On ecological and economical grounds alone, meat eating is now a looming problem for human kind ~World watch Institute – vision for a sustainable world 2016

pig farm

Feeding and growing animals for meat has inherent unavoidable inefficiencies. This is largely because the food the animals eat is not just converted to meat, it is also used to meet the animals’ high metabolic energy needs.  In addition, ruminant animals such as cattle and sheep produce methane as part of the digestion process, which is a very potent greenhouse gas, far more damaging than even carbon dioxide. These fundamentals are behind the reason why organizations such as the UN and the Worldwatch Institute have identified meat eating as one of the most important issues in addressing climate change1,2,3,4. Links to these reports are included in the reference section below.

To emphasize this issue, we recommend reading the results of the independent study by the Environmental Working Group (EWG), which investigated 20 popular meats and vegetable proteins for their life cycle greenhouse gas emissions. This detailed study from the USA looked at the full life cycle of the food, including all aspects of the production, transport, and storage, as well as the cooking and waste management processes. The data they used is from mostly peer reviewed or government sponsored studies in the USA and Europe. Read more on the study by the Environmental Working Group here.

Key findings of the EWG study5:
  • Greenhouse gas emissions from animal products are dramatically high in comparison to plant based food.
  • Lamb, beef, pork and farmed salmon were all particularly high. For example, per kg, lamb and beef consumption causes 40 and 30 times respectively more greenhouse gas emissions than the same quantity of lentils.
  • Meat was found to have other major environmental impacts in addition to greenhouse gas emissions.  These related to the high use of chemicals,  animal feed production, fuel use, pesticides use and water usage, as well as producing huge amounts of manure.
  • Slaughterhouses were found to generate vast amounts of toxic waste and high electricity use, much of this for pumping away the toxic pollutants.
  • Buying local was found to have a significant positive impact on the emissions footprint of vegetables but only a minor effect for meat. This is largely due to the fact that the emissions from meat production are so high that the proportion attributed to transport is a relatively small amount.
  • Significant emissions attributable to the processing of meat relate to freezing and packaging requirements. These vary from just 5% for lamb and beef, 12% for pork and 24% for chicken.
  • It is noted that while best management practices can reduce overall emissions and environmental harm from meat production, it was found that by far the most effective and efficient way to reduce greenhouse gas emissions and environmental impacts from livestock is to produce less meat.
  • Pasture fed beef was excluded in the study due to an inadequate amount of available data. This is discussed in more detail in the section on Australian Agriculture which shows how pasture feeding cannot meet the demand, and in any case may in fact be overall worse for the environment than grain feeding in factory farms.

Graph -life cycle greenhouse gas emissions of various foods.

emissionsAnother useful method to assess the relative inefficiencies of meat production is to look at the Feed Conversion Ratios (FCR).

The FCR is a measure of the amount of feed crops needed to produce a unit of meat. Not surprisingly the research in this area comes up with a wide variation in the numbers. This is due to the diversity of breeds, environments, and feeding practices. The numbers in the table below are for crop-fed farmed animals which, even in Australia represents the majority of meat produced. Note there are two figures, the first based on live weight and second on edible weight.  In America, 99% of meat comes from factory farmed animals whose feed must be obtained from purpose grown crops. These numbers show how much more food chickens, pigs and cattle consume than they produce in the form of meat.  Typical animal feed crops are corn, soy, and wheat. Grass fed meat, discussed separately, has different, but similar environmental concerns. The following summary data from multiple studies is presented on the web site for “A Well Fed World”.  Click here to review the details  and learn more about the significance of feed conversion ratios.

                              Feed Conversion Ratios (FCR) – Data from “A Well Fed World”

Note, the low end estimates for these FCRs  exclude waste.  It is noted that studies by those without a vested interest are more likely to publish the higher figures which are based on the actual food output, after removal of waste products. In any case, even the low numbers represent a very inefficient process. With pressure to improve their footprint the meat industries will try to improve their inefficiencies, but the improvements that can be made will always be limited by the inherent waste and inefficiency of growing crops to feed animals.

Other studies have been published using more comprehensive evaluation methods. These show that even the high-end of commonly cited FCRs are highly conservative. One example is the thesis6 that calculates the phytomass (plant biomass) energy that goes into animal production versus how much energy comes out in the form of animal sourced foods.  Such studies are more accurate and comprehensive as they include other factors, including waste and animals that are culled or die, among other things. Read the Chalmers University’s thesis on Turnover of Biomass in the Global Food System here.

Regardless of the precise numbers, producing crops (soy, corn, wheat, etc.) to feed animals is highly inefficient and far more resource-intensive than using crops for direct human consumption. This is highlighted by the following statistics:

  • 75% of all agricultural land is used for animal production.
  • More than a third of calories and half of the protein grown is inefficiently used as animal feed.

Learn more about the inefficiencies of producing crops to feed animals in the Worldwatch report here.

Additional Links & Resources

vegan resources

Livestocks Long Shadow – UN report

Report from the Worldwatch Institute – Livestock and Climate Change

A well fed world

Research paper from Chatham House, the Royal Institute of International Affairs – Livestock – Climate Change’s Forgotten Sector

Cowspiracy facts page

Facts on animal farming and the environment – One green planet

Report – Land use_ Agriculture and Forestry – Beyond Zero Emissions (BZE)

Research paper on a vegan agricultural system in Australia

Life cycle greenhouse emissions of food – Meateaters guide


[1] World Watch Institute. 2016. Is meat sustainable. [ONLINE] Available at:

[2] United Nations Environment Program. 2010. Assessing the environmental impacts of consumption and production. [ONLINE] Available at:

[3] World Watch Institute. 2009. Livestock and Climate Change. [ONLINE] Available at:

[4] Food and Agriculture Organisation of the United Nations. 2006. Livestock’s long shadow. [ONLINE]Available at:

[5] Environmental Working Group. 2011. Meat Eaters guide to climate change. [ONLINE] Available at:

[6] Wirsenius, S, 2000. Human Use of Land and Organic materials Modeling the Turnover of Biomass in the Global Food System. PhD. Göteborg, Sweden: Chalmers University of Technology and Göteborg University. [ONLINE] Available at: