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October 20, 2021

The windswept valleys surrounding the Hengill volcano in southwestern Iceland are dotted with hot springs and steam vents. Hikers from all over the world come here to witness its breathtaking scenery. Even the sheep are photogenic in the soft Nordic light.

Environmental scientists have designed a towering metal structure resembling four giant Lego bricks, with two rows of six whirring fans running across each one. It's a contraption that looks truly futuristic, like something straight out of a sci-fi film. It is designed to take care of emitted carbon dioxide (CO2) in the atmosphere.  These machines are used to literally suck out the gas, in an attempt to slow the climate crisis and prevent some of its most devastating consequences.

The Orca plant — its name derived from the Icelandic word for energy — is what is known as a "direct air carbon capture facility," and its creators and operators, Swiss firm Climeworks and Icelandic company Carbfix, say it's the world's largest. Climework's Orca project at the Hellisheiði Geothermal Power Plant in Iceland opened last month.

Orca aims at a net-zero emissions world
The aim of Orca is to help the world reach net-zero emissions — where we remove as much greenhouse gas from the atmosphere as we emit. Scientists say that simply cutting back on our use of fossil fuels won't be enough to avert catastrophe; we need to also clean up some of the mess we've been making for hundreds of years.

Orca is a depressing symbol of just how bad things have become, but equally, it could be the tech that helps humanity claw its way out of the crisis. "We, as humans, have disturbed the balance of the natural carbon cycle. So it's our job to restore the balance," said Edda Aradóttir, a chemical engineer and the CEO of Carbfix. "We are assisting the natural carbon cycle to find its previous balance, so for me, at least, this makes total sense — but we have to use it wisely," she said.

It opened last month and currently removes about 10 metric tons of CO2 every day, which is roughly the same amount of carbon emitted by 800 cars a day in the US. It's also about the same amount of carbon 500 trees could soak up in a year.

It's a fine start, but in the grand scheme of things, its impact so far is minuscule. Humans emit around 35 billion tons of greenhouse gas a year through the cars we drive and flights we take, the power we use to heat our homes, and the food — in particular the meat — that we eat, among other activities. All this CO2 accumulates in the air, where it acts like the glass of a greenhouse, trapping more heat in the atmosphere than Earth has evolved to tolerate.

That's where the technology used for Orca, called carbon capture and storage (CCS), comes in. "Carbon capture and storage is not going to be the solution to climate change," according to Sandra Ósk Snæbjörnsdóttir, a Carbfix geologist. "But it is solution. And it's one of the many solutions that we need to implement to be able to achieve this big goal that we have to reach." She added: "First and foremost, we have to stop emitting CO2 and we have to stop burning fossil fuels, the main source of CO2 emissions to our atmosphere."

How the 'magic' happens
The Orca machines use chemical filters to capture the heat-trapping gas. The "fans," or metal collectors, suck in the surrounding air and filter out the CO2 so it can be stored. Carbon dioxide's concentration in Earth's atmosphere has likely not been this high at any other point in the last 3 million years, according to NASA scientists. But at levels over 410 parts per million, to actually capture a meaningful amount of CO2, a huge amount of air needs to pass through these machines.

"What is happening is that CO2 in the air is an acid molecule and inside the collectors we have alkaline. Acids and alkaline neutralize each other," according to Climeworks co-CEO Christoph Gebald. "That's the magic that happens." In two to four hours, the surface of the filter is almost completely saturated with CO2 molecules — as if there are "no parking slots left," as Gebald puts it. "Then we stop the airflow and we heat the internal structure to roughly 100 degrees Celsius, and at that temperature, the CO2 molecules are released again from the surface, they jump off back to the gas phase and we suck it out."

Because of the high temperature that is needed for the process, the Orca plant requires a lot of energy. That's a problem that's easily solved in Iceland, where green geothermal power is abundant. But it could become a challenge to scale globally.
The machines at Orca are just one way to remove CO2 from the air. Other methods involve capturing the gas at the source — like the chimney of a cement factory — or removing it from the fuel before combustion. That involves exposing the fuel, such as coal or natural gas, to oxygen or steam under high temperature and pressure to convert it into a mixture of hydrogen and CO2. The hydrogen is then separated and can be burned with much lower carbon emissions. However, methane emissions could be a problem when the process is used on natural gas.

The carbon that comes out of CCS can be used for other purposes, for example, to make objects out of plastic instead of using oil, or in the food industry, which uses CO2 to put the fizz in drinks. But the amount that needs to be captured vastly exceeds the world's demand for CO2 in other places, which means the majority of it will need to be "stored."

These igloo-like structures are Carbfix's mineralization sites, where C02 is mixed with water and injected around 800 meters underground. At Orca, this happens just a few hundred meters away from its vacuum in several igloo-like structures where the gas is mixed with water and injected around 800 meters underground. There, the CO2 reacts with sponge-like volcanic rocks and minerals, while the water flows away.

Emissions crisis
The latest state-of-the-science report by the Intergovernmental Panel on Climate Change (IPCC) showed that the world needs to cut greenhouse gas emissions in half over the next decade and achieve net-zero by 2050 to have any chance of keeping global warming to 1.5 degrees Celsius above pre-industrial levels.
The higher temperatures rise beyond 1.5 degrees, the more the world will experience an increase in extreme weather events — both in strength and frequency — like droughts, hurricanes, floods, and heatwaves.

Atmospheric concentrations of CO₂
The amount of CO₂ in the atmosphere has fluctuated over time, but human activity since the Industrial Revolution has pushed levels to unprecedented highs. CO₂ concentration measured in parts per million (ppm)