Beef Cattle and Greenhouse Gas Production
A new United Nations Report Reduces Bovine Contribution by 22%.
What Are Greenhouse Gases?
Solar radiation provides most of the heat energy which warms the Earth. Some incoming radiation is reflected by the atmosphere, a small amount is absorbed directly by the atmosphere, and rest strikes the Earth's surface. Part of this incoming radiation is absorbed by the Earth and then re-emitted back into the atmosphere in a form which can be absorbed by atmospheric gases such as water vapour, carbon dioxide and methane. These gases in turn release the energy back into the atmosphere, helping to warm the planet. The gases involved in this are called the "Greenhouse Gases" (GHG). While the Greenhouse Effect is a natural phenomenon, human activity has increased the levels of some GHG well above historic levels, causing a significant warming trend on a global basis.
The 2006 FAO Report
In 2006, the Food and Agricultural Organization (FAO) of the United Nations released a report on the role of animal agriculture in greenhouse gas (GHG) production, called "Livestock's Long Shadow"1. The FAO report concluded that livestock were responsible for 18% of all human related GHG production. This conclusion generated a lot of bad press for livestock, and especially the beef cattle sector. However, when independent scientists reviewed the report, many took issue with both the methodology employed and the conclusions. For example, Dr. Frank Mitloenher of the University of California (Davis) stated that when only the GHGs directly contributed by cattle and pigs in the U.S. were considered, livestock account for only about 3% of all greenhouse emissions. So it's important to look behind the executive summaries of these reports to fully understand their implications.
How were these very different conclusions drawn from the same data? In reaching their conclusion regarding livestock, the FAO had included a number of GHG sources which were not directly related to the animals, such as the conversion of forested land in South America to agricultural production, the processing of meat, and the transportation of product to consumers. While all of these are important sources of GHGs, we need to be careful we understand how they are being allocated. For example, as the human population continues to expand, land will continue to be converted from forest to food production, whether for crops fed directly to humans or though livestock first. And production systems vary dramatically depending on what region of the world you are looking at. So we also need to consider the results from a North American production system standpoint, in order to understand their relevance to our conditions.
The 2013 FAO Report
The FAO has published a new report on livestock's contribution to GHGs, titled "Tackling Climate Change Through Livestock"2 . This report continues their methodology of attributing a wide array of GHG emissions to livestock production. In this report, livestock's contribution to the total of human source GHGs is 14.5%, which is a reduction of about 20% reduction from the 2006 report. While this is welcome news, we still need to take a more in-depth look at the data understand where this conclusion comes from and how it applies to us.
Cattle are an important component of total livestock GHG production, due primarily to the amount of methane produced by microbial activity in the rumen. The FAO model estimates that on a world-wide basis, beef cattle account for 41% of total livestock emissions, with dairy cattle at 20%.
Beef Cattle Sources of GHG
The primary GHGs associated with cattle are methane, carbon dioxide and nitrous oxide. The relative contribution of various aspects of beef production on a worldwide basis is shown in Table 1. The major source of emissions is the rumen, from methane produced by microbial activity, followed by emissions from manure. The conversion of forest to pasture land is relevant only to Latin America and is occurring primarily in Brazil. It's important to note that the land conversion component of the FAO model is quite weak, with the 95% confidence interval for the effect being plus or minus 50%.
Table 1. Sources of Beef Cattle GHG Emissions (FAO 2013)
Regional and Production System Differences
The FAO report looked at the differences in GHG emissions from both different production systems and different world regions. Since the type of system used is determined in part by the climate, the regions and systems tend to be interrelated. The comparison was based on the intensity of emissions, which was measured as the kg of CO2 equivalent produced per kg of carcass weight. A selection of results by region is presented in Table 2.
There is a wide variation among regions for emission intensity. For example, beef production in Latin America produces 72 kg of CO2-eq per kg of carcass weight, while the rate in North America is less than 40% of this. Some of this difference is due to animal production efficiencies - for example, systems where cows are weaning a calf every year produce less GHG per unit of output than those producing one calf every 3 years. Another part of the difference is due to degree to which grasslands are part of production. In general, more extensive systems were found to produce more GHG per unit of output than intensive systems. However, this is another weak area in the FAO model, as scientists do not agree on the baseline impact of grassland production on GHG emissions, so it was omitted from the calculations. This is an important issue, as grasslands are considered by some to act as a "sink" (absorbs and stores) for CO2.
Table 2. GHG Emission Intensity for Beef Production by Region (FAO 2013)
*Carbon dioxide equivalent
Opportunities for Reducing GHG in Beef Production
The FAO report found that even within a region and production system, there is wide variation in the intensity of emissions - so a lot of improvement can be made within systems rather than by changing systems. In fact, the variation within a production system was almost as great as that among systems. There was an approximately 4-fold difference in emission intensity between the top 10% of producers and the bottom 10% of producers within a system.
The report used this information to predict that if all producers within a specific location/system adopted the best practises of the top 25%, GHG intensity could be reduced by 18%. And if all adopted the practices of the top 10%, GHG intensity could be reduced by 30%.
In the next issue of Virtual Beef we will look at how the Ontario beef industry can reduce GHG emission intensity.
1 FAO. 2006. Livestock's long shadow - Environmental issues and options, by H. Steinfeld, P. J. Gerber, T. Wassenaar, V. Castel, M. Rosales & C. de Haan. Food and Agriculture Organization of the United Nations (FAO), Rome.
2 FAO 2013. Gerber, P.J., Steinfeld, H., Henderson, B., Mottet, A., Opio, C., Dijkman, J., Falcucci, A. & Tempio, G. Tackling climate change through livestock - A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO), Rome.
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