Carbon dioxide removal: the other solution to the climate crisis

cleaning up carbon dioxide

While the world struggles to end greenhouse gas pollution, a handful of innovators are developing ways to clean it up. Their efforts could reverse climate change.

The atmosphere is a true marvel of physics and engineering. Oxygen and ozone prevent dangerous, high frequency gamma, x-ray and ultraviolet radiation from reaching the earth’s surface. Nitrogen and oxygen meanwhile block harmful, fast-moving cosmic rays from deep space. However, the atmosphere allows the visible, life-giving frequencies of sunlight to pass through a kind of window. The sunlight is absorbed by the earth’s surface and beamed outward as infrared radiation, or heat.

Atmospheric transparency to electromagnetic radiation
Atmospheric transparency to various wavelengths of electromagnetic radiation. Click to enlarge. Image source: NASA

While providing a protective shield, the atmosphere also maintains temperatures ideal for life. Carbon dioxide, water vapor and methane absorb and disperse the heat radiating from the earth’s surface. This produces the so-called “greenhouse effect”. Without these naturally occurring heat trapping gases, average global temperatures would be about 30 °C colder.

Increasingly, the greenhouse gases (GHGs) produced by human activity are amplifying the heat-trapping properties of the atmosphere, with the now-familiar apocalyptic symptoms: frequent extreme storms, widespread severe drought, wildfire of unprecedented scale, rapidly melting glaciation, and rising sea levels.

The cause and effect of greenhouse gas pollution has become so obvious that the climate crisis can now be summarized in stark terms: Greenhouse gas pollution is dangerously warming the atmosphere. The appropriate response now seems equally obvious: Stop greenhouse gas pollution. Clean it up.

silver bullet

Ways and means

Until recently, the international response to climate change has focused on stopping GHG pollution. Those efforts continue to move along three basic pathways: replacing machinery that burns fossil fuels with devices that run on electricity or zero carbon energy such as wind, solar and geothermal; discontinuing the use of certain industrial chemicals containing fluorine; and reforming land use practices. This has proven to be a complex international undertaking. System change and countless individual actions are required within these spheres of economic activity. Getting all the players in the affected sectors to cooperate in the context of a competitive, bottom-line-oriented world economy is time-consuming. We are likely decades away from a carbon-neutral world if stopping pollution remains the primary goal.

So zero carbon strategies are broadening to include the cleanup of an estimated 1.5 trillion tonnes of carbon dioxide that have accumulated in the atmosphere since the industrial revolution. Compared to eliminating a multitude of GHG sources worldwide, cleanup scenarios are, practically speaking, simple and straightforward: remove carbon dioxide from the atmosphere, permanently and safely store it, and use some of the CO2 or its derivatives as a valuable industrial material. The politics are simpler too. Removing pollution does not require international cooperation. It has zero disruptive effect on the economic status quo. It’s a wide-open field with no industrial incumbents needing to be replaced or shut down. A handful of technologies deployed globally by well-funded public or private organizations could do the job.

Carbon dioxide pollution accounts for about 75 percent of global greenhouse gas emissions. It is also the only greenhouse gas for which there are proven methods of removal. These methods are categorized by the Intergovernmental Panel on Climate Change as “negative emissions”, or carbon dioxide removal (CDR). Distinct from removing CO2 from the flue gas of an industrial plant, CDR removes carbon dioxide directly from the atmosphere. This can be achieved by direct air capture (DAC) technologies and by the enhancement of natural carbon sinks such as soils and surface geology. The captured CO2 can be stored in geological formations, sold to fizzy drink makers, or broken down into oxygen gas and solid carbon, a valuable industrial material.

Carbon dioxide removal is a pragmatic and perhaps overdue shift in climate change thinking and strategy. In an article published in Issues in Science and Technology, Dr. Klaus Lackner and Christophe Jospe re-frame climate change as a waste management problem. “Carbon dioxide emissions represent the metabolic by-product of industrial activities on which billions of people depend to survive and thrive. Now we must learn to safely dispose of this by-product,” they write. While Lackner and Jospe stop short of calling CDR a panacea, they do identify its key role in eliminating greenhouse gas pollution.

Arizona State University’s Klaus Lackner discusses removing CO2 from the atmosphere.

