What is Known about Dairy Cows' Emissions of Greenhouse Gases?


General Reference (not clearly pro or con)
The Food and Agriculture Organization of the United Nations (FAO) wrote in its 2010 report "Greenhouse Gas Emissions from the Dairy Sector: A Life Cycle Assessment," that:

"This study assesses the greenhouse gas (GHG) emissions from the global dairy cattle sector. The overall goal of this report is to provide estimates of GHG emissions associated with milk production and processing for main regions and farming systems of the world...

It focuses on the entire dairy food chain, encompassing the life cycle of dairy products from the production and transport of inputs (fertilizer, pesticide, and feed) for dairy farming, transportation of milk off-farm, dairy processing, the production of packages, and the distribution of products to retailers...

In 2007, the dairy sector emitted 1 969 million tonnes CO2-eq [±26 percent] of which 1 328 million tonnes are attributed to milk...

The global dairy sector contributes 4.0 percent to the total global anthropogenic GHG emissions."

2010 - Food and Agriculture Organization (FAO) of the United Nations 
Greenhouse Gas Emissions from the Dairy Sector: A Life Cycle Assessment (936KB)  

The Food and Agriculture Organization of the United Nations (FAO) wrote in its 2006 report "Livestock's Long Shadow: Environmental Issues and Options," that:

"The livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global...

With rising temperatures, rising sea levels, melting ice caps and glaciers, shifting ocean currents and weather patterns, climate change is the most serious challenge facing the human race.

The livestock sector is a major player, responsible for 18 percent of greenhouse gas emissions measured in CO2 equivalent. This is a higher share than transport...

The sector emits 37 percent of anthropogenic methane (with 23 times the global warming potential (GWP) of CO2) most of that from enteric fermentation by ruminants [such as dairy cows]. It emits 65 percent of anthropogenic nitrous oxide (with 296 times the GWP of CO2 ) the great majority from manure...

In the United States methane from enteric fermentation totaled 5.5 million tones in 2002...overwhelmingly originating from beef and dairy cattle. This was 71 percent of all agricultural emissions and 19 percent of the country's total emissions."

2006 - Food and Agriculture Organization (FAO) of the United Nations 
Livestock's Long Shadow: Environmental Issues and Options (4.75 MB)  

The United States Environmental Protection Agency (EPA) wrote in its Apr. 15, 2007 report "Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2005," that:

"Agricultural activities contribute directly to emissions of greenhouse gases through a variety of processes...

In 2005, the agricultural sector was responsible for emissions of 536.3 teragrams of CO2 equivalent (Tg CO2 Eq.), or 7 percent of total U.S. greenhouse gas emissions. Methane (CH4) and nitrous oxide (N2O) were the primary greenhouse gases emitted by agricultural activities. CH4 emissions from enteric fermentation and manure management represent about 21 percent and 8 percent of total CH4 emissions from anthropogenic activities, respectively. Of all domestic animal types, beef and dairy cattle were by far the largest emitters of CH4."

Apr. 15, 2007 - U.S. Environmental Protection Agency (EPA) 
Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2005 (22.6 MB)  

The United States Department of Energy wrote in its Dec. 2004 report, "Emissions of Greenhouse Gases in the United States 2003," that:

"At an estimated 7.9 million metric tons of methane (182.8 million metric tons carbon dioxide equivalent), methane emissions from agricultural activities in 2003 represent 30.4 percent of total U.S. anthropogenic methane emissions and approximately 2.6 percent of total U.S. greenhouse gas emissions. Ninety-four percent of methane emissions from agricultural activities result from livestock management. Sixty-six percent of these emissions can be traced to enteric fermentation in ruminant animals, and the remainder is attributable to the anaerobic decomposition of livestock wastes...

[C]attle [including beef and dairy cows] account for 95.1 percent of all emissions from enteric fermentation."

Dec. 2004 - United States Department of Energy (DOE) 
Emissions of Greenhouse Gases in the United States 2003 (864 KB)  

BioEnergy Solutions, a company that develops "green energy" from cow manure, published the following in its article "Cow Power," posted on its website (accessed Apr. 30, 2008):

"Farm animals - especially cows - produce large amounts of methane, a greenhouse gas that contributes to global warming.

Emissions from automobiles and factories can be reduced with the installation of sophisticated equipment. But we have yet to see a catalytic converter or scrubbing system that will capture gases generated by cows at, shall we say, the source...

We capture the methane released as livestock waste decomposes, then 'scrub' it to create clean, renewable natural gas that is delivered to power plants. The process can reduce methane emissions by up to 70%, or an estimated 1,500 tons per year, on a 5,000-cow dairy farm.

By capturing methane that would otherwise contribute to global warming, we create a new source of domestic renewable energy."

Apr. 30, 2008 - BioEnergy Solutions