How Much Does Animal Agriculture Contribute to US Greenhouse Gas Emissions?

ANALYSIS - As the November 2015 Global Climate Change Conference COP21 concluded in Paris, 196 countries reached agreement on the reduction of fossil fuel use and emissions in the production and consumption of energy, even to the extent of potentially phasing out fossil fuels out entirely, writes Frank Mitloehner.
calendar icon 8 June 2016
clock icon 7 minute read

Both globally and in the US, energy production and use, as well as the transportation sectors, are the largest anthropogenic contributors of greenhouse gasses (GHG), which are believed to drive climate change.

While there is scientific consensus regarding the relative importance of fossil fuel use, anti animal-agriculture advocates portray the idea that livestock is to blame for a lion’s share of the contributions to total GHG emissions.

Divorcing political fiction from scientific facts

One argument often made is that US livestock GHG emissions from cows, pigs, sheep and chickens are comparable to all transportation sectors from sources such as cars, trucks, planes, trains, etc.

The argument suggests the solution of limiting meat consumption, starting with “Meatless Mondays,” to show a significant impact on total emissions.

When divorcing political fiction from scientific facts around the quantification of GHG from all sectors of society, one finds a different picture.

Leading scientists throughout the US, as well as the US Environmental Protection Agency have quantified the impacts of animal production in the US, which accounts for 4.2 per cent of all GHG emissions, very far from the 18-51 per cent range that advocates often cite.

Comparing the 4.2 per cent GHG contribution from livestock to the 27 per cent from the transportation sector, or 31 per cent from the energy sector in the US brings all contributions to GHG into perspective.

Rightfully so, the attention at COP21 was focused on the combined sectors consuming fossil fuels, as they contribute more than half of all GHG in the US.

GHG breakdown by animal species

Greenhouse gas emissions by sector

Breaking down the 4.2 per cent EPA figure for livestock by animal species, shows the following contributors: beef cattle, 2.2 per cent; dairy cattle, 1.37 per cent; swine, 0.47 per cent; poultry, 0.08 per cent; sheep, 0.03 per cent; goats, 0.01 per cent and other (horses, etc.) 0.04 per cent.

It is sometimes difficult to put these percentages in perspective, however. If all US Americans practised Meatless Mondays, we would reduce the US national GHG emissions by 0.6 per cent.

A beefless Monday per week would cut total emissions by 0.3 per cent annually. One certainly cannot neglect emissions from the livestock sector but to compare them to the main emission sources would put us on a wrong path to solutions, namely to significantly reduce our anthropogenic carbon footprint to reduce climate change.

US Population Replace Incandescent with Energy Star bulbs = 1.2 per cent GHG savings

US Population “Meatless Monday” = 0.6 per cent GHG savings

In spite of the relatively low contributions to total GHG emissions, the US livestock sector has shown considerable progress during the last six-plus decades and commitment into the future, to continually reduce its environmental footprint while providing food security at home and abroad.

These environmental advances have been the result of continued research and advances in animal genetics, precision nutrition, as well as animal care and health.

US dairy and beef production carbon footprint reduced

Since the 1950s, the carbon footprint of the US beef and dairy sector has shrunk as production increased or stayed the same.


  • 1950: 22 million dairy cows produced 117 million tons milk
  • 2015: 9 million dairy cows produced 209 million tons of milk. (Fifty-nine per cent fewer cows produced 79 per cent more milk than they did in 1950.)


  • 1970: 140 million head of cattle produced 24 million tons of beef
  • 2015: 90 million (36 per cent fewer) head of cattle produce 24 million tons of beef

Globally, the US is the country with the relatively lowest carbon footprint per unit of livestock product produced (i.e. meat, milk, or eggs). The reason for this achievement largely lies in the production efficiencies of these commodities. Fewer animals are needed to produce a given quantity of animal protein food, as the following milk production example demonstrates:

  • The average dairy cow in the US produces 22,248 lbs. milk/cow/year. In comparison, the average dairy cow in Mexico produces 10,500 lbs. milk/cow/year, so it requires more than two cows in Mexico to produce the same amount of milk as one cow in the US.
  • India’s average milk production per cow is 2,500 lbs. milk/cow/year, increasing the methane and manure production by a factor of nine times compared to the US cow. As a result, the GHG production for that same amount of milk is much lower for the US versus the Mexican or Indian cow.

Production efficiency is a critical factor in sustainable animal protein production and it varies drastically by region.

Improvements in livestock production efficiencies are directly related to reductions of the environmental impact. Production efficiencies and GHG emissions are inversely related — when the one rises, the other falls.

The 2050 challenge to feeding the globe is real. Throughout our lifetime, the global human population will have tripled from three to more than nine billion people without concurrent increases of natural resources to produce more food.

Our natural resources of land, water and minerals (fertiliser) necessary for agricultural production have not grown but in fact decreased. As a result, agriculture will have to become much more efficient worldwide and engage in an efficient path similar to the one it has travelled down in US livestock production in recent decades.

UN’s FAO committee develops global benchmarking method

How can emissions accurately and fairly be assessed to lay ground for a path for solutions?

In its quest to identify a sustainable, scientific path toward fulfilling the future global food demand, the Food and Agriculture Organization of the United Nations (FAO) has formed an international partnership project to develop and adopt a “gold standard” life cycle assessment (LCA) methodology for each livestock specie and the feed sector.

The ‘Livestock Environmental Assessment and Performance Partnership’ (LEAP), engaged with more than 300 scientists from the world’s most prestigious academic institutions in this unprecedented effort to develop a global benchmarking methodology.

The first three-year phase project was finalised in December 2015 with six publically available LCA guidelines.

This globally harmonised quantification methodology will not only allow the accurate measurement by livestock species and production regions across the globe today, but will also identify opportunities for improvement and the ability to measure that progress in each region going forward.

Efficiency and intensification key to low-carbon livestock sector

Addressing the 2050 challenge of supplying food to a drastically growing human population can sustainably be achieved through intensification of livestock production.

Indeed, intensification provides large opportunities for climate change mitigation and can reduce associated land use changes such as deforestation. Production efficiencies reduce environmental pollution per unit of product.

The US livestock, poultry and feed industries are one of the most efficient and lowest environmental impact systems in the world. The research, technologies and best practices that have been developed and implemented over time in the US can also be shared with other production regions around the world.

It is important to understand that all regions have unique demands and abilities, and so require regional solutions. However, the advances in the US agriculture and food system can be adapted within these regional solutions. These significant environmental advances and benefits are in addition to the well-documented human health and developmental value of incorporating animal protein in the diets of the growing population.

The livestock sector is committed to continuous improvement of their environmental impact in North America, and to doing its part in transferring knowledge, technologies and best practices to enhance global environmental livestock impact by region.

Now is the time to end the rhetoric and separate facts from fiction around the numerous sectors that contribute emissions and to identify solutions for the global food supply that allow us to reduce our impact on the planet and its resources.

Frank Mitloehner is a professor of Animal Science and Air Quality Specialist at UC Davis. He recently concluded chairing a Food and Agriculture Organization of the United Nations committee to measure and assess the environmental impact of the livestock industry.

Sarah Mikesell


Sarah Mikesell grew up on a five-generation family farming operation in Ohio, USA, where her family still farms. She feels extraordinarily lucky to get to do what she loves - write about livestock and crop agriculture. You can find her on Twitter or LinkedIn.

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