Deakin University researchers have found a mix of algae scooped out a Victorian waterway and species of amphibious grass from a stream reduces methane production by up to 24 per cent.
The research proves that there are freshwater alternatives to methane-busting red seaweed, Aparagopsis taxiformis.
Aquatic ecologist Professor Rebecca Lester said the project was prompted by a landholder who asked about ways to limit their on-farm emissions having heard about the success of Asparagopsis taxiformis, which can reduce methane emissions in cattle by more than 90 per cent.
"Asparagopsis is amazingly effective and has a lot of potential," Prof Lester said.
"But it also has challenges, such as the issues surrounding growing something offshore in really high energy coastlines like ours, the amount you need to grow to make it a viable and scalable source of feed for livestock, and its susceptibility to disease.
"The other major challenge is its efficacy degrades through time.
"If you don't get it into cattle within some number of months, the impact that it has declines because the active ingredient is not a stable one in the long term."
Professor Lester and a team that included chemists, biochemists, and animal nutrition experts, assisted by the expertise in measuring methane emissions at University of Western Australia, set about finding if there were freshwater alternatives, and started by collecting samples from waterways in Victoria's Barwon River catchment.
Professor Lester said they were looking for species that were already widespread, native and not likely to be toxic or become environmental weeds.
The team collected two different samples, a natural mix of algae and the amphibious grass Montia australasica.
When fermented by rumen microbes in vitro, testing showed the algal mix reduced methane production by 24 per cent at a 20 per cent dose, and Montia australasica reduced methane production by 21 per cent, at a 50 per cent dose.
"This opens the door to saying well maybe we can optimise how we grow them," Prof Lester said.
"We just collected that little Montia plant from the side of a stream. If you grew it under particular conditions, then you might have a much bigger impact."
"We now have multiple species that have potential to be used as a feed additive to reduce methane production in livestock and are likely to be suitable for individual farmers to grow and feed, reducing the complexities of supply associated with marine alternatives."
The next step would be to seek funding to assess whether Montia australasica is a safe feed for cattle, research that could take as little as six to 12 months.
