Dairy farming is known to emit greenhouse gases (GHG), both from direct and indirect emission sources. Carbon dioxide (CO2) is emitted from the combustion of deep sequestered fossil fuel while non/temporarily sequestered, biologically mediated, methane (CH4) and nitrous oxide (N2O) are emitted by various sources, most notably by cattle, feed production, and manure management.
Dairy farmers and their key advisors, the balance of the dairy value chain, policy makers, government officials, non-governmental organizations (NGOs), and astute consumers value best available information about the greenhouse gas (GHG) emissions associated with milk production. In 2020, the Innovation Center for US Dairy (IC) set three 2050 environmental stewardship goals spanning from cradle to processor gate (i.e., milk production and milk processing), including GHG neutrality. Further, the IC committed to outwardly reporting on progress towards the goals every five years starting in 2025.
What Did We Do?
Work focused on the cradle to farm gate (milk production) segment of the overall GHG neutrality goal. A list of considerations deemed important to conduct a robust US dairy GHG analysis was developed and evaluated. The most important key considerations determined were geographic-driven factors and assessment focused approach (i.e., sampling farm population, not sampling). Boundaries for the four areas making up a cradle to farm gate categories for analysis – Cattle (Enteric), Feed, Manure, and Energy – were developed based in part on understanding of where available data is housed and managed by farmers and their custom operators and following Life Cycle Assessment (LCA) practices.
What Have We Learned?
The most important lesson learned was that sampling a farm population and scaling results to represent the US dairy industry GHG emission footprint cannot be used for multiple reasons. First, classical statistics requires a sample needs to be normally distributed about the mean – herd size is not normally distributed among farm size, 80 % cows owned by 20% of the farms and milk production is higher, between 3,000 and 5,000 lbs./cow annually, for larger herds. Second, the data needed from every farm doesn’t exist today. Third, random sampling of MILK and COWS is required, however, farmers are surveyed. Fourth, accurate emission results require a percentage of cows surveyed and the percentage of milk surveyed to be the same; however, the estimated probably is less than 0.0001 that this would occur (once in every 10,000 years if annual surveys were conducted). Lastly, analysis showed that unavoidable and unpredictable error resulted when scaling up sample analysis results to the US dairy population, meaning that a reported carbon dioxide equivalent (CO2e) value would have tremendous uncertainty in direction and magnitude. This is especially challenging when measuring progress toward the 2050 GHG neutrality goal; a population sampling and scaling based approached can result in higher calculated emissions in five years over a current value, even though many farms made notable changes to reduce GHG emissions.
Leaders of the US dairy industry were educated on the challenges of farm sampling and scaling. As a result, the decision was made to approach quantification of the progress toward the 2050 GHG neutrality goal using an approach that removes the need for scaling. That approach is called USDA Cow and Milk Data Focused approach.
Measurement of US dairy’s progress towards its 2050 GHG neutrality goal will be made using the USDA Cow and Milk Data Focused approach; first report on progress due in 2025.
Curt A. Gooch, Sustainable Dairy Product Owner, Land O’Lakes – Truterra
Corresponding author email address
Roger Cady, Freelance Sustainability Consultant (Retired from industry)
Dairy Management Incorporated and the Innovation Center for US Dairy Environmental Stewardship Committee
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