United Nations’ report analyses greenhouse gas emissions from livestock
The United Nations’ (UN) report measuring the livestock industry’s contribution to global warming says emissions can be reduced with practices already utilized by efficient operators.
The report, Tackling climate change through livestock: A global assessment of emissions and mitigation opportunities, claims that 14.5 percent of all human-caused greenhouse gas (GHG) emissions come from livestock supply chains, feed production, processing and manure decomposition.
According to the report, beef and milk production in cattle account for 41 and 20 percent of the sector’s emissions, respectively.
The emission intensity of beef from specialized beef herds – those that produce primarily beef – is almost fourfold higher than that produced from dairy herds.
Emission intensity from milk production is lowest in industrialized regions of the world.
“Emission intensities for beef are highest in South Asia, sub-Saharan Africa, Latin America and the Caribbean and East and Southeast Asia,” reports the UN. “Higher emissions are largely caused by low feed digestibility leading to higher intestinal fermentation and manure emissions, poorer animal husbandry, lower slaughter weights and higher age of slaughter that results in increased longevity leads to more emissions.”
“In the rumen, microbial fermentation breaks down carbohydrates into simple molecules that can be digested by the animal. Methane is a byproduct of this process,” it continues. “Poorly digestible, fibrous rations cause higher methane emission per unit of ingested energy. Non-ruminant species such as pigs can also produce methane, but the amounts are much lower by comparison.”
Emissions from small ruminants amount to 475 million tons of carbon dioxide.
At the same time, 299 million tons of carbon dioxide are attributed to meat production, 13 million tons of carbon dioxide to milk production and 46 millions tons of carbon dioxide to other goods and services.
“Small ruminants not only produce edible products but also important co-products including wool, cashmere and mohair,” the report continues. “Globally, 45 million tons of carbon dioxide are allocated to fiber production.”
Swine contributes nine percent of the sector’s emissions, and poultry comprises eight percent of emissions.
Feed production and processing and fermentation were identified as the two main sources of emissions.
Feed production and processing represented 45 percent of the sector’s emissions, while fermentation contributed 39 percent. Manure storage and processing represent 10 percent of emissions.
The UN states that emissions from the production, processing and transport of feed accounts for about 45 percent of sector emissions.
The fertilization of feed crops and deposition of manure on pastures generate substantial amounts of nitrous oxide emissions and represents a quarter of the sector’s overall emissions.
Ten percent of sector emissions were related to land-use change.
The study shows improvements in the industry can reduce GHG emissions by as much as 30 percent. The percentage can be reduced through technologies in feeding, manure and health management in addition to improving animal handling practices.
“Possible interventions include the use of better quality feed and feed balancing to lower intestinal and manure emissions,” the report states. “Improved breeding and animal health help to shrink the unproductive part of the herd and related emissions.”
“Manure management practices that ensure the recovery and recycling of nutrients and energy contained in manure and improvements in energy use efficiency along supply chains can further contribute to mitigation,” the report continues. “Sourcing low emission intensity inputs, feed and energy in particular, is a further option.”
The report states that manure contains two chemical components that can lead to GHG emissions during storage and processing: organic matter that can be converted into methane and nitrogen that leads to nitrous oxide emissions.
Methane is released from anaerobic decomposition of organic material, and nitrogen is released into the atmosphere as ammonia that can be later converted into nitrous oxide.
Shortening the duration of storage, ensuring aerobic conditions or capturing the biogas emitted in anaerobic conditions can control methane emissions from manure.
The organization claims that many of the recommendations for improving efficiency and reducing GHG emissions also boost production, providing people with more food and higher incomes that will benefit food security and poverty reduction.