How to Subtract

By Metta Spencer | 2021-12-31 20:00:00

I just took a test on my iPad to measure my current carbon footprint. It was 5.1—better than the 10.1 Canadian average, but worse than the 2.1 that I should achieve to do my part in keeping our planet habitable.

That prompted me to think about the validity of the footprint as a predictive instrument. Can it tell us anything important? I think not, but asking the question did enlighten me about important new developments that I’ll share with you here.

The carbon footprint calculator that I used is obsolete because of the pandemic. For example, I never go out anymore, so I recorded my transportation emissions as zero, but Amazon and Skip the Dishes do deliver things to me, so logically that should count as my own transportation. It did not.

But suppose someone designed a better footprint app. What should it count? Last year The Economist published a fictional story set in a future phase of the climate crisis when people are recording their activities on cell phones and being held accountable for each new addition of carbon to their footprints.1

It supposedly starts with an app that environmentalists install on their cell phones. They start demanding that restaurant menus show, not only the price and the number of calories, but also the amount of carbon that had gone into producing each dish. Presumably these estimates include the carbon required to produce and transport every ingredient in, say, each slice of cherry pie, and washing the plate afterward.

As the yarn continues, Amazon and Alibaba start printing the carbon emission figures for everything they sell. Then all governments start requiring citizens to keep records and fining those who emit more carbon than their limit. Some citizens object that this is totalitarian, but others justify it as necessary during the climate crisis.

I thought it was a cute story. But then I wondered: Could it really be done? And if so, would the total from all cell phones in the world predict the increases or decreases in global warming? Climatologists usually depend on mathematical models, and they made a few fifty years ago that have predicted global warming pretty accurately. However, those models were not based on individual carbon footprints, but on physics and the increasing emissions of greenhouse gas.

If global warming is “anthropogenic”—caused by human individuals—and if all individuals report their emissions on their cell phones, then the total will correlate closely with climate changes. Right?

No, probably not. I found four obvious errors in that assumption, and thinking about it led to some interesting discoveries, which I’ll show later. Let’s start with the four errors.

1. Don’t Forget Group Footprints

The sum of all individual human carbon footprints does not include emissions by organizations and states. My carbon footprint doesn’t include the fossil fuels that heat my church or that build a concrete expressway or the new fighter jets that Canada will buy. These collective emissions probably influence the climate more than those of all individuals put together, but they are not counted against any individual’s carbon footprint.

2. Nature Affects the Climate Too

The model only counts the actions of human beings, though of course nature still determines the temperature more than all of us put together. Volcanoes, trees, ocean currents, and grass fires affect the climate, by emitting or retaining carbon. Even whales are important. I bet you didn’t know this: An average great whale sequesters 33 tons of CO2 in its body and takes it to the bottom of the ocean when it dies, keeping it out of the atmosphere for centuries. There were once 4 or 5 million whales, but now, because of whaling, only 1.3 million. A whale is constantly pumping water up from the depths to the surface, bringing up minerals and excreting iron and nitrogen that feed the phytoplankton. If there were still enough whales to increase the plankton by even one percent, this would capture hundreds of millions of tons of carbon dioxide each year—as much as two billion mature trees capture. And whales live about sixty years, performing these services every year. It is sheer hubris to suppose that humankind is fully in charge of our world’s temperature.2

3. Carbon is Not the Only Determinant of Climate

In fact, there are ways to reduce global warming without changing the amount of greenhouse gas in the atmosphere. How so?

Greenhouse gas is a huge problem because it retains the heat from the incoming sun’s rays. But suppose we could deflect those rays before they could warm the atmosphere—say, by opening a giant umbrella over the earth or putting mirrors in space to reflect the sunbeams before they could heat the atmosphere? This would not affect the greenhouse gas at all but would cool the planet.

There are many such suggestions—including even the mirrors-in-space idea, though that has hardly any support. There would be millions of little mirrors in orbit—a “space junk” hazard to satellites and spacecraft that could not be retrieved after the need passed. I, for one, would reject the mirror proposal as a crackpot plan.

A related approach is based on the known effects of volcanoes. Sometimes a big volcano spews out enormous amounts of sulfur into the stratosphere, where it circles the planet for a year or two, filtering out sun rays. This cools the planet by a degree or more. If we could make it happen deliberately, that would give us more time to transition away from fossil fuels. Instead of a volcano, we’d use airplanes or even a giant tube to shoot sulfur or calcium compounds into the stratosphere. You may worry about side effects that are unpredictable but irreversible. And you should. There’s no way to bring the stuff back down if anything goes wrong.

