Protection Agency (EPA) estimates that 6.3 percent of the total greenhouse gas comes from agriculture, with 20 percent of this from production agriculture and 80 percent from processing and transporting food.

In general, greenhouse gases associated with dairy farming are carbon dioxide, methane (natural gas) and nitrous oxide. The two gases of greatest concern are methane and nitrous oxide. Methane comes from rumination by cows and from manure breakdown. It is the methane from manure digestion that is the fuel for electrical generators in on-farm digesters. Methane is very stable and unless burned, can remain in the atmosphere for years. Nitrous oxide comes mainly from manure and nitrogen fertilizer. The EPA estimates that 21 percent of the methane comes from ruminants and 8 percent from manure. Similar amounts of methane come from landfills (24 percent), and natural gas and petroleum systems (26 percent).

Methane gets a lot of attention because it is up to 21 times more potent than CO2 at trapping heat in the atmosphere. This has caused people to look at ruminants as contributors of methane to the atmosphere. However, according to the U.S. Fish and Wildlife Service, the size of the bison herd on the North American continent several hundred years ago is estimated to have been 30 to 75 million head, likely at the upper end. This compares with the current U.S. cattle inventory of all types of just fewer than 100 million head. Since bison were forage consuming ruminants like cattle, we would expect similar methane production.

What is the carbon footprint in making milk? A recent Wall Street Journal article stated that Dallas-based National Dairy Holdings found the carbon footprint of a gallon of milk in a plastic jug to be either 6.19 or 7.59 pounds of carbon dioxide, depending on how it was transported to the store. This included the growing of the feed all the way to delivery of the milk to the store.

Compare this to the car you drive: on the average, it produces a pound of carbon dioxide for every mile it travels. When doing laundry, about a pound per load (not including drying) adds 4.4 pounds.

How do these issues fit your farm or household? Today's consumers want to make a connection to what they eat and feel good about it.

Any use of this article must include the byline or following credit line:
Jim Paulson is a dairy educator with University of Minnesota Extension.

Media Contact: Catherine Dehdashti, U of M Extension (612) 625-0237, ced@umn.edu

URL: http:// www.extension.umn.edu/extensionnews/2009/modest-dairying-carbon-footprint.html  This page was updated Jan. 26, 2009 .
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