Carbon Capture Plants Could Reverse Climate Change or Make Synthetic Fuel—Pick One
Roopinder Tara posted on July 07, 2020 |
Sucking the carbon dioxide out of the air. How hard can that be?
Climeworks’CO2collection system in Switzerland. (Photo by Mattia Balsamini for The Wall Street Journal.)
Climeworks’ CO2 collection system in Switzerland. (Photo by Mattia Balsamini for The Wall Street Journal.)

There is suddenly a renewed interest in technology that promises to remove carbon dioxide from the air, quickly and easily, and on such a massive scale that it will reverse climate change. Last month, Climeworks, a Swiss company that wants to build CO2 capturing plants all over the world, received a $75 million investment to help it do so.

While the concept of sucking all the CO2 out of the air sounds neat, wonderful and ever so appealing, engineers have a few questions.

We Put COUp…

Mankind has been putting COinto the air since we discovered fire. But a million years ago all our little campfires were not enough to matter. Relatively recently (in geologic terms, 12,000 years ago), as hunter-gatherers were giving way to farmers, we discovered burning forests to clear land for agriculture was easier than chopping down the trees. Suddenly, we were able to release carbon into the air on a massive scale. Scientists mark that era as the first time that humans were able to change the climate. The Industrial Revolution, 150 years ago, is merely the point when we stepped up the pace at which we added greenhouse gases[1] by burning fossil fuels. Slash-and-burn techniques to clear land for the production of food continues to the present day and accounts for 6 percent of greenhouse gas emissions, according to the Center for Climate and Energy Solutions. The biggest contributor by far is the burning of fossil fuels, which accounts for 72 percent of greenhouse gas emissions.

Greenhouse gas emissions for major economies. Note that emissions in China and India are on the rise. (Image courtesy of the Center for Climate and Energy Solutions.)
Greenhouse gas emissions for major economies. Note that emissions in China and India are on the rise. (Image courtesy of the Center for Climate and Energy Solutions.)

We Can Take It Down

While greenhouse gases are a known problem, the world at large seems unable to put the brakes on burning fossil fuels fast enough, and climatologists worry that even if a concerted global effort is mounted to reverse climate change, will it be in time to avert ecological disasters and stop rising ocean water that already threaten coastal populations? Can we hold our breath long enough for renewable energy to make a difference?

Will it be technology to the rescue? Direct air capture certainly could be quicker than waiting for countries to see the light.

For a long time, we have known that liquids can absorb CO2. The food industry lets water absorb COto give soft drinks their fizz. Industrial processes use aqueous ammonia and monoethanolamine (MEA). NASA used little canisters filled with lithium hydroxide for the Apollo missions.

However, less energy and chemical intensive techniques are being introduced. One discovered by MIT researchers uses charge/discharge cycles of stacks of electrodes coated with polyanthraquinone–carbon nanotube composite. This technique creates CO2 using 1 gigajoule per ton of CO2, compared to industrial methods in existence that vary between 1 and 10 gigajoule per ton, depending on the concentration.

“All of this is at ambient conditions—there’s no need for thermal, pressure, or chemical input,” said MIT postdoc Sahag Voskian, who developed the technique while working on his PhD. “It’s just these very thin sheets, with both surfaces active, that can be stacked in a box and connected to a source of electricity.”

The MIT researchers have created Verdox to commercialize the process and plan to develop a pilot-scale plant in the next year.

Two companies, the aforementioned Swiss Climeworks and British Columbia’s Carbon Engineering, have jumped to the forefront, with direct air conversion (DAC) plants already in operation.

While the two companies produce the same product, their customers and investors could not be further apart. Occidental Petroleum has teamed up with Canada’s Carbon Engineering to create a plant in Texas that will produce a million tons of CO2 per year using potassium hydroxide and other chemicals. When completed in 2023, it will be the largest DAC facility ever. Other investors include Chevron and BHP, an Australian mining company.

Oil companies are big users of CO2, using it for enhanced oil recovery techniques, though most of them get gas from the ground.