“Direct air capture will not be a silver bullet that all by itself stops climate change, but it has many assets that can directly address some of the key obstacles to technical, political, and economic progress on climate change,” they write. The scalability and relative simplicity of DAC could ensure that “whatever goes into the atmosphere also comes out, no matter how difficult it is to reduce emissions from particular technologies or sectors, such as transportation. Direct air capture with carbon storage can also, if necessary, lower the carbon dioxide concentration in the atmosphere much faster than natural processes would.”

Klaus Lackner
Klaus Lackner

Klaus Lackner is the director of the Center for Negative Carbon Emissions at Arizona State University and a pioneer in developing DAC since the mid 1990s. His co-author, Christophe Jospe, is Chief Development Officer at Nori, a Seattle-based company that focuses on carbon storage and usage. Nori treats CO2 as a raw material and connects COsuppliers with CO2 buyers. Storing carbon dioxide will entail significant cost, so treating it as a raw material is crucial. In other words, valuable products, derived from captured CO2, could finance a good part of a global cleanup operation.

Diverse pathways, a single purpose

A number of forward-looking organizations, with financial support from government and private investors, are making carbon dioxide removal a reality using DAC and enhanced mineralization processes. They are using CO2 to make stronger concrete, or using it as a feed stock for ultra strong carbon materials. They are combining it with hydrogen to make synthetic fuels, or permanently sequestering the gas.

mechanical trees
Mechanical trees

Silicon Kingdom Holdings, (SKH) based in Dublin, Ireland, is planning to build mechanical tree farms using the capture technology developed by Dr. Lackner. Thousands of times more efficient than natural trees, the devices use anion exchange membranes to remove CO2 from ambient air. A sodium carbonate solution and heat further separate and purify the gas. The CO2 is then pressurized and made available for sequestration or for use in a variety of industrial applications such as synthetic fuels and high strength materials. SKH was established by a group of business and science innovators, including Dr. Lackner, in association with Arizona State University.

Carbon Engineering is making sustainable near-zero-carbon aviation fuel.

Carbon Engineering, based in Squamish, Canada, has designed modular devices that blow ambient air over a capture solution. A closed loop series of chemical processes fixes CO2 and releases it in concentrated form. The firm plans to build full-scale DAC plants to capture a million tonnes of CO2 annually at about $US100 a tonne. The CO2 will be permanently stored underground or combined with hydrogen to make synthetic transportation fuel. Carbon Engineering recently received a $25 million repayable investment from the Government of Canada’s Strategic Innovation Fund and has secured over CA$100 million from private investors including Murray Edwards and Bill Gates. The firm is partnering with 1PointFive in the US and Pale Blue Dot in the UK to finance and build commercial DAC plants.

Climeworks air capture units
Modular air capture units. Image source: Climeworks

Climeworks of Switzerland is operating a demonstration plant near Zurich that can remove 900 metric tonnes of CO2 from the atmosphere yearly. Similar to Carbon Engineering’s technology, fans blow CO2 through modular units roughly the size of shipping containers. Filters in the units capture the gas, then release it for collection. A small demonstration plant in Troia, Italy, will collect 150 tonnes of CO2 per year. Similar to Carbon Engineering’s process, the CO2 is combined with hydrogen to produce synthetic fuel.

CarbFix core sample
A core sample from an injection site showing CO2 bearing carbonate minerals in basaltic host rock. Photo: Sandra O Snaebjornsdottir.

Climeworks also permanently sequesters carbon dioxide underground. In 2019, the organization introduced a public removal and sequestration scheme in partnership with Reykjavik Energy of Iceland. Through its subsidiary CarbFix, Reykjavik Energy injects CO2 from a 303 MW geothermal power plant into subsurface basalt rock. The injected CO2 mineralizes into solid carbonate rock in less than two years. The Climeworks website invites individuals and organizations to pay a monthly subscription – in amounts up to €2,000 per month – to help fund the project. For example, €5 per month will sponsor the sequestration of 61 kilograms of CO2 yearly.

Globally, the storage capacity of basalt is immense. The rock composes about 10 percent of the earth’s continental surface area and underlies most of the planet’s ocean floor. The potential mineral uptake of basalt formations is estimated at between 100 and 250 trillion tons – in theory enough to absorb all the excess CO2 in the atmosphere a hundred times over.

CarbonCure uses CO2 to make a higher-strength concrete.

