Extract from ABC News
Feeding cattle a small amount of a seaweed species found in Australia has been shown to reduce their methane emissions by up to 86 per cent.
Key points:
- Red seaweed contains a compound that can reduce the production of methane
- Proponents say it could be the equivalent of removing 100 million cars from the road if adopted by the agriculture industry
- Some scientists warn the side effects of eating red seaweed on a large scale could include the production of ozone-depleting gas
Supplementing either 0.25 per cent or 0.5 per cent of a cow's daily feed with Asparagopsis taxiformis — a red seaweed native to Australian coastal waters — resulted in an average drop in methane production of over 50 per cent and 74 per cent respectively over a 147-day period, according to a study published today in the journal PLOS.
Methane is a potent greenhouse gas that has a warming potential around 25 times that of CO2 over a 100-year period.
Enteric methane emissions — emissions produced in the rumen of livestock — are responsible for as much as 14.5 per cent of the annual greenhouse gases produced by human activity.
The potential to cut emissions from cattle so dramatically could significantly reduce the impact the beef industry has on climate change, according to study lead author and animal science researcher Ermias Kebreab from the University of California.
"There needs to be a few more studies, but we see this as having a huge potential to reduce methane emissions," Professor Kebreab said.
"We would say this is a win-win scenario."
Primitive microbes called archaea use the carbon dioxide and hydrogen produced by digestion of food in a cow's gut to produce their own energy.
In doing so, they create methane as a by-product, which is mostly burped out the cow's mouth and not farted out, as is commonly thought.
So how does eating red seaweed work?
Asparagopsis taxiformis contains bromoform, which interrupts that process in its final stages and stops methane from being produced.
The result is a reduction in methane emissions that is unparalleled, said Rob Kinley of the CSIRO and chief scientist of Future Feed.
"It stands alone. There are none others even close to it. There are no other compounds of any type, whether they're seaweed or [synthetic] chemicals, that can take the methane down that far without hurting the animal," Dr Kinley said.
"Methane isn't necessary to the animal, it's just there as a by-product of evolution."
Future Feed, which is a partnership between the CSIRO, Meat and Livestock Australia (MLA) and James Cook University, is focusing on research and development of seaweed-based supplements for methane reduction for the cattle industry.
While the technology is mainly aimed at feedlot cattle, according to Future Feed's own estimates, the global impact on methane production could be significant.
"If 10 per cent of the livestock producers added 1 per cent of Asparagopsis seaweed meal to the daily feed intake of ruminant livestock, it is like removing 100 million cars off the road," their website states.
According to Dr Kinley, advances in their research means only between 0.2 per cent and 0.4 per cent of daily feed now needs to be supplemented with Asparagopsis.
How does it affect the quality of the meat?
For the study, 21 Angus-Hereford steers were randomly allocated to either a control group, a low-supplement or high-supplement group, with the low and high groups having 0.25 per cent and 0.5 per cent of their diet respectively supplemented with A. taxiformis.
Methane data was then collected every three weeks for 147 days.
The seaweed was collected by the CSIRO from Humpy Island in Keppel Bay, Queensland.
Although the methane-reducing properties of seaweed have been researched before, this is the longest field test of A. taxiformis, according to Professor Kebreab.
"We show that it works for at least 21 weeks of continuous use, " he said.
"There was some concern [about whether] the cows — really the microbes in their gut — could adapt to [the seaweed]."
But the study actually found the gut microbes became more efficient over time using the increased availability of hydrogen, according to Dr Kinley.
They also found that meat quality and taste were not affected in any way that was discernible by a tasting panel, and bromoform was not present in the meat at the detectable threshold of 0.06 milligrams per kilogram.
But there are some downsides
Sustainable agriculture expert Richard Eckard of the University of Melbourne said the results were promising, but more work was needed to establish whether or not the product would be safe to be used at scale.
"There are always the caveats: yes, it can reduce methane, but it's not an entirely natural product that cows eat, so what are the implications?" Professor Eckard said.
Bromoform is naturally released from the oceans via algae and phytoplankton, and is a source of ozone-depleting bromine when it enters the stratosphere and troposphere, although it is considered a short-lived ozone depleting substance.
It's currently used as a solvent, including in the extraction of minerals, and was also used as a fire retardant in the past.
Professor Eckard said that doesn't mean we shouldn't use it to reduce methane emissions; just that we need to be led by the science.
"We're not saying that these are problems, but before we produce another cane toad, we need to be really careful that we're not letting the sales machine get ahead of the science," he said.
"We want to know if we feed all the livestock in the world seaweed, what is the total bromine that reaches the ozone layer? That's what we want to know, and we don't know that.
"[But] I think it's brilliant, it's really taken us forward in our understanding of how much we can reduce emissions.
"Instead of potentially having to get rid of the livestock industry, we can reduce methane by 80 per cent."
Efforts to get the technology into the New Zealand agriculture industry, where 49 per cent of the country's greenhouse emissions come from agriculture, have been met with some resistance.
New Zealand's Agricultural Greenhouse Gas Research Centre deputy director Andy Reisinger has previously raised the issue of ozone depletion from the technology, and recently told the New Zealand press his concerns haven't been allayed.
"I don't think it's a bad idea, [but] I think it's an idea where claims have run ahead of the evidence and people haven't addressed the core problems," he said.
In response to questions about the potential impact to the ozone layer, a spokesperson for Future Feed said they had done an environmental risk assessment.
"All seaweed produces bromoform but Asparagopsis is unique in that it retains the bromoform, which is why it has such powerful anti-methanogenic properties. The bromoform is degraded in the rumen itself," the spokesperson said.
"The environmental benefits in methane reduction … should far outweigh the minimal environmental impact."
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