The U.S. government funded research into methane emissions from sheep digestive systems — flatulence and burps — to see why some sheep produce more of the greenhouse gas than others.
Researchers with the Energy Department’s Joint Genome Institute wanted to find out exactly why animals of the same species produce different levels of methane. The ultimate hope of the the research is to find ways to breed livestock that produce less methane when they pass gas.
“The deep sequencing study contributes to this breeding program by defining the microbial contribution to the methane trait, which can be used in addition to methane measurements to assist in animal selection,” said senior scientist Graeme Attwood with AgResearch Limited, a senior author on the paper.
JGI researchers looked at the methane emissions of 22 sheep that are part of a breeding program in New Zealand that aims to breed sheep that emit less methane. They found that sheep with low methane-emitting flatulence had elevated levels of Methanosphaera — a species of methanogen. Sheep with high methane-emitting flatulence had elevated levels of the methanogen Methanobrevibacter gottschalkii.
Researchers “then identified a methane-producing pathway and three variants of a gene encoding an important methane-forming reaction that were involved in elevated methane yields,” according to JGI.
“We wanted to understand why some sheep produce a lot and some produce little methane,” said JGI Director Eddy Rubin. “The study shows that it is purely the microbiota responsible for the difference.”
The publishing of the study comes as the Obama administration launches its plan to cut methane emission in its crusade against global warming. The largest man-made source of methane emissions comes from livestock, particularly cows and sheep.
Republicans have warned that regulating methane from livestock could lead to de facto taxes on animal flatulence. The Obama administration wants to reduce methane emissions from the dairy industry by 25 percent by 2020, which have lawmakers worried.
“The agriculture community is committed to environmental stewardship, which is evidenced by the 11 percent reduction in agriculture-related methane emissions since 1990,” Republicans, led by South Dakota Sen. John Thune, wrote to the Obama administration. “It is our hope that the EPA, USDA, and DOE will work with Congress and the agriculture industry to outline voluntary measures that can be taken to reduce emissions without imposing heavy-handed regulations on farms across America.”
The Environmental Protection Agency says that methane is 28 times more potent of a greenhouse gas than carbon dioxide and atmospheric levels of it have reached 1,800 parts per billion. One-fifth of methane emissions come from livestock, according to the EPA.
Cows and sheep are called “ruminants,” meaning they get their nutrients by fermenting it in one of their specially designed stomachs before they digest it. Bacteria within these animals’ “rumen” produce methane which is released when the animals belch or flatulate.
Scientists have long been looking into ways to reduce or capture methane emissions from animal flatulence for some time. In May, Argentinian government scientists announced they had developed a backpack for cows that traps methane and turns it into green energy.
“As cattle release greenhouse gases (GHGs) into the atmosphere, we propose a practical and economical way to sequester these emissions and energy use as a substitute,” said Guillermo Berra, INTA’s animal physiology coordinator.
Each backpack can be filled 1,200 liters of cow flatulence each day which is then taken to a lab, where they separate the methane emitted by the cow — about 250 to 300 liters per day. The methane is compressed and stored in containers which to power appliances and cars.
“A cow emits about 300 liters of methane per day, which can be used to operate a fridge capacity of 100 liters at a temperature of between two and six degrees for a full day,” Ricardo Bualo, an INTA technician involved with the project.
But technologies like this are costly and likely not practical for widespread adoption, which is why JGI researchers are looking into different ways farmers can breed lower emitting livestock.
“[T]here needs to be an incentive for farmers to incorporate low methane animals into their flocks, that is, achieving better performance with the low methane animals or being able to claim carbon credits,” said Attwood.
“If everything went well you could expect introduction of the low methane trait to begin in three years, and for there to be slow but incremental changes to the sheep industry in subsequent years,” he added.
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