Cows, seaweed and the race to lower farming methane emissions

A new study has found feeding seaweed to beef cattle can reduce methane emissions.
A new study has found feeding seaweed to beef cattle can reduce methane emissions. Photo credit: Getty

A "promising" new study out of the United States has found feeding seaweed to beef cattle can reduce methane emissions, without compromising meat quality.

But due to the large quantities needed for it to be effective, experts here say commercialising seaweed as a supplement for cows is not without its challenges.

The study, conducted by researchers at UC Davis University in California and recently published in the journal PLOS, monitored 21 Angus-Hereford beef bullocks over 21 weeks.

The animals were fed their normal diet of hay, grains and corn, while also given either zero, low or high concentrations of red seaweed  (Asparagopsis taxiformis).

The quantity of methane, hydrogen and carbon dioxide released by the individual animals was then measured over the testing period, with researchers finding a reduction in methane emissions of between 45 and 68 percent by those bullocks given the seaweed supplements.

The study's lead author Breanna Roque said though there was still more work to be done the results were very encouraging.

"We now have a clear answer to the question of whether seaweed supplements can sustainably reduce livestock methane emissions and its long-term effectiveness," she said.

According to the study, the proportion of forage in the base diet also had an influence on emissions, with the greatest reductions found in high seaweed-supplemented, low-forage diet, which reduced methane production by as much as 80 percent.

Meat from the animals was then subjected to professional grading and consumer tests, with neither the quality or flavour affected by the supplement.

"The taste panel considered all steaks, regardless of treatment group, to be moderately tender and juicy," the study said.

"This was consistent with the taste panel stating that they moderately liked the flavor of all steaks regardless of treatment group."

'You'd need to grow an enormous amount of it'

For Canterbury farmer Roger Beattie feeding seaweed to animals is nothing new. He's been harvesting kelp for around two decades.

He now harvests around 100 tonnes a year of giant kelp (Macrocystis pyrifera), mainly in Akaroa Harbour, and as well as using it for his own cattle also sells it to other farmers, particularly those using regenerative methods.

He's not driven by the goal of reducing methane emissions, but rather utilises it for its other beneficial properties, such as its high number of trace elements and high levels of potassium. Despite this he says he has no doubts "there are unidentified consequences that are a benefit".

However, he says despite the latest study showing promise for using red seaweed, he has concerns over how practical it would be and whether it could be easily commercialised.

"The problem is it's very, very lightweight and you'd need to grow an enormous amount of it," he told Newshub.

Those views were echoed by Dr Marie Magnusson, a seaweed biologist at the University of Waikato.

She said the results of the study were "very promising and exciting" but more work was needed before the industry can take off, particularly around issues such as safety, legislation and sustainability. 

The red seaweed analysed in the study is a warm-water species that in New Zealand only grows in the Kermadecs and is not currently harvested here. However, a cold-water variety of red seaweed -  Asparagopsis armata  - is found around both the North and South Islands and also shows similar methane reducing traits, with efforts already underway to develop it for commercialisation as a livestock feed supplement.

And while other species such as giant kelp - the type harvested by Beattie - most likely have similar methane reducing properties, studies have yet to conclusively show this, Dr Magnusson says, adding that in any case the levels would be much lower.

"Asparagopsis is currently by far the most effective seaweed species tested."

She says in other species much more seaweed would have to be added to cattle's feed on a daily basis to have a similar effect, "making it more challenging to produce enough biomass, and also increasing the likelihood there are undesirable effects on rumen fermentation processes."

She says if red seaweed (either Asparagopsis armata or taxiformis) is to be produced on a large scale it is unlikely to be through the harvesting of wild stock but would require controlled large-scale aquaculture.

"The amounts of seaweed required annually to treat, for example, a portion of the NZ dairy herd, or a portion of the US beef herd that go through feed-lots are too large to sustainably and reliably fill with ongoing harvesting of wild stock of seaweed," she told Newshub.

Despite the challenges, Dr Magnusson says due to overwhelming market demand, she believes it will be just a few years before the product is commercialised and farmers are feeding their cattle red seaweed in a bid to combat climate change.

"It's not that far away."