Scientists have produced the first detailed data on how large-scale dairy facilities – cows, equipment, buildings, and all – create greenhouse gases, which are believed by the majority of climate scientists to be causing Earth to grow warmer. Agricultural Research Service (ARS) soil scientist April Leytem led the year-long project, which involved monitoring the emissions of ammonia, carbon dioxide, methane and nitrous oxide from a commercial dairy with 10,000 milk cows in southern Idaho.
The results suggested that, on average, the facility and animals generated some 37,000 pounds of emissions daily. That’s 3,582 pounds of ammonia, 33,162 pounds of methane and 410 pounds of nitrous oxide every day.
The Idaho cows in this study were mostly mature Holsteins. Their home facility had 20 open-lot pens, two milking parlors, a hospital barn, a maternity barn, a manure solid separator, a 25-acre wastewater storage pond and a 25-acre compost yard.
Leytem, who in 2008 was presented with an ARS award for her work in phosphorus cycling in the environment, said:
We’ve calculated some of the first on-farm emission rates for western large-scale dairies, along with emissions per cow and per unit of milk production. We’re performing these studies on working commercial dairies, not on experimental farms.
The team set out to calculate the emission rates of the four gases from three areas on the dairy facility: the open lots, the wastewater pond, and the compost yard. After they set up their instrumentation, they collected concentration data continuously for two to three days each month, along with air temperature, barometric pressure, wind direction and wind speed. With these data, Leytem’s team calculated the average daily emissions for each source area for each month.
The results indicated that, on average, the facility and the animals generated 3,582 pounds of ammonia, 33,162 pounds of methane and 410 pounds of nitrous oxide every day. The open lot areas generated 78 percent of the facility’s ammonia, 80 percent of its carbon dioxide, 57 percent of its nitrous oxide, and 74 percent of the facility’s methane emissions during the spring.
Generally, the emission of ammonia, carbon dioxide, and nitrous oxide from the open lots was lower during the late evening and early morning, and then increased throughout the day to peak late in the day. These daily fluctuations paralleled patterns in wind speed, air temperature and livestock activity, all of which generally increased during the day.
Emissions of ammonia, methane, and carbon dioxide from the wastewater pond and the compost were also lower in the late evening and early morning and increased during the day. Ammonia, methane, and carbon dioxide emissions from the compost peaked during June when the compost was frequently turned and when new manure was being added to the windrows. Methane emissions from the wastewater pond were lowest in April, when seasonally cooler temperatures prevailed, but peaked during October as temperatures rose.
Dr. Leytem worked with other scientists at the ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho. Results of the study appear in the July 2011 issue of Agricultural Research magazine.
Bottom line: April Leytem and her team at at the ARS Northwest Irrigation and Soils Research Laboratory have produced the first detailed data on how large-scale dairy facilities create greenhouse gases. They monitored greenhouse gas emissions from a dairy farm in Idaho, with 10,000 milk cows. The farm generated 37,000 pounds of emissions daily. Results of the study appear in the July 2011 issue of the USDA Agricultural Research magazine.