In Halifax, Canada, CarbonCure injects recycled CO2 into cement during the mixing process. The CO2 mineralizes into calcium carbonate and actually strengthens the concrete as it cures. The process permanently fixes CO2 at relatively low cost, and if scaled to the global concrete market, could sequester over 500 megatons of CO2 annually. CarbonCure presently obtains its CO2 from established suppliers such as fertilizer plants and other cement producers. It expects to use CO2 from DAC technologies as they become available. Breakthrough Energy Ventures, established by Bill Gates and a coalition of private investors including Jeff Bezos and Richard Branson, have invested in the company.

Bio-oil by Charm Industrial
Bio-oil destined for sequestration. Source Charm Industrial

In San Francisco, USA, Charm Industrial has a patent pending for a process that produces bio-oil for storage deep underground. Fast pyrolysis converts the carbohydrate compounds in scrap wood, sawdust, and agricultural waste into a stable liquid similar to crude oil. In effect, the company is reversing crude oil extraction and returning carbon to its geological source.

Eric Matzner, co-founder of Project Vesta
Eric Matzner, co-founder of Project Vesta, explains how olivine are used to sequester carbon dioxide. Image sourec: San Francisco Chronicle

Also in San Francisco, Project Vesta, a non-profit venture, captures CO2 by accelerating the natural weathering of rock. Small grains of olivine, an abundant green volcanic mineral, are spread like sand on shallow beach environments. Wave action abrades the olivine, increasing its surface area. In the process, the mineral reacts to atmospheric CO2 and ocean water – the same silicate-to-carbonate chemical reaction as natural weathering. The olivine becomes limestone which collects on the seafloor. Research suggest that applying olivine on just 2 percent of the world’s shallow ocean shelves would remove one year’s worth of annual global CO2 emissions at low cost. A pilot project is underway on a Caribbean beach, but more testing is required to answer questions about safety and viability.

Stripe, the payment software company, has given financial support to Project Vesta, Charm Industrial, Climeworks and Carboncure. Instead of spending money on projects that curtail emissions through carbon offset programs, the company is distributing  US$ 1 million among these four ventures to help remove carbon dioxide from the air.

Turning CO2 into carbon nanofibres. Dr. Stuart Licht at the American Chemical Society

Meanwhile, C2CNT, comprised of a team of researchers and engineers led by Dr. Stuart Licht of George Washington University, is running a demonstration project at a coal-fired electricity generation plant near Edmonton, Canada. The project captures CO2 from flue gas to produce carbon nanotubes. Using electrolysis, the CO2 is split into oxygen and carbon fibres. The fibres can take different forms for different applications. One form, carbon nanotubes, are a hi-tech industrial material used to make aircraft bodies, tennis rackets and other strong lightweight products. The highest quality nanotubes produced by conventional methods can fetch up to $100,000 per kilogram. Another form of carbon, graphene, is suitable for safe, stable sequestration. The C2CNT project is one of 10 finalists in the Carbon Xprize competition awarded US$500,000 to demonstrate technologies that convert CO2 into valuable products. Capital Power, the owner of the generation plant and host of the demonstration project has invested in C2CNT with the aim of removing CO2 from their flue gas.  

A DAC version of the technology would be self-powered using solar thermal and photovoltaic energy. According to Licht’s calculations, full scale deployment in an area about 10 percent the size of the Sahara Desert could reduce atmospheric CO2 concentrations to pre-industrial levels in as little as 10 years.

Technical innovation goes through several stages. Often, it will start in a university lab. It will then attract the interest of private investors. When things begin to take shape, governments will provide grants. There will be a demonstration phase followed by the technology’s entrance into mainstream markets. Once adopted by the marketplace, costs can go down with economies of scale and the development of production efficiencies. The development of DAC has taken that path. The C2CNT project started in a lab at George Washington University and is now working out of the Genesee generating station, near Edmonton, Canada. When Climeworks’ technology became commercially available in 2014, it captured carbon dioxide for about US$600 per tonne. It now expects to bring costs down closer to US$100 per tonne in two or three years. Carbon Engineering appears to have beaten them to the punch. In 2019 it announced that its fully demonstrated DAC technology was capable of capturing and purifying atmospheric carbon dioxide for under US$100 per tonne.

With CDR, investors like Bill Gates may realize that the near-term cost of cleaning up carbon dioxide pollution is the most pragmatic way to avoid the even costlier long-term effects of the pollution. Capital power, meanwhile, has invested in the C2CNT project in order to continue burning coal to generate electricity. It aims to stop CO2 emissions and pay for the cost of doing so by selling high-value carbon nanotubes derived from those emissions.