The founders of Climeworks, who skied on the slopes of the pristine Swiss Alps and observed the receding glaciers, refuse to sell their CO2 to those they feel are responsible for putting CO2 into the air. “We see at least a strong danger of a moral hazard here,” said Jan Wurzbacher, CEO and cofounder of Climeworks AG, to the Wall Street Journal. “Will it just allow us to emit more fossil fuels?”

The concept of the modular CO₂ collector and a working prototype is developed. (Image courtesy of Climeworks.)
The concept of the modular CO₂  collector and a working prototype is developed. (Image courtesy of Climeworks.)

Climeworks’ proof of concept is a massive array of fans and modules on top of a waste-incineration plant (consistent with the founders’ refusal to work with fossil fuel companies) in Hinwil, Switzerland. Air is blown over an absorbing material with granules that bind with CO2. Hot air from the incinerator will release the CO2, according to the New York Times.

How Much?

Carbon Engineering will not disclose the cost of its Texas carbon capture facility. But we know that carbon capture is not cheap. It costs between about $80 and $160 a metric ton to capture and store CO2 where it is plentiful (like natural gas power plants), but it can cost as much as $450 a metric ton with current technology to extract COwhere it is scarce (like out in the atmosphere), according to Goldman Sachs.

Why Not Recycle Carbon?

Carbon Engineering, attuned to its investors, which include oil and gas companies, proposes adding the CO2 to oxygen and carbon to remake synthetic hydrocarbon fuels—recycling CO2 rather than just throwing it up there.

We are reminded of the second law of thermodynamics, which states that the disorder in the universe can only increase. As everything we do takes energy and results in heat, every attempt to go in reverse—to drive heat into a process—requires energy. How expensive, energy-wise, will this round trip be?

Using a waste product of combustion to make more of the same waste product and selling it as an environmental circle of life may be enough to make environmentalists gag. We’re thinking of the makers of Planet of the Humans, the recent documentary film that questions the virtuosity of the green-tech industry in general and casts doubt on its ability to reduce our reliance on fossil fuels.

While the idea of vacuuming up the air with huge banks of fans sounds energy-intensive and using a chemical process hardly sounds very green, a lot of well-intentioned environmentalists have jumped on direct air capture as the easy method to reverse the trend in global warming. Bill Gates is an investor in Carbon Engineering, for example.

Why Look for CO2 Where You Know It Isn’t?

If you are looking for CO2, shouldn’t it occur to you to look for it where it was most concentrated? That would be in smokestacks or tailpipes in big cities, or perhaps ring big cities, where CO2 is most concentrated. Despite the attention paid to COin the atmosphere, there’s actually very little there by volume. Whereas 21 percent of the air is oxygen, only 0.03 percent is CO2. This means gathering CO2 out in the country is very inefficient.

Could Carbon Capture Wipe Out Plants in the Vicinity?

Sucking all the COfrom the air could be as bad for plants as sucking the oxygen out of the room for humans. Remember the little bit of botany you learned in biology: we inhale oxygen and exhale carbon dioxide; plants inhale carbon dioxide and exhale oxygen.

Carbon Capture Should Be an Easy Sell

Carbon capture is an easy concept to sell. We could think of it as giant batteries of fans all over the Earth, scrubbing the air clean. How hard could that be? We have the technology. Now it’s just a matter of scaling, right?

Visions of air scrubbers out in the country, cleaning up what the cities have emitted, sounds like the idea for our times. Now, if we could provide carbon capture plants with clean energy, perhaps solar, wind… wouldn’t that be the solution?

A number of entities are prepared to invest in carbon capture companies like Climeworks and Carbon Engineering. These include environmentally minded philanthropists, governments anxious to provide an answer and energy companies pressured to emit less CO2.

Carbon capture companies will extract the greenhouse gases out of the atmosphere, where it does harm, and put it where it can do some good—literally greenhouses. In fact, Climeworks lists greenhouses as customers for its CO2. However, we do not know if excess COin greenhouses will make bigger tomatoes any more than excess oxygen in poultry farms will make bigger chickens.

References



[1] The main greenhouse gases are carbon dioxide, with 76 percent of the global man-made greenhouse gas emissions; methane, with 16 percent; and nitrous oxide, with 6 percent, according to the Center for Climate and Energy Solutions.


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