Ireland’s emissions of greenhouse gas from agriculture are among the highest in the world, relatively speaking, but scientists here say that technological solutions are emerging that can provide significant cuts in such gases without resorting to drastic culling of herd numbers.
Agriculture and land use in Ireland produces 37.1 per cent of the country’s greenhouse gas emissions; higher than the global average, which hovers at about 25 per cent. Ireland is comparable to countries like New Zealand, which also has a high livestock to human population ratio.
Most emissions from global agriculture – about 60 per cent – arise from digestion inside the stomachs of cattle and sheep. It is there that microbes slowly break down the grasses and other foods consumed by ruminant animals, which produces the greenhouse gas, methane.
Scientists have strategies to reduce “enteric” animal methane emissions produced through the digestive action of microbes breaking down plant material inside the ruminant stomach.
“Technology can help tackle these problems, but it’s not an easy fix,” says Tommy Boland, professor of ruminant nutrition at the UCD School of Agriculture and Food Science. “The solutions include, breeding, feed management, feed additives, vaccination, animal health, sward type and fertiliser management,” he says.
A sward, in agriculture, is used to refer to the upper layer of soil, covered in grass, which the grazing animals feed upon.
It would seem on the face of to be a simple equation: the more animals grazing, the more methane gas gets produced. However, emerging technologies mean scientists have several ways to reduce such animal emissions, without the need for big reductions in herd.
At the top of the list, is old-fashioned breeding techniques, which have been used for centuries to select desirable traits in livestock animals. Over time, dairy cows have been bred to produce more milk, cattle to produce better beef and chickens to produce larger eggs.
It is possible now to breed livestock to produce less methane gas, as there can be a wide variation in emissions between individual animals with similar performance. The clear economic desirability of animals producing lower emissions led this trait to be included in the Economic Breeding Index (EBI), introduced in Ireland in 2001.
The purpose of the EBI was to identify dairy animals of superior genetic merit for profitability. The original five EBI traits were milk, fat and protein yield, survival, and the calving interval. The inclusion of low emissions means that, over time, the herd will reduce its methane gas emissions, even if numbers stay static.
The great advantage with breeding is that it is a long-proven method of bringing improvements in any animal trait of interest. Scientists estimate that the adoption of improved genetic breeding over the past 20 years has led to a reduction in the carbon footprint of dairy products in Ireland by 14 per cent, while further improvements are viable.
Dr Sinéad McPartland, a research officer at the Teagasc Animal and Grassland Research and Innovation Centre at Moorepark, has been capturing information about the emissions dairy cows are producing by piggybacking on existing national milk reporting networks. These measure how much fat and protein individual animals are producing and can also be used to measure their methane emissions.
“We have an idea there are good emitters and bad emitters, or animals emitting more than each other to produce, say the same amount of meat,” says McPartland. “By being able to capture this information and getting it on the national herd, is really important for us so we can select from the good [emitters] going forward.”
There is room for reducing emissions in sheep, too, given that scientists in New Zealand, have produced sheep that emit 10 per cent less methane. The situation with beef also looks promising with Professor Paul Smith of Teagasc conducting research showing a 30 per cent variation in methane emissions across beef animals with similar performance.
The methane produced by burping animals can also be reduced by addition of certain dietary ingredients or additives. There are many different additives being researched, the most promising of which are seaweeds, linseed oil and Bovaer, a commercial feed product developed for ruminants.
Such additives work best where animals are kept inside for most of the year, as this provides an opportunity to tightly control their diet. In Ireland, where animals are mostly outside grazing on the pasture, other, more relevant solutions are being worked on.
“Work in UCD and Teagasc clearly shows that improving the quality of grass fed to dairy cows and beef cattle will reduce methane emissions per kilogramme of meat or milk produced, and per day,” says Boland. “There is a lot of evidence to show that including white clover in the sward will reduce emissions from ruminant agriculture.”
This leads to the reduction in emissions of nitrous oxide, another greenhouse gas, says Boland, because less fertiliser is required.
“More recent work is looking at the use of multispecies swards, and again there is significant emissions savings through the reduction in fertiliser inputs,” says Boland. Such multispecies swards are also associated, says Boland, with better animal health and performance.
Gary Lanigan, a research officer with Teagasc, is looking at the merits of a range of scientific strategies to reduce emissions from agriculture. “We’ve been looking at adding in chemical amendments into slurry,” says Lanigan. “Acidifying the slurry reduces methane emissions successfully, actually, we see about a 90 per cent reduction.”
Research studies have also shown, says Lanigan, that a chemical called 3-NOP (3-nitrooxypropanol) has great potential to reduce emissions of methane from dairy cows. The chemical works by disrupting an enzyme in the rumen needed to produce methane. The emissions are thus stopped at source, inside the animal’s stomach.
Another line of attack, says Lanigan, is through use of low-emission fertilisers, like protected urea. Most farmers use calcium ammonium nitrate fertilisers that produce high emissions, he says, but the emissions from protected urea are three to four times lower.
Research is under way, led by New Zealand scientists, into developing a vaccine that would reduce methane output in ruminant animals. The goal is for the vaccine to trigger the animal’s immune system into generating antibodies in saliva that suppress the growth, and normal function of methane-producing microbes, methanogens, in the rumen.
This work is promising, but Dr Harry Clark at the New Zealand Agricultural Greenhouse Gas Research Centre estimates that it will be at least 10 years before a methane vaccine can be developed.
Ireland produces about 23 million tonnes of greenhouse gases from agriculture each year. This must be cut to between 16 and 18 million tonnes, scientists say, if the agricultural emissions targets set out in the national Climate Action Plan are to be achieved by 2031.
“Achieving the sectoral target of an emissions reduction of between five to seven million tonnes will be extremely challenging for agriculture,” says Laurence Shalloo, a research officer based at the Teagasc Animal and Grassland Innovation Centre at Moorepark in Fermoy.
“There are solutions currently available and more technologies that have shown significant promise – and will be available in the short term – that could get agriculture achieve over 15 per cent of a reduction in emissions.”