As we confront the deepening climate crisis, it helps to remember that we are facing a greenhouse gas pollution crisis, or perhaps less dramatically, a waste management challenge. As we meet that challenge by stopping the pollution at source and removing anthropogenic carbon dioxide from the atmosphere, we can expect things to cool down.

Energy transition – it’s not that complicated

no fossil fuel combustion

Political discourse regarding the global transition to a low carbon economy often presents competing strategies: system change, wind down fossil fuel production, usher in a Green New Deal, block oil pipeline construction, implement carbon taxes, de-grow the economy. There is an unsettling lack of focus and practicality. However, common to all points of view is the undeniable necessity of energy transition. and while energy systems are indeed complex, and replacing them on the fly is a singular challenge, the principles underlying energy transition itself are fairly straightforward. Here are some key things to remember.

1) We stop GHG pollution by means of energy transition

Carbon dioxide accounts for up to 75 percent of anthropogenic greenhouse gases and is produced almost entirely by the world’s inventory of coal-fired electricity plants, gasoline powered automobiles, cement plants, steel mills, home oil furnaces, gas stoves, and gas powered hand tools.

We end carbon dioxide pollution by replacing these technologies. The replacements, largely powered by electricity, are mature, proven, and rapidly becoming cost competitive.

While energy transition aims to stop carbon dioxide pollution, the cleanup part is equally important. A number of technologies are in the works for “negative emissions” – that is, ways and means to remove accumulated CO2 directly from the air. One of them is at the demonstration stage. Another, the STEP process is in development in a lab at George Washington University, and may be capable of capturing and disposing of carbon dioxide at the volume and speed necessary to prevent catastrophic warming of the atmosphere.

2) All energy transition strategies have a common goal: replace fossil fuel-based energy conversion devices

It’s early in the game, but zero carbon outcomes are being pursued now in four energy-intensive sectors of the global economy: electricity generation, transportation, heavy industries (such as cement and steel manufacturing), and building/home operations. To stop carbon dioxide pollution, each sector is taking steps to replace the specific technologies that produce said pollution. For example, the automotive industry is replacing internal combustion engines with electric motors in the aggregate fleet of about a billion motor vehicles worldwide. One innovative company is offering retrofit electric drive systems for existing vehicles. Grid operators around the world will eventually retire several thousand coal, oil or natural gas-fired steam turbines, along with the facilities that house them. They are to be replaced with wind turbines, solar arrays, geothermal plants, or fourth generation nuclear reactors.

The guiding principle is to replace energy conversion devices (ECDs) that emit carbon dioxide pollution with ECDs that do not. Complex infrastructure, transmission systems, and processes built around all such devices are added, replaced or modified accordingly.

3) Industrial initiative is at least as important as political will

Energy transition policy is formulated in board rooms and factories as much as in the offices of government. Automobile manufacturers build electric propulsion systems. Electric utilities install solar panels and wind turbines designed and built by multinational corporations. The role of bureaucrats and elected officials is to work with these private sector entities and do everything possible to foster industrial initiative, innovation and market diffusion of their zero-carbon energy devices and systems.

4) Energy transition is a phase out / phase in process

Energy transitions have happened before. In the last century, internal combustion engines replaced horses, and diesel-electric locomotives replaced coal-fired steam engines. Such transitions were spontaneous and occurred at their own pace, with little or no social disruption, and were usually confined to one economic sector.

The 21st Century rendition of energy transition is different to the extent that it reaches into all energy-intensive sectors in all industrial economies. At the same time, it is sharply delineated, aiming specifically to replace the deeply rooted, fossil fuel-based devices that power the modern world.

There is a time element involved, a phase-out/phase-in process taking place. This requires careful management of energy systems so they there is energy available to effectively carry out transition. Energy supplies must be maintained for the outgoing system as well as the incoming system. For a while, pipelines will coexist with EV charging stations. It looks bad, but it’s not.

The role of government

Governments that design policy to support private sector energy transition can be confident they are on track. China, the UK and a few other jurisdictions have already set dates for phasing out internal combustion engines in automobiles. The state of Oregon changed public utility regulations to allow the sale of electricity at roadside EV charging stations. If industry doesn’t take the hint, governments may have to go further. Phasing in zero-carbon ECDs at the maximum possible speed may require the kind of direct industrial control that occurred during mobilization at the outset of two world wars. Whatever happens, sustained clear-headed cooperation among government, the people, and the globalized private sector is necessary.