One of the world’s longest commercial trials of a seaweed supplement that the global meat industry hopes could slash methane from beef cattle has recorded much lower reductions in the potent greenhouse gas than previous studies.
Putting the supplement into the diets of 40 wagyu cattle in an Australian feedlot for 300 days cut the methane they produced by 28%.
The supplement was derived from the red seaweed species Asparagopsis, which has been widely promoted as being able to cut methane by more than 80%, with some experiments suggesting reductions as high as 96%.
Globally, the UN’s Food and Agriculture Organization estimates, methane from burping cattle – known as enteric emissions – releases about 2.1bn tonnes of CO2-equivalent a year, compared with the 37.5bn tonnes of CO2 from burning fossil fuels.
But because methane is about 80 times more potent than CO2 at warming the planet over a 20-year period, cutting methane is seen as a way to slow global heating faster.
The trial, reported by the red meat industry’s marketing and research group Meat and Livestock Australia (MLA), also found animals given the supplement ate less food and weighed 15kg less by the time they were sent for slaughter.
Dr Fran Cowley, a livestock scientist at the University of New England who led the trial, said it was the longest run so far using the red seaweed.
She said more research was needed to understand why the wagyu in the trial had not delivered the same level of emissions reductions as other experiments.
One factor could be the way the methane was measured in the trial, which used an open-air system in a feedlot compared with animals measured in dedicated indoor chambers.
But the trial report noted that other experiments over shorter timeframes using the same open-air measurement technique had recorded higher methane reductions.
“This was the biggest and longest trial so far and [the supplement] has not performed to the levels seen in the headlines people might have picked up. But that doesn’t mean it can’t,” Cowley said.
Cowley said she thought cuts of 90% “in the real world” were possible but there would also be economic factors that commercial producers would have to take, such as factoring in the cost of the supplement against the market benefits of methane reductions.
The seaweed was mixed in canola oil and added to the animals’ feed. In this trial it was given to the animals at slightly lower concentrations than other experiments that showed much higher methane reductions.
Cowley said it was also not clear why the animals on the supplement ate less food and put on weight more slowly.
Accounting for the extra 35 days the animals would have taken to reach the same weight would have theoretically meant the emissions savings were cut from 28% to 19% as they would have been alive for longer, all the time emitting methane.
Wagyu is considered a higher-end and more expensive beef. The trial found the seaweed supplement had no effect on the meat’s properties, including flavour.
Dr Rob Kinley is a pioneer of the Asparagopsis supplement and the chief scientist at FutureFeed – the Australian company that holds the intellectual property for its use globally as a livestock feed supplement.
He said it was not surprising the trial had seen lower results given the differences across breeds, measuring techniques, diets of the animals and the amount of supplement given to the animals.
But Kinley said it should be celebrated that the supplement was able to cut methane over such a long period and is confident other trials would deliver far higher reductions.
“The golden lining is even though it was just under 30% emissions reduction, it stayed that way for 275 days – it hardly faltered at all and I was impressed by that,” he said.
The Australian government funds a $29m research program to test different methane-reducing livestock supplements, including red seaweed.
The latest trial was financially backed by the country’s biggest beef producer, the Australian Agricultural Company (AACo), which helped run the trial and provided the animals.
The AACo chief executive, David Harris, said the company had anticipated bigger methane cuts but “reducing emissions by almost 30% is still significant”.
“There is no silver bullet to eliminating enteric methane emissions, but we’ll keep trying and we’ll discover how to make it work in our environment,” he said. “The important thing is that we are determined to get there.”
Most trials of methane-reducing supplements report emissions reductions only while animals are in the feedlot. Only 12%-15% of AACo’s emissions occur while the animals are in a feedlot.
An MLA spokesperson said: “Each time a new research project concludes, it places another piece into the puzzle, helping us understand the various products that might incorporate Asparagopsis and also helps us to understand further questions that need to be answered.”