On a barren hillside in southwest Iceland, workers are installing huge fans to suck carbon dioxide from the air and turn it to stone deep below ground, in a radical - but expensive - way to fight global warming.
Engineering fixes for climate change are gaining attention and investments in 2021 as companies such as Microsoft and leaders from China, the United States and the European Union work on long-term plans to achieve “net zero” emissions goals.
Elon Musk, chief of Tesla Inc and a billionaire entrepreneur, said in January he would give a $100 million prize for the best “technology for capturing carbon”.
Swiss firm Climeworks, which is building the Icelandic site with Carbfix, a unit of Reykjavik Energy, says every technological fix is needed to limit what US President Joe Biden calls a “climate crisis”.
But critics say "direct air capture" (DAC) of emissions already in the atmosphere is too costly, particularly compared to simply reducing emissions, or protecting existing forests and planting new trees.
As they grow, trees soak up carbon dioxide from the air, lowering the amount of carbon in the atmosphere - and old trees are much more effective at it than new plantations, scientists say.
“We should plant as many forests as we can and protect as many as we can. But we are beyond the 'either/or',” in choosing how to slow warming, said Jan Wurzbacher, director and co-founder of Climeworks.
The company is installing eight carbon collectors – each roughly the size of a shipping container – to expand a plant in Iceland that now catches and stores 50 tonnes of carbon dioxide a year, raising its capacity to 4,000 tonnes annually.
Fans suck in air and specialized filters extract the carbon dioxide. Carbfix combines the carbon with water, forming a mild acid that is then pumped 800 to 2,000 meters below ground into basaltic rock.
Within 2 years, 95% of what was carbon dioxide is petrified - turned to rock, said Edda Sif Aradóttir, CEO of Carbfix.
But carbon dioxide makes up only about 0.04% of the air and the process of capturing and storing it is complex and energy intensive, viable in Iceland largely because of a huge, cheap supply of geothermal energy.
U.S. payments company Stripe said last year it would pay Climeworks $775 a tonne for extracting 322 tonnes of carbon dioxide from the air - one indication of the cost.
Microsoft similarly said in late January it would invest in Climeworks to bury 1,400 tonnes of carbon - but Climeworks declined to give the price per tonne.
“Climeworks' direct air capture technology will serve as a key component of our carbon removal efforts,” Elizabeth Willmott, Microsoft's carbon removal manager, said in a statement.
Microsoft said last year that the company will be "carbon negative" by 2030 - removing more emissions than it creates each year - and would by 2050 "remove from the environment all the carbon the company has emitted either directly or by electrical consumption since it was founded in 1975”.
Other firms working on sucking carbon from the air include Carbon Engineering, based in Canada, which says it and its partners are working to build DAC facilities to capture a million tons of carbon dioxide a year.
That is "equivalent to the work of 40 million trees," according to the company, which makes fuels from carbon dioxide.
U.S.-based company Global Thermostat, meanwhile, works with companies including Coca Cola, which uses carbon dioxide to make fizzy drinks, and oil giant Exxon Mobil, which ranks among the world's top corporate emitters of planet-heating emissions.
Climeworks says it is the first to extract carbon from nature permanently, by burying it underground.
Besides its plant in Iceland, it also operates a facility in Switzerland capable of capturing up to 1,000 tonnes of carbon dioxide a year from the air. The gas is then sold to local greenhouses to boost plant growth.
High costs are a headache for all DAC firms.
“Getting below $200 (per tonne of carbon dioxide) is an important step,” said Wurzbacher.
That is about the amount California pays in state credits to support low-carbon transport fuels that can be made with air-captured carbon, he said.
A broader $200 per tonne incentive to make fuel for use in cars or trucks could help develop DAC for all uses - including for carbon burial.
Wurzbacher praised companies and countries that were setting goals of net-zero emissions, but said investments, so far, were lagging far behind Climeworks’ ambitions of capturing between 30 and 50 million tonnes a year by 2030.
The company raised about $110 million last year in a financing round, he said - far less than needed to meet its goals.
“Having someone like Elon Musk putting the focus on carbon capture and storage is important… it becomes more mainstream,” Aradóttir said.
After Musk announced his plans for a $100 million prize, Wurzbacher replied on Twitter: "Let’s talk." Musk has not yet spelled out details of his plan.
Aradóttir said turning carbon to stone is a solution that will lock up greenhouse gases for millions of years - far more permanent than planting trees that can suffer logging, land clearance or more frequent wildfires driven by worsening climate change-related drought and heat.
She said she hoped the new plant will be up and running in the spring – meaning April or May in Iceland’s wintry climate – despite disruptions caused by the coronavirus pandemic.
The International Energy Agency (IEA) said in a report last year that 15 DAC plants were in operation worldwide, in Europe, the United States and Canada, together capturing more than 9,000 tonnes of carbon dioxide a year.
But that is a tiny fraction of world emissions - the equivalent of the annual emissions of just 600 Americans, each producing about 15 tonnes of climate-changing pollution.
“More efforts needed,” the IEA report said in a report headline.
A Greenpeace UK report last month was skeptical of DAC technologies saying they were at a "very early stage and extremely expensive."
"Their future availability remains very speculative, although 'silver-bullet' hopes have led to high-profile media coverage,” the report noted.
Direct air capture of carbon used to be lumped together in U.N. scientific reports as a form of geoengineering, or altering earth systems to deal with climate change threats.
That put it alongside more speculative technologies, such as dimming sunlight with a veil of chemicals injected into the stratosphere.
Since 2018, however, DAC has been reclassified as a form of "mitigation," or emissions cuts - and newer science reports suggest some level of increased carbon removal from the atmosphere is now unavoidable, whether by nature or technology.
Petrifying emissions below ground won't work everywhere. About 5% of the continents have bedrock suitable for the process, though vast swathes of the ocean floor could work as well, Aradóttir said.
So far, Carbfix has injected more than 65,000 tonnes of carbon dioxide into the ground since 2014, almost all produced by a geothermal power plant, rather than captured from the air.
Aradóttir said there was no sign the underground space was getting filled up as ever more liquid was pumped down.
Wurzbacher says Climeworks' future DAC plants will probably be named after animals. The new Icelandic plant is dubbed "Orca," for the killer whale - though "Orka," in Icelandic, also means "energy."
“Mammoth” is one suggestion for another plant in Iceland - a much bigger one.