Livestock behind 7.1 gigatonnes of GHGs

Photo: Flickr.com/Paul Stevenson/CC BY

There is potential to decrease greenhouse gases from the livestock sector by as much as 30 per cent by just improving methods and techniques – this is the conclusion of a recent report from the FAO.

The livestock sector causes greenhouse gas emissions corresponding to 7.1 gigatonnes of CO₂-equivalents each year. That is 14.5 per cent of the total human-induced global greenhouse gas emissions, according to the report “Tackling climate change through livestock”, published by the Food and Agriculture Organization of the United Nations (FAO) in August. This can be compared to the often-cited figure of 18 per cent from their previous report “Livestock’s long shadow” from 2006. The model behind it has since been adjusted, resulting in lower estimates for the contribution from land use change, while the impact from methane is assessed as being higher than before. However it all adds up to a heating potential quite similar to the old model. The 3.5 per cent decrease in the relative contribution from livestock is explained by the fact that overall global emissions have increased over the past seven years.

Cattle production is by far the largest emitter, with dairy and beef respectively accounting for 41 per cent and 22 per cent of the sector’s emissions (figure 1). Beef is also the product with the highest intensity of emissions (figure 2). One reason why cattle production scores so highly is that ruminants (which also include sheep and goats, but in smaller numbers) produce methane during the natural process of enteric fermentation. This methane constitutes 39 per cent of the sector’s total contribution to global warming (figure 3). Another reason is that cattle production requires more feed than other forms of livestock production. Since cattle only produce one offspring each year there will be a larger overhead for the parent generation (which also needs to eat), compared to pigs and chickens. Emissions from all livestock feed production represent 45 per cent of the total sector’s emissions. This includes carbon dioxide emissions from land use change, fertilizer production and transport, as well as nitrous oxide emissions from fertilizers and manure applied to arable land.

Figure 1 Global estimates of emissions by species (includes emissions attributed to edible products and to other goods and services, such as draught power and wool).

Figure 2 Global emission intensities by commodity.

Figure 3 Greenhouse gas emissions from global livestock supply chains, by production activities and products.

Turning to geographical differences, emissions are highest (tonnes of CO₂-equivalents per land area) in some regions with intensive livestock production in Europe, India and China. However the highest emission intensities (CO₂-equivalents per kilogram of edible protein) are found in extensive systems in Africa and Latin America. The production system with the highest overall emissions is beef cattle farming in Latin America, with more than a tenth of all global emissions.

There are also variations within production systems in specific regions. This fact is taken into account in the study by modelling the potential reduction of emissions if all farms in the region were to adopt the practices and the technology of the farms with the lowest emission intensities, while keeping production outputs constant. In the report this is called “to close the emission intensity gap”. If this was done globally and all farms adopted the standard of the best twenty-five per cent within their region and system, emissions could be reduced by 18 per cent (1.1 gigatonnes) and if all farms adopted the management and technology of the best ten per cent, emissions could decrease by 30 per cent (1.8 gigatonnes).

The authors note that this estimate may be conservative, since it does not take into account all readily available abatement techniques, some of which are currently used only by a fraction of all farmers.  But one could also argue that it is optimistic since it is based on the assumption that all the barriers that prevent the lowest performing farms from applying the practices of the best can actually be removed.

As a complement to this rather raw statistical exercise, the FAO also made five case studies of regional livestock systems and estimated the scope for improvements within each system. The highest potential from an emission intensity point of view among those studied was West African sheep and goat production, where emissions per kilo of edible protein could be reduced by 27 to 41 per cent through higher feed quality, preventive health measures, improved breeding and better grazing management.

The system with the highest potential in absolute numbers was Latin American beef production. Here it would be possible to reduce emissions by between 190 and 310 million tonnes of CO₂-equivalents by improving animal health and husbandry, grazing management and forage quality.

Dairy production in OECD countries was the only element of the systems scrutinised that is based in developed countries. These systems are already highly efficient when it comes to kilogram of product per animal unit, which also means rather low greenhouse gas emissions per kilogram of product. However three areas for intervention were identified. The first is the use of dietary fat supplements made from linseed oil or cottonseed oil, which limit the production of methane from enteric fermentation. Another mitigation area applies to farms that use liquid manure treatment. A wider adoption of techniques for anaerobic treatment and production of biogas could reduce methane emissions as well as replacing fossil fuels. The third option is to adopt energy-efficient technology and use low-carbon energy sources. These measures could together reduce emissions by 25–28 per cent in North America and 11–14 per cent in western Europe. The difference is mainly due to the fact that liquid manure systems are more common in North America, which therefore has greater scope for improvement.

It should be noted that there are two deliberate but important limitations in the scope of the report:

• There is a high risk of various rebound effects. Increased efficiency might induce increased production, due to more opportunities to increase animal density, lower prices of products that stimulates demand or higher revenues that permit investment in expansion. This risk is to some extent considered and the authors suggest that it could be addressed by setting a ceiling for total emissions through tradable or non-tradable emission permits.
• Secondly the report only considers measures in the area of production. Another important area for intervention is to limit demand for animal products. Even if the sector managed to close the 30 per cent emission intensity gap, emission reductions would be offset by an increase in production induced by growing demand in the coming decades (figure 4).

Figure 4 Interactions between trends in livestock production, GHG emissions and mitigation efforts.

But the need for demand-side measures does not exclude production measures. One interesting aspect is that most greenhouse gas emissions from the sector can be linked to losses in nutrition, energy or soil organic matter. Or in other words there are potential wins in other areas for farmers to be made along with greenhouse gas mitigation. If nitrous oxide emissions from the soil are reduced, more nitrogen will stay within the system and less money will be spent on fertilizers. More energy-efficient production will reduce costs for electricity and heating. Sequestration of carbon or less decomposition of carbon will improve the quality of the soil.

But of course there are often issues such as finances or lack of knowledge that prevent farmers from picking these win-win fruits of greenhouse gas mitigation. The last chapter deals with how policy could be designed to facilitate the dissemination of low-carbon practices.

• This could include providing infrastructure for knowledge transfer such as demonstration farms, field schools, farmer networks or sector round-tables.
• Support for research and development.
• Financial instruments, such as low-interest loans or micro-financing for investments.

There are also some pitfalls that policy makers must watch out for. For small farmers in developing countries, animals are not only kept simply for production reasons. Some animals are kept for risk-mitigation, financial services, draught power and the provision of manure from crops. With a pure production perspective some of these services could be lost.

Carbon sequestration is another area of concern. The FAO estimates that improved grassland management has a global potential to sequester 409 million tonnes of CO₂-equivalents per year (6 per cent of all agricultural emissions). The main limitation of carbon sequestration as a measure is that it is extremely difficult to guarantee its permanence. Researchers have observed large losses of soil carbon in Europe during droughts. Additionally, the report notes that most grasslands probably reach a saturation level with time and that the potential then subsides.

Kajsa Lindqvist

Report: Tackling climate change through livestock.