Higher quality pastures cutting emissions

A methane measuring collar in operation

At a glance

• Scientists have developed a method to measure methane emissions flock-wide.
• Moving sheep from lower quality ryegrass to lucerne reduced emissions from 37 to 27 grams per sheep per day.
• Strategic use of dietary oils can reduce cattle emissions by 20 per cent.

Moving stock on to higher quality pastures can reduce methane emissions by a third, according to a recent Victorian study.

Primary Industries Climate Challenges Centre (PICCC) acting director, Associate Professor Richard Eckard, who led the joint DPI and University of Melbourne project, said the findings had significant environmental benefits and could help farmers financially if an effective scheme to reward carbon offsets was introduced.

The study was part of the Department of Agriculture, Forestry and Fisheries (DAFF) Reducing Emissions from Livestock Production Program. The research focussed on how methane can be measured and how diet can be adjusted to reduce emissions in the more intensive, higher rainfall areas of Australia.

Scaling up

Typically, methane emissions from cattle have been measured on a single cow basis, for example by putting one cow in a methane chamber and measuring the inputs in and the emissions out, or through using a collar on each cow for measurement in the field.

The new study looked to develop a method to measure emissions on a larger scale and on different breeds, or types of animals such as beef cattle and sheep.

The beam from the FTIR can measure a range of gases, including methane, in its path. One of the first tasks of researchers from PICCC, prior to its official opening in February 2011, was to co-ordinate the deployment of two FTIRs — one for upwind, another for downwind.

Working first on the cattle at DPI Ellinbank, researchers were able to test the use of two FTIRs against data collected from collars put on the cattle.

"We got to the point of being fairly confident we had the method working," Professor Eckard said.

"We thought, let's take this and see if will work on smaller animals."

Off the sheep's back

Project leader Richard Eckard

Three trials were subsequently carried out at DPI Hamilton, together with the University of Wollongong, to see if the method could work on sheep, and later, what dietary adjustments could be made to reduce these emissions.

The first trial focussed on adjusting the method. When measuring cattle emissions the researchers had initially hung a paint ball canister filled with nitrous oxide around the cow's neck. When it came to the sheep, they found they had to use Velcro to secure the canister to the sheep's back.

Using the canister enabled the researchers to cross-check exactly how much nitrous oxide was released, with how much nitrous oxide gas was measured downwind. They used the same ratio to then calculate the amount of methane released using the methane detected by the FTIRs.

The second trial looked at the impact on methane emissions when sheep were moved on to different diets.

Professor Eckard said the results were convincing. "We're confident that as you move them from dead, stalky ryegrass to lucerne, the animals drop their emissions substantially," he said.

The figures showed that Merino sheep grazing on higher quality ryegrass emitted about 20 grams of methane per sheep per day, while Coopworths measured 28 grams of methane.

"As these were separate experiments, we cannot say these differences represent breed effects, but this does indicate that management systems will differ in methane," Professor Eckard said.

Moving the Coopworths on to low quality summer ryegrass increased emissions significantly, taking the figure per sheep per day up to 37 grams. When the Coopworths were put on lucerne, methane emissions dropped back to 27 grams.

"That's a third less methane per animal," Professor Eckard said. The third trial ended last November and the results are currently being analysed. The methane measurements are within the range expected for sheep and differences in diet are as expected, giving the team confidence that the method is working for cattle and sheep.

Dietary oils lower gas

The study adds to findings from another part of the same project looking at cattle emissions in methane chambers. This found adding dietary oils to cattle feed could reduce emissions significantly.

Professor Eckard said this project looked at using waste products from existing industries that had high oil contents such as brewer's grain, or bio-ethanol by-products. Taking those results and reviewing them against international studies of sheep, beef and dairy cattle, the study concluded that every one per cent of oil fed into a ruminant's diet translated to an emissions reduction of 3.5 per cent.

But he cautioned that this didn't work if the feed source was already high in oil. "In the spring period our ryegrass gets up to around 5 per cent oil anyway and you can't go above 7 per cent, so you don't have as much margin, but in the summer you might have pasture with only 1.5 per cent oil, so that gives you a bigger window to add oil."

In that scenario, adding 5.5 per cent oil could reduce emissions by 15–20 per cent. It would also increase milk production due to the slow-release energy provided by oil.

Trading gas for cash

Professor Eckard said as well as achieving production increases from feeding oils, added benefits to farmers were possible if a carbon offset program went ahead in the future.

"Right now the economics might be marginal, but an add-in incentive could make this a profitable thing to do," he said.

Professor Eckard gave the example of a flock of sheep that were traditionally fed on low quality rye grass being shifted to lucerne pastures. "That could be a reduction in methane by a third that could potentially be credited to you in carbon credits."

He said the system would be difficult to implement on an individual farm basis, so it's likely this would be through an aggregator such as a fertiliser or dairy company.

"Dairy companies have regular engagement with the farmer. They collect a lot of quality assurance information on milk quality and hygiene.

"It's very easy to build in on that data collection some of what the farmer is doing on-farm."