The global livestock sector emits almost 6,000 million metric tonnes of carbon dioxide equivalent (MtCO2e) per year at 2008 levels and accounts for about 11 percent of global greenhouse gas emissions. Emissions from the sector are expected to increase 70 percent by 2050.

PBL, 2009

Neil Palmer, CIAT

Extra facts

  • Roughly one-third of livestock emissions come from land use and land use changes.
  • Indirect emissions from the clearing of forests due to the encroachment of grazing into forested areas, as well as from the cultivation of feed crops play an important role in the total agricultural greenhouse gas emissions.
    • FAO (2006) calculates that globally, livestock-induced land use change generates 2,400 MtCO2e a year, or approximately 4 to 5 percent of global greenhouse gas emissions.
    • The PBL report (2009) gives a slightly different number, attributing about 2,200 MtCO2e per year to land use and livestock-induced land use change.
  • If CH4 (methane) emissions grow in direct proportion to increases in livestock numbers, then global livestock-related methane production is expected to increase by 60 percent by 2030. However, changes in feeding practices and manure management could lessen this increase (Smith et al., 2007: 504).
  • Emissions from livestock are highest per capita in high-income countries, with estimates ranging up to 31 percent of total emissions in the European Union. On the other hand, emissions may be higher per animal in low-income countries (Garnett 2009).
  • Animal protein from monogastric animals (largely pigs and poultry) is more efficient in terms of grams of protein per unit of greenhouse gas emissions than animal protein from ruminants (cattle, sheep and goats). However, this simplistic comparison does not take into account key issues such as the suitability of land for pasture or feed production, nutritional value beyond protein or the use of by-products (Garnett 2009).
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Methods, caveats and issues

Livestock emissions arise from the following sources (adapted from PBL, 2009: 170):

  • Ruminants (sheep, cattle, goats) release methane during the digestion of food.
  • Direct nitrous oxide (N2O) from livestock excreta (manure).
  • Indirect emissions from the production of feed crops, as the production and use of fertilizer on land leads to emissions of CO2 and N2O.
  • Deforestation and the conversion of grassland into arable land release significant amounts of CO2, methane (NH4) and nitrous oxide N2O from the soil.
  • The transport of feed, livestock and animal products also causes emissions, but they are relatively small compared to the other sources.

Methods and assumptions

PBL, 2009:

A key FAO report, Livestock's Long Shadow (FAO 2006), drew attention with its conclusion that (up to) 18 percent of global greenhouse gas emissions are associated with livestock. PBL sets the total at 6,000 MtCO2e per year, which adds up to 12 percent of the global GHG emissions. This is lower than the highest estimate in the FAO report (FAO 2006)—7.1 gigatonnes per year. One reason for this difference is that PBL (2009) use the most recent IPCC Guidelines (from 2006) for calculating nitrous oxide emissions, while the FAO use the previous version of the IPCC Guidelines. A second reason why the FAO gives a higher percentage (18 percent) is that FAO assumes a much lower total global emissions, i.e. 40 versus 48.9 GtCO2e (gigatonne carbon dioxide equivalent) per year (PBL, 2009: 170). However, as both PBL (2009) and FAO (2006) point out, the magnitude of the emissions caused by livestock is very difficult to quantify.

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Sources

  • [PBL] Planbureau voor de Leefomgeving. 2009. Milieubalans 2009. Bilthoven: Planbureau voor de Leefomgeving. (Available from http://www.pbl.nl/nl/publicaties/2009/milieubalans/)
  • Smith P, D Martino Z, Cai D, Gwary H, Janzen P et al. 2007. Agriculture. In: Metz B, Davidson OR, Bosch PR, Dave R, Meyer LA, eds. Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press.
  • Stehfest E, Bouwman AF, van Vuuren DP, den Elzen MGJ, Eickhout B et al. 2008. Vleesconsumptie en klimaatbeleid. Publicatienummer 500110004. Bilthoven: Planbureau voor de Leefomgeving.
  • Garnett T. 2009. Livestock-related greenhouse gas emissions: impacts and options for policy makers. Environmental Science & Policy 12:491-503.
  • [FAO] Food and Agriculture Organization of the United Nations. 2006. Livestock’s Long Shadow. Rome: FAO. (Available from http://www.fao.org/docrep/010/a0701e/a0701e00.HTM)
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