Carbon dioxide removal: a silver bullet to stop climate change

a climate change silver bullet

Energy transition and land-use reform will someday contain greenhouse gas pollution. Meanwhile, it’s time to clean up the mess.

The earth’s protective atmosphere is a marvel. Oxygen and ozone absorb high-energy gamma rays, x-rays and ultraviolet light, preventing them from reaching the earth’s surface. However, life-sustaining visible radiation from the sun reaches the surface unhindered. Nitrogen and oxygen block fast-moving cosmic rays.

Atmospheric gases also maintain ideal temperatures. Carbon dioxide, water vapor and methane trap and disperse heat radiation given off by the earth’s surface, thereby producing the so-called greenhouse effect. Without it, average surface temperatures would be more than 30 °C colder than they are now.

Inconveniently, greenhouse gases are also produced by industrial activity. And most people now realize that those gases are intensifying the atmosphere’s capacity to trap heat. We therefore regard these anthropogenic greenhouse gases as pollution. Carbon dioxide from fossil fuel combustion accounts for roughly 75 percent of this pollution.

So we are now collectively dealing with a warming atmosphere, more extreme weather, melting glaciation and rising sea levels. In recent decades, the situation has escalated, driven by rapid population growth and industrial development worldwide. As both a planetary event and a pan-cultural narrative, the scale and scope of the situation has become so incomprehensible that many people now wonder what, if anything, can be done about it.

silver bullet aimed at climate change

As it turns out, economic activity is beginning to adjust. The transportation, electricity generation, heavy industry, and building sectors worldwide have begun to reduce carbon dioxide pollution by replacing fossil fuels as their source of mechanical and heat energy. The agriculture and forestry sectors are making incremental moves toward land use reform – that is, reducing destructive human impact on natural habitat and cultivated land – in order to reduce emissions of nitrous oxide, methane and carbon dioxide. Steel and cement producers have begun to employ low carbon manufacturing processes, and manufacturers have begun the phase-out of certain fluorine-based chemicals. For its part, the general public recognizes the importance of taking public transit, eating less meat, and making homes more energy efficient.

Nevertheless, climate action remains a nebulous and sometimes contentious affair. Solutions seem too distant to address the immediacy of catastrophic drought, wildfires and flooding worldwide. Practical climate solutions are almost entirely dependent on structural changes in the competitive world economy and constrained by the appetite governments may or may not have to use policy instruments to expedite those changes. Most challenging, perhaps, is the fact that the electricity, transportation, industrial, building and land use sectors of the world economy must, to some degree, overcome path dependence. This means that in order to cut pollution, familiar ways of doing things must be put aside or dismantled at significant cost. Unfortunately, there is not enough time to let these otherwise normal transition processes work themselves out.

Just as cultural narratives frame how we think and act in general, the prevailing climate narrative frames the way think and act regarding climate action. The political version of the narrative, rooted in the UN Framework Convention on Climate Change of 1992, calls for reductions in greenhouse gas emissions, jurisdiction by jurisdiction, in a way that doesn’t involve undue economic hardship. This framework has been overtaken by events.

An estimated 1.5 trillion tonnes of anthropogenic carbon dioxide have accumulated in the atmosphere since the industrial revolution, although some of it has, over time, been absorbed by the oceans, land surface and vegetation. The rate of the pollution has accelerated sharply in recent decades with an estimated 35 billion tonnes being emitted annually worldwide. The destructive effects can be stated in stark terms: greenhouse gas pollution is dangerously warming the planet. The solution is correspondingly direct and urgent. Stop greenhouse gas pollution. Clean it up. All hands on deck.

Ways and means

In practical terms, stopping greenhouse gas pollution and cleaning it up are two distinct action pathways. The first pathway, stopping the pollution, involves ending the use of energy conversion devices that burn fossil fuels, ending the use of certain industrial chemicals containing fluorine, and revising 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 a challenge in itself; ergo, exceedingly time consuming.

In contrast, cleaning up GHG pollution is relatively simple and straightforward, both conceptually and in practice. Remove carbon dioxide from the atmosphere. Permanently and safely store it. Use some of the CO2 as an valuable industrial material. Conceivably, one technology deployed globally would do the job.

