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Floating in the Port of Los Angeles, a strange-looking barge covered in pipes and tanks holds a concept scientists hope to make waves: a new way to use the ocean as a vast carbon dioxide sponge to tackle global warming.
Scientists at the University of California Los Angeles (UCLA) have been working for two years on SeaChange, an ambitious project that could one day increase the amount of CO2, a major greenhouse gas, that can be absorbed by our seas.
Their goal is “to use the ocean like a big sponge,” according to Gaurav Sant, director of the university’s Institute for Carbon Management (ICM).
The oceans, which cover most of the Earth, are already the planet’s major carbon sinks, serving as a critical buffer in the climate crisis.
They absorb a quarter of all CO2 emissions, as well as 90 percent of the warming that has occurred in recent decades due to rising greenhouse gases.
But they feel the tension. The ocean is acidifying and rising temperatures reduce its absorptive capacity.
The UCLA team wants to increase that capacity by using an electrochemical process to remove large amounts of CO2 already present in seawater, a bit like squeezing a sponge to recover its absorbency.
“If you can get rid of the carbon dioxide that’s in the oceans, you’re essentially renewing their ability to absorb additional carbon dioxide from the atmosphere,” Sant told AFP.
– Trapped –
Engineers built a floating mini-factory on a 30-metre-long boat that pumps seawater and subjects it to an electrical charge.
Chemical reactions triggered by electrolysis convert CO2 dissolved in seawater into a fine white powder containing calcium carbonate, the compound found in chalk, limestone and the shells of oysters or mussels.
This dust can be thrown back into the ocean, where it remains in solid form, thus storing the CO2 “very durably … for tens of thousands of years,” Sant explained.
Meanwhile, the pumped water returns to the sea, ready to absorb more carbon dioxide from the atmosphere.
Sant and his team are confident the process won’t harm the marine environment, though that 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 in the future.
Of course, the priority in curbing global warming is for humans to drastically reduce current CO2 emissions, something we are fighting to achieve.
But in parallel, most scientists say that 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 industries that are particularly difficult to decarbonise, such as aviation and cement and steel manufacturing.
It could help tackle CO2 stocks that have built up in the atmosphere for decades.
– “Promising solution” –
Controlling global warming will require removing between 450 billion and 1.1 trillion tonnes of CO2 from the atmosphere by 2100, according to the first global report on the topic, released in January.
This would require the RDF sector “to grow at a rate of about 30% annually over the next 30 years, just as has happened with wind and solar,” said one of its authors, Gregory Nemet.
UCLA’s SeaChange technology “fits in the category of a promising solution that could be big enough to be relevant to the climate,” said Nemet, a professor at the University of Wisconsin-Madison.
By sequestering CO2 in mineral form within the ocean, it differs markedly from existing ‘direct air capture’ (DAC) methods, which involve pumping and storing the gas underground in a highly complex and expensive process.
A start-up company, Equatic, plans to scale up the UCLA technology and demonstrate its commercial viability by selling carbon credits to manufacturers who want to offset their emissions.
In addition to the Los Angeles barge, a similar boat is currently being tested in Singapore.
Sant hopes the data from both sites will quickly lead to the construction of much larger plants capable of removing “thousands of tons of carbon” each year.
“We expect to start operating these new rigs in 18 to 24 months,” he said.
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