Scientists and engineers have pumped 300 litres of simulated whale poo into the ocean off Sydney as part of efforts to snag a share of Elon Musk's US$100m prize for capturing and storing carbon.
The team, known as WhaleX, carried out its first open-ocean experiment on Sunday about eight kilometres off Port Botany in New South Wales after gaining clearance from the federal government.
The 12-strong team are racing to carry out a follow-up experiment using up to 2000 litres of the simulated poo - a mix of nitrogen, phosphorus and trace elements - before the end of January.
Tesla and SpaceX founder Musk announced in February he was funding a US$100m competition through the XPrize Foundation to find methods that could safely capture and store carbon dioxide at a scale of a billion tonnes or more a year.
Musk said at the time the competition was not "theoretical" but was looking for teams that could "build real systems that can make a measurable impact and scale to a gigaton level."
WhaleX registered for the four-year competition and will send a report before February hoping to be selected for one of up to 15 "milestone" prizes of U$1m each.
Whale faeces is known as an ocean fertiliser and a food for phytoplankton. When phytoplankton grow and multiply, they absorb carbon. When they die, they sink to the ocean floor taking much of the carbon with them.
Dr Edwina Tanner, a climate scientist who is leading the WhaleX project, and colleagues said they targeted a 225sq km area off Port Botany where their previous water sampling had shown a deficiency in nutrients.
From a small boat, the team aerated the formulation with a gel made from seaweed and mixed that with a dye so they could see from a drone how it dispersed.
The formulation, manufactured as an aqua food by a fertiliser company in regional New South Wales, was formulated to match the deficiencies in nutrients in the area where the trial was carried out.
The amount released was about the equivalent of a Humpback whale doing two poos, Tanner said. To be successful, she said the aqua food mix needs to stay in the top 20 to 30m for at least a day.
"It was incredible. The food stayed buoyant and well within the trial zone location," Tanner said.
The team thinks the experiment, which was to test the method used to disperse the formulation and to see how buoyant it was, will have sequestered about two tonnes of carbon dioxide.
Tanner said "a lot of science" would need to be done to make sure the approach is not damaging the marine environment, but she said as it closely mimicked a process that has been happening for millions of years "we're confident we can do this safely."
A further trial is being planned before the end of January and will see up to 2000 litres dispersed from a larger boat in the same area of ocean.
If scaled up, WhaleX would fall into a broad category of carbon reduction efforts known as negative emissions technologies - an approach where more CO2 is sequestered than is used during the process.
WhaleX is looking along whale migration routes for suitable sites for further trials, including near Morocco, Oman and Kenya. An area off Western Australia over the north-west shelf has also been selected.
Managing director of Ocean Nourishment Corporation (ONC) and one of the partners in the project, John Ridley, said work would continue even if it was not successful in the XPrize competition.
He said the process was currently costing about $25 to $30 to sequester a tonne of carbon dioxide.
He said investors were being attracted to it because of the potential scale and, he said, it could store carbon securely and for longer than some land-based methods. ONC was actively speaking with more than 10 investor groups from Europe and Australia.
He said the world's climate crisis was pushing the planet close to "several dangerous tipping points".
"We need emissions reductions and carbon removal and we have to escalate both of those really fast, almost at military scale."
This month the US National Academies of Sciences, Engineering, and Medicine released a report summarising the potential risks and benefits of a range of supposed ocean-based methods to remove and store CO2.
The report said there was medium to high confidence that adding nutrients to the ocean to promote phytoplankton growth could be "effective and scalable".
There was less confidence about the potential environmental risks of the method on a very large scale, but the report said "there are deep-ocean impacts and concern for undesirable geochemical and ecological consequences."
The report added: "No matter what the impact of [ocean fertilisation] on the deep sea, it should be noted that what deliberate and large-scale [ocean fertilisation] would do is essentially speed up the natural processes that are already happening, under any current scenario of enhanced CO2 in the atmosphere."
A department of agriculture, water and the environment spokesperson said it was aware of the WhaleX project and the department had confirmed the experiment could go ahead without the need for any permit.
A statement said the WhaleX trials were "considered to be genuine scientific research" under the London Protocol that covers dumping at sea as it was considered a "placement" of materials.
The statement said: "For future trials involving larger volumes of material, the department has advised WhaleX that additional information would be required for the department to determine whether the activity could still be defined as 'genuine scientific research' under the London protocol."
"If the department considers that future trials are of a scale that cannot be considered to be genuine scientific research, the activity would be considered as dumping under the sea dumping Act."
The spokesperson said the government did not have any policies on ocean fertilisation that would regulate future large scale activities.
But the spokesperson also said: "However, work is under way with reference to Australia's obligations under the London protocol to consider ocean fertilisation as a future regulatory area."
In November, teams of Australian university students at Monash University, the University of Sydney and the University of Tasmania each won a $250,000 prize in the competition for proposed carbon projects. Judges were looking for student projects that would make them "competitive applicants" in the overall competition.
After four years XPrize judges will pick one U$50m grand prize winner and a U$30m prize to go be shared among up to three runners up.