But the next proposal makes better sense: brighten the clouds. Dark clouds are large, heavy droplets that generally portend rain. White clouds are composed of small droplets, which reflect more sun rays back into space than dark clouds. Hence the plan is to reduce clouds’ droplets to cool the land or sea below them. I’ve interviewed some scientists who are working on the plan, which is actually feasible. The global warming problem could be solved by increasing the reflectivity of the earth by only 0.05%, which can be done.

Professor Stephen Salter is one leader in this research. And in Australia Professor Daniel Harrison’s team is planning to save the corals by spraying salt water into clouds above the Great Barrier Reef. Each droplet contains a tiny “condensation nucleus”—dust or almost anything else—but over the ocean there are few such tiny particles, and the most convenient condensation nucleus there would be salt. Harrison will spray salt water mists, which will quickly evaporate, leaving salt to become the condensation nucleus for a new, tiny, white droplet. But the project has taken several years of preparation and, so far, no nozzles have been able to produce sufficiently small droplets.

If the Australian experiment succeeds, the scheme may move to the global scale. Salter estimates that about 800 spray vessels would be enough to cool the planet. He would put them to the Arctic in the summer, then move them to the tropical oceans during the other months. He estimates the price as £240 million annually, but I can imagine a quicker, cheaper way: Rent some fishing boats or persuade retired couples who own yachts to volunteer. They’d gladly spray salt water to save the planet for their grandchildren. And fortunately, the effects are reversible; if negative consequences arise, just stop spraying and within three weeks the effects will stop too.

While cloud brightening is probably the most promising solution now available, it is of course only a stopgap measure. It would buy us time at a moment when time is the most important factor, but it would not remove carbon from the atmosphere, which really has to be done.

4. Arithmetic Includes Both Addition and Subtraction

Finally, there is a fourth flaw in expecting the total of individual emissions to predict the earth’s temperature: The model based on individual carbon footprints only adds, never subtracts emissions. What a crazy kind of arithmetic that would be! But the questionnaire on my iPad assumed that I add carbon every day to the atmosphere without ever removing any.

Now it is true that, unless you’re a farmer or a forester, you probably do not remove much carbon from the atmosphere. Plants do it perfectly, but not individual persons. Still, there are ways for enterprises and governments to subtract from the total. Therefore, any good predictive model certainly must use arithmetic that involves, not only addition, but also subtraction.

But I don’t think this flaw in the hypothetical model is just a fluke. Indeed, it is part of the prevailing ideology. You are regularly told that it’s impossible to subtract much ambient carbon, and that you should forget about it!

Admittedly, this ideology is almost justifiable. Carbon is killing us, but millions of people still deny that or refuse to change their behavior. We have to convince them.

But deniers offer every plausible excuse for continuing their polluting habits, and often resort to a loophole called “offsets.” Indeed, not only do climate-change-deniers buy offsets, but also many citizens who are trying extra-hard to be responsible. I used to buy tree-planting offsets whenever I flew, but now I just stay at home, which is better for the world. Still, not everyone can completely avoid travel.

Offsets resemble “credits” in the cap-and-trade system of pricing carbon emissions. In such a scheme, every country and business is allowed a “cap”—a limiting maximum—of greenhouse gas to emit. A country or business that emits less than their cap is given credits (one credit being equal to one tonne of CO2-equivalent emissions saved) which it can sell to other organizations that expect to exceed their cap. Cap-and-trade is a reasonable way of charging for emissions, but less efficient than simply charging a fee or tax on every purchase of polluting energy.

An “offset” is a similar purchase made voluntarily by a company or person to compensate the rest of us for continuing to pollute with emissions. For example, the ride-sharing company Lyft claims to be “carbon neutral” because it buys offsets to compensate for the CO2 it emits. Most of these offsets fund tree-planting projects or solar farms in poorer countries.

While offsets create an opportunity for commendable behavior, they are morally ambiguous, for they can also provide easy justifications for wrongdoing. Indeed, James Hansen compares offsets to the corruption that prompted the Protestant Reformation:

“Offsets are like the indulgences that were sold by the church in the Middle Ages. People of means loved indulgences, because they could practice any hanky-panky or worse, then simply purchase an indulgence to avoid punishment for their sins. Bishops loved them too, because they brought in lots of moola.”

Anything that subtracts carbon or heat from the atmosphere could be sold as an offset, and that fact creates a “moral hazard.” Forestry is an obvious example. Trees suