As a lover of both dairy products and the environment I am often disheartened to read about the carbon footprint associated with cattle. In an interview with Logan Peterman, Farm Resources Manager for Organic Valley, I quickly realized that when it comes to emissions not all dairy systems are created equal. He expressed that when buying dairy products one can look for products from farmers “that are managing their animals in a way that minimizes the methane and greenhouse gases they produce.”
Methane is an unavoidable outcome of dairy farming, but the amount of methane produced varies greatly depending on a cow’s diet and how manure is managed on the farm. Logan explained that, “the quality of the diet dictates how much [a dairy cow] contributes to global warming.” He sees “[t]he improvement in the diet [as] one of the key pieces [to emission reduction] because it is a win-win.”
In an intensive grazing system farmers optimize diet digestibility by frequently moving their cows through a series of controlled paddocks. Cows are moved often to ensure that the grass they are grazing has the highest level of digestible fiber possible. The more digestible the fiber, the less methane the cows emit. “By keeping the paddock managed between […] not hurting the grass [and it] not getting rank, you are managing the digestibility of the diet.” Logan explained that “this is no small feat” and that farmers have to “manage there timing and the species balance in their fields as well as the nutrition in the soil.” Quality grasses start with a healthy soil, so Logan and his team “are trying to approach it from the soil up and help farmers pack more nutritional punch into their grass, which not only improves their profitability, but also reduces the enteric methane their cows produce.”
Well-managed pastures can also fight climate change by acting as a net carbon sink. The amount of carbon sequestered in the soil by grasses can vary substantially between climatic zones, management, and species. Recent research studying grasslands in a sub-humid climate (like the climate of the Upper Midwest) found that intensive grazing has the ability to sequester a substantial amount of carbon. Researchers believe this is in part because the intensive management strategy keeps the grasses in a very active stage of growth. Keeping paddocks in this active stage is a win for cow digestion and for carbon sequestration–making it pack a double punch in the fight against climate change.
On-farm manure storage decisions also play a large role in greenhouse gas emissions. For instance, during the winter cows will often congregate in a covered, protected barn area. The amount of methane emitted by the collection of manure in this centralized area depends on how it is stored. Logan explained that, “if you store manure in a liquid it releases substantially more greenhouse gases than if you have it in […] what is called a bedding pack where it is mixed with straw, is kind of dry, and breaks down at a slower rate without all of the liquid.” Storing manure in bedding packs creates an environment that makes a good “home for bacteria to compost it down and turn it back into soil.”
When it comes to climatic impact, on-farm management strategies matter. A 2010 study that calculated total methane emissions based on an entire farm’s production practices found that organic farms raising Holsteins produce about one-third less of the total methane per kg of Energy Corrected Milk (ECM) as compared to their conventional counterparts.
As Logan explained, we have a reason to be hopeful because substantial amounts of greenhouse gas reductions are being accomplished on farms that aren’t doing anything revolutionary. These farms are grazing their cows, managing their manure to minimize climate impacts, and are producing highly nutritious milk.
It may not require a revolution to minimize greenhouse gases, but it will require us to grass up in support of farming practices that reduce the climatic impact of cows!
 Other sources of emissions related to dairy production include methane and nitrous oxide from manure, and emissions that result from energy used in feed production, and on-farm energy use. Keep in mind that emissions related to livestock production in most developed countries are dwarfed by emissions associated with energy production and transportation.
 Because of the variability in the nutritional quality of milk, it is important to adjust milk production levels when reporting results to reflect these differences. This method is known as Energy Corrected Milk (ECM).