Where are Cattle Emissions Currently At?05 November 2013
Manure management is at the heart of the solution to green house gas emissions, according to the World Food and Agriculture Organisation in its latest livestock emissions report.
An important emitter of greenhouse gases (GHG), the livestock sector also has a large potential to reduce its emissions.
This is the main conclusion drawn by the report “Tackling climate change through livestock”. This newly released report provides the most comprehensive global assessment made to-date of the livestock sector’s GHG emissions and its mitigation potential.
The report also presents a detailed assessment of the magnitude, the sources and pathways of emissions from different production systems and supply chains. Relying on life cycle assessment, statistical analysis and scenario building, it identifies concrete options to reduce emissions.
It comes at a time when the world needs to urgently reduce GHG emissions to avert catastrophic climate change. The livestock sector can make an important contribution to such international efforts by offsetting some of the sector’s emission increases, which are expected as demand for livestock products is projected to grow by 70 per cent by 2050.
GHG emissions from cattle represent about 65 per cent of the livestock sector emissions (4.6 gigatonnes CO2-eq), making cattle the largest contributor to total sector emissions. Beef production contributes 2.9 gigatonnes or 41 per cent of total sector emissions while emissions from milk production amount to 1.4 gigatonnes or 20 per cent of total sector emissions.11 Emissions allocated to other goods and services such as animal draught power and manure used as fuel represent 0.3 gigatonnes (Figure 10).
These goods and services supplied by livestock are particularly important in South Asia and sub-Saharan Africa, where they account for almost 25 per cent of emissions. Average emission intensities are 2.8 kg CO2-eq per kg of fat and protein corrected milk 12 for milk and 46.2 kg CO2-eq per kg of carcass weight for beef.
Main emission sources: enteric fermentation and feed fertilization
Enteric fermentation is the main source of emissions from cattle. Related emissions amount to 1.1 gigatonnes, representing 46 per cent and 43 per cent of the total emissions in dairy and beef supply chains, respectively (Figures 7, 8, 9 and 10). Feed emissions, including emissions from pasture management, form the second largest category of emissions, contributing about 36 per cent to milk and beef emissions.
Nitrous oxide emissions dominate, mostly originating from feed fertilization. When emissions from pasture expansion are added, feed emissions represent more than half of the emissions in specialized beef systems; dairy systems are generally not associated with pasture expansion.
Carbon dioxide emissions from energy use in feed supply chains represent about 10 per cent of overall emissions. Emissions from energy consumption on farms and in processing are negligible in beef and limited in dairy (about 8 per cent of emissions).
Higher emission intensity of the specialized beef herd There is a distinct difference in emission intensity between beef produced from dairy herds and from specialized beef herds: the emission intensity of beef from specialized beef herds is almost fourfold that produced from dairy herds (68 vs. 18 kg CO2-eq per kg of carcass weight) (Table 5).
This difference is primarily due to the fact that dairy herds produce both milk and meat while, on the other hand, specialized beef herds mostly produce beef. As a consequence, emissions from dairy herds are attributed to milk and meat while emissions from beef herds are allocated to meat (in both cases, a limited fraction is allocated to other goods and services, such as draught power, and manure used as fuel).
A closer look at emission structure shows that emissions from reproductive animals (the “breeding overhead”) exclusively explain the difference: when only fattening animals are considered, specialized beef and surplus dairy calves have similar emission intensity per kg of carcass weight. In addition, the breeding cohorts represent 69 per cent of the herd in specialized beef herds, compared with 52 per cent in dairy systems.
Because of differences in feed quality and herd management, grazing systems generally have higher emission intensities than mixed systems.13 Average emission intensities are particularly high for specialized beef raised in grazing systems in Latin America and the Caribbean, due to the landuse
change emissions related to pasture expansion.
The difference in emission intensities between grazing and mixed systems is less pronounced for beef from dairy herds and negligible for milk.
Emission intensities for beef are highest in South Asia, sub-Saharan Africa, Latin America and the Caribbean, and East and Southeast Asia (Figure 8). Higher emissions are largely caused by low feed digestibility (leading to higher enteric and manure emissions), poorer animal husbandry and lower slaughter weights (slow growth rates leading to more emissions per kg of meat produced) and higher age at slaughter (longer life leading to more emissions).
In Latin America and the Caribbean, one-third of the emissions (24 kg CO2-eq/kg carcass weight) from beef production is estimated to come from pasture expansion into forested areas. This estimate is to be taken with caution, given the numerous methodological and data uncertainties affecting land-use change emissions estimates (Chapter 2) (FAO, 2013a and 2013b).
In Europe, about 80 per cent of the beef is produced from dairy animals (surplus calves and culled cows), resulting in lower emission intensities, as explained above.
Generally, the emission intensity of milk production is lowest in industrialized regions of the world (below 1.7 kg CO2-eq/kg milk, compared with regional averages going as high as 9 kg CO2- eq/kg milk). Better animal feeding and nutrition reduce CH4 and manure emissions (lower release of N and volatile solids). Higher milk yields imply a shift of the cow’s metabolism in favour of milk and reproduction as opposed to body maintenance, contributing to lower emission intensities.
In low productivity regions, enteric fermentation is the main emission source. In industrialized
regions, feed production and processing, and manure together are as important a source of emissions as enteric fermentation.
Manure management emissions are relatively high in North America where, on average, 27 per cent
of manure from the dairy sector is managed in liquid systems that produce greater quantities of CH4 emissions.
Important GHG emissions
- The livestock sector plays an important role in climate change. It is estimated to emit 7.1 gigatonnes of carbon dioxide equivalent (CO2-eq) per annum, representing 14.5 per cent of all human-induced emissions.
- Beef and cattle milk production account for the majority of emissions, respectively contributing 41 and 19 per cent of the sector’s emissions. While pig meat and poultry meat and eggs contribute respectively 9 per cent and 8 per cent to the sector's emissions.
- The main sources of emissions are: feed production and processing (45 per cent of the total – with 9 per cent attributable to the expansion of pasture and feed crops into forests), enteric fermentation from ruminants (39 per cent), and manure decomposition (10 per cent). The remainder is attributable to the processing and transportation of animal products.
Sizeable reductions within reach
- Sector emissions could already be brought down significantly just through the wider use of existing best practices and technologies. Technologies and practices that contribute to reducing emissions already exist, but could be used more widely.
- A 30 per cent reduction of GHG emissions would be possible if producers in a given system, region and climatic zone adopted the technologies and practices currently used by their least emission intensive (emissions per unit of animal product) peers.
- Substantial emission reductions can be achieved across all species, systems and regions.
- Efficiency key to reducing emissions
- Possible interventions to reduce emissions are mainly based on technologies and practices that improve production efficiency at animal and herd levels. They include better feeding practices, animal husbandry and health management.
- Manure management practices that ensure the recovery and recycling of nutrients and energy contained in manure, and energy savings and recycling along supply chains, are further mitigation options.
Mitigation for development
- Most mitigation interventions can provide both environmental and economic co-benefits. Efficient practices and technologies can boost productivity and thus contribute to food security and poverty alleviation.
Urgent need for collective and global action
- Global action involving all sector stakeholders is urgently required to design and implement cost-effective and equitable mitigation strategies, and to set up the necessary supporting policies and institutional frameworks.
- The adoption of new practices and technologies will require a mix of supporting policies, incentives, research and on-the-ground extension work.
- This report is complemented by two technical reports providing a more in-depth analysis of emissions by sub-sectors (pig and chicken supply chains and ruminant supply chains).
You can view the full report by clicking here.
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