Scientists from the University of California Los Angeles (UCLA) have been working for two years on SeaChange – an ambitious project that could one day boost the amount of carbon dioxide, a significant greenhouse gas, that our seas can absorb.

Floating in the port of Los Angeles, a strange-looking barge covered with pipes and tanks contains a concept scientists hope to make waves: A new way to use the ocean as a vast carbon dioxide sponge to tackle global warming.

Their goal is "to use the ocean as a big sponge," according to Gaurav Sant, director of the university's Institute for Carbon Management (ICM).

The oceans, covering most of the Earth, are the planet's leading carbon sinks, acting as a critical buffer in the climate crisis.

They absorb a quarter of all carbon dioxide emissions and 90% of the warming in recent decades due to increasing greenhouse gases.

But they are feeling the strain. The ocean is acidifying, and rising temperatures are reducing its absorption capacity.

The UCLA team wants to increase that capacity by using an electrochemical process to remove vast quantities of carbon dioxide already in seawater – rather like wringing out a sponge to help recover its absorptive power.

"If you can take out the carbon dioxide in the oceans, you're essentially renewing their capacity to take additional carbon dioxide from the atmosphere," Sant told Agence France-Presse (AFP).

Trapped

Engineers built a floating mini-factory on a 30-meter (100-foot) long boat which pumps in seawater and subjects it to an electrical charge.

Chemical reactions triggered by electrolysis convert carbon dioxide dissolved in the seawater into a fine white powder containing calcium carbonate – the compound found in chalk, limestone and oyster or mussel shells.

This powder can be discarded back into the ocean, where it remains solid, storing CO2 "very durably ... over tens of thousands of years," explained Sant.

Meanwhile, the pumped water returns to the sea, ready to absorb more atmospheric carbon dioxide.

Sant and his team are confident the process will not damage the marine environment, although this will require further testing to confirm.

A potential additional benefit of the technology is that it creates hydrogen as a byproduct. As the so-called "green revolution" progresses, gas could be widely used to power clean cars, trucks and planes.

Of course, the priority in curbing global warming is for humans to reduce current carbon emissions drastically – something we are struggling to achieve.

But in parallel, most scientists say carbon dioxide capture and storage techniques can play an important role in keeping the planet livable.

Carbon dioxide removal (CDR) could help achieve carbon neutrality by 2050 as it offsets emissions from particularly difficult-to-decarbonize industries, such as aviation and cement and steel production.

It could help to tackle the stocks of carbon dioxide that have been accumulating in the atmosphere for decades.

'Promising solution'

Keeping global warming under control will require the removal of between 450 billion and 1.1 trillion tons of carbon dioxide from the atmosphere by 2100, according to the first global report dedicated to the topic, released in January.

That would require the CDR sector "to grow at a rate of about 30% per year over the next 30 years, much like what happened with wind and solar," said one of its authors, Gregory Nemet.

UCLA's SeaChange technology "fits into a category of a promising solution that could be large enough to be climate-relevant," said Nemet, a professor at the University of Wisconsin-Madison.

By sequestering carbon dioxide in mineral form within the ocean, it differs markedly from existing "direct air capture" (DAC) methods, which involve pumping and storing gas underground through a highly complex and expensive process.

A start-up company, Equatic, plans to scale up the UCLA technology and prove its commercial viability by selling carbon credits to manufacturers wanting to offset their emissions.

In addition to the Los Angeles barge, a similar boat is being tested in Singapore.

Sant hopes data from both sites will quickly lead to the construction of far larger plants capable of removing "thousands of tons of carbon" each year.

"We expect to start operating these new plants in 18 to 24 months," he said.