Cleaning up GHG pollution is defined by the Intergovernmental Panel on Climate Change (IPCC) as carbon dioxide removal (CDR). Note that it is distinct from the removal of concentrated CO2 from the flue gas of an industrial plant which, strictly speaking, is a form of pollution prevention. With CDR, accumulated CO2 is removed directly from the atmosphere at a practical and convenient geographical location. Removal may occur in two ways: by direct air capture (DAC) technologies, and by the enhancement of natural carbon sinks such as soils and surface geology. The captured CO2 may be dealt with in two ways as well: sequestered, or converted into a valuable industrial material such as graphene.

Carbon dioxide removal directly addresses accumulated greenhouse gas pollution and represents a conceptual shift in climate change avoidance tactics. In an article published in Issues in Science and Technology in 2017, Dr. Klaus Lackner and Christophe Jospe re-framed 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 don’t regard CDR as a panacea, they do identify its crucial role in eliminating greenhouse gas pollution.

“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 continue. The scalability and relative simplicity of DAC, coupled with storage and utilization (DACSU) 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 is the director of the Center for Negative Carbon Emissions at Arizona State University. Since 1995, he has been a pioneer in developing DAC. Christophe Jospe is Chief Development Officer at Nori, a Seattle-based company that treats CO2 as raw material, connecting COsuppliers with CO2 buyers. 

Treating COas a raw material – either for sequestration or as the basis of an industrial product – is the key concept behind the development and deployment DACSU technologies. Valuable products, derived from captured CO2, would offset the high costs of deploying the critically important global cleanup operation.

Diverse pathways, a single purpose

A number of forward-looking organizations are beginning to make carbon dioxide removal a reality using enhanced natural processes and direct air capture. Some techniques find immediate use for captured CO2 in concrete, ultra strong carbon materials or synthetic fuels. Other developers are finding ways to permanently sequester the gas.

Silicon Kingdom Holdings, 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, mechanical trees use anion exchange membranes to remove CO2 from air flowing through them. Sodium carbonate solutions 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.

In Squamish, Canada, Carbon Engineering uses modular devices that blow air over a liquid capture solution. A closed loop series of chemical processes fixes the CO2 and then release it in concentrated form. Carbon Engineering plans to build full-scale modular plants that capture a million tonnes of CO2 annually. The CO2 will be permanently stored underground or combined with hydrogen to make synthetic transportation fuel.

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, fans blow CO2 through modular capture units roughly the size of shipping containers. Filters in the units capture the gas, then release it for collection when heated. A smaller demonstration plant in Troia, Italy, will collect 150 tonnes of CO2 per year. Again, similar to Carbon Engineering’s process, the CO2 is combined with hydrogen to produce synthetic fuel.

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. In less than two years, the injected CO2 mineralizes into solid carbonate rock. 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 potential 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. Globally, 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.

In Halifax, Canada, CarbonCure injects recycled CO2 into cement during the mixing process. The carbon dioxide 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 derives most of its CO2 from industrial emitters such as ethanol, fertilizer, or other cement plants. In the future it expects to use CO2 from DAC technologies as they become available.

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.

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.

In Calgary, Canada, a team of researchers led by Dr. Stuart Licht of George Washington University is running a demonstration project that uses electrolysis to capture CO2 from flue gas to produce carbon nanotubes (C2CNT). The CO2 is split into pure oxygen and pure carbon fibres. The fibres can take different forms for different applications. Graphene would be suitable for safe, stable sequestration. Carbon nanotubes, a hi-tech industrial material, are now used to make aircraft bodies, tennis rackets and other strong lightweight products. The highest quality nanotubes can fetch up to $100,000 per kilogram. Direct air capture versions of the process would be self-powered using solar thermal and photovoltaic energy. According to Licht’s calculations, full scale deployment in an area less than 10 percent the size of the Sahara Desert could reduce atmospheric CO2 concentrations to preindustrial levels in 10 years.

At present, capturing, using and sequestering carbon dioxide by any means is expensive, costing up to $600 per tonne and more. However, and as with any new technology, economies of scale could put the cost below $100 per tonne.

Normally, fishing around in the turbulent waters of the world economy for a silver bullet to stop climate change would be a fool’s errand. Nevertheless, the global application of CDR is a potentially decisive pathway to ending the now-manifest effects of greenhouse gas pollution. As we fret about the deepening climate crisis, it helps to remember that the climate crisis is a greenhouse gas pollution crisis, or perhaps less dramatically, a waste management challenge. It is both reasonable and scientific to expect the spectre of climate change to vanish when we remove all anthropogenic carbon dioxide from the atmosphere. It can be done.