A vaccine is the best hope for limiting livestock methane emissions but a commercial product remains years away.
Years of research into reducing New Zealand’s agricultural greenhouse gas emissions have so far failed to produce a solution, although farming leaders insist there is cause for optimism.
The main targets are methane and nitrous oxide, which together account for about half New Zealand’s emissions. Methane is produced in the rumen of cattle, sheep, deer and goats, where microbes – methanogens – break down the animals’ food. In the process, they produce methane, most of which is belched into the atmosphere.
Most nitrous oxide comes from animal urine. The nitrogen released by a cow urinating on a paddock is more than the soil and plants can take up, and some of the surplus is converted into nitrous oxide and some is leached through the soil as nitrate. The wetter and more compacted the soil, the more nitrous oxide is produced.
Rick Pridmore, chairman of the Pastoral Greenhouse Gas Research Consortium, says researchers have found forages such as brassicas that reduce the amount of methane produced in the rumen, but the gains are likely to be offset by an increase in nitrous oxide emitted from the soil. That’s because farmers use break-feeding – using a moveable electric fence to ration grazing – which leads to pugging and compaction of soils that in turn increases nitrous-oxide emissions.
Some animals have been found to be genetically primed to produce lower methane, says Pridmore. The problem is that it could take 20 years to breed that trait through the whole population, and produce only a 5% reduction in methane. “That doesn’t mean we walk away from that, but we are working on the premise that we need solutions that work by 2030.”
Key areas of research are chemical inhibitors that could be administered in bolus form into the animal to counteract methane production, or a vaccine to tackle methanogens.
A German company has developed an inhibitor that it claims can reduce methane by 30%, and is aiming to have a product on the market by 2019. But it is geared towards livestock raised in feedlot systems typical of the Northern Hemisphere, and is not regarded as practical to administer to New Zealand’s pasture-grazing animals.
Pridmore says the consortium is also working on an inhibitor, and has identified five compounds that could work. But he says a commercial product that farmers could use is at least eight years away.
The most promising area of New Zealand research is on vaccine development but, again, a commercial product is at least seven years away. He says the aim is to knock back methane production by at least 20%, which researchers believe can be done without affecting animal productivity.
A vaccine would be developed from antibodies in the animals’ saliva and would generate an immune response to thwart the activity of the methanogens.
If a commercial vaccine can be developed, the global market could be enormous. Research by scientists here and overseas has shown all ruminants have the same kind of methanogens, regardless of diet or species. “That means when you find the solution for dairy cows and sheep, it is probably going to work on every ruminant in the world,” says Pridmore. “That’s why we are so wedded to trying to do this very difficult task. Everything I know about the vaccine gives me great positive feelings that they are going to nail the impossible.”
First published in the Listener on October 21