From Grass to Glass: How U.S. Dairy is Working to Reduce Greenhouse Gas

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Green Pastures…and Green Farming



Richard Williamson

Across industries and around the world, the search for sustainability is a never-ending process. But one of the most sustainable systems is right in front of us: the dairy farm.

Dairy farming is inherently one of the most sustainable forms of agriculture because of its ability to naturally recycle nutrients between people, animals and plants. Having four stomachs means a cow can recycle food that people can’t eat, such as grass, cotton seed, or citrus pulp. She converts that into an average of 144 servings of nutrient-rich milk per day, and manure that can be used to grow more crops for people and animals. Across the United States, dairy farms large and small are intent on optimizing this natural nutrient cycle. 

Closed-loop farming


Dairy farms are ideal for adopting a “closed-loop” approach to farming:  a process where the nutrients needed to grow crops and feed animals are recycled within the system, and minimal external inputs – such as fossil fuel-based fertilizers -- are required.

Dairy farmers routinely recycle cow manure as fertilizer to grow the feed for cows. Taking the closed loop system a step further, extra cow manure and commercial food waste, both of which release methane gas when they decompose, are used as feedstock for a methane digester to produce clean renewable energy, nutrient-rich liquid fertilizer and fiber for use as bedding for the cows or as a garden soil amendment. This eases the footprint from manure, one of the largest potential sources of environmental impact in modern industrial farming. 

Running a dairy farm entirely within a closed-loop system is the ideal, if not always 100 percent achievable. Most dairy farms need to import at least some portion of their animal feed. It is not uncommon for the majority of that feed, in the form of forage, to come from within ten miles of the dairy. In this way, closed-loop farming can extend beyond a single operation to neighboring farms. Manure can be “shared among neighbors” for fertilizer, lessening the need for additional nitrogen inputs within a local agricultural community.

Carbon hoofprint

While many sustainability efforts and agreements get bogged down in politics, the USDA and the Innovation Center for U.S. Dairy have been a model of cooperation, signing a Memorandum of Understanding expressing USDA’s support for the dairy industry’s voluntary  goal of reducing greenhouse gas (GHG) emissions across the dairy industry by 25 percent by 2020.

Researchers Dale E. Bauman of Cornell and Judith L. Capper of Washington State University have collaborated to study the challenges and opportunities of dairy sustainability. To get a sense of the progress made in carbon impact, Bauman and Capper employed a “whole system model” to quantify the environmental impact of milk production on dairy farms in the United States. In 1944, the average cow had a carbon "hoofprint," if you will, half that of the higher producing cow found on today’s dairy farm.

This single statistic taken out of context may, as Bauman and Capper note in their report, obscure the efficiencies gained in milk production in the last century.  As Bauman and Capper also note, those efficiencies have dramatically reduced the carbon footprint per gallon of milk produced– a more informative measure.