Going “green” is the “in thing” for our world today. But just what does that mean? What is a carbon footprint?

It might also be things like reducing electricity use on the farm through lighting types or fixtures, variable speed vacuum pumps, use of plate coolers or other similar investments. Recycling is also a “green” practice. Many homes recycle aluminum, plastics and paper. Most farms have not been involved in recycling other than milk house detergent containers and totes. Recently there has been recycling of silage bag plastics, but this is limited due to distance to the recycling center.

Another term that is frequently being used in 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. Greenhouse gases are given their name because of their effect on global warming. Greenhouse gases hold in heat in the earth’s atmosphere. Much debate goes on about whether this is real or a natural cycle.

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 the processing and transportation of food. In general, greenhouse gases associated with dairy farming are carbon dioxide (CO2), methane (CH4, natural gas) and nitrous oxide (N2O). Carbon dioxide is cycled in the natural process of photosynthesis.

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? Different studies have come up with different estimates. 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. Or doing laundry, about a pound per load not including drying, which adds 4.4 pounds. Another movement gaining momentum is buying local foods.

There are many reasons for this. Food is fresher and of known origins. But it also saves on transportation costs and as such, reduces the carbon footprint. Buying local and unprocessed foods would greatly reduce the impact as well as supporting a local economy. Another term that is becoming more of our everyday conversation is “sustainable.”

The USDA has a five-part definition for a sustainable farm:
1. It must provide human food and fiber needs.
2. It must enhance the environmental quality and natural resource base upon which the agricultural economy depends.
3. It needs to make the most efficient use of non-renewable resources and on-farm resources and try to integrate, where appropriate, natural biological cycles and controls.
4. It needs to be economically viable.
5. It needs to enhance the quality of life for the farmers and society as a whole.

How do these definitions fit your farm? Today’s consumer and our society want to make a connection to what they eat and feel good about it. These will be issues we will be addressing in the future in agriculture.

—Excerpts from University of Minnesota Dairy Star, November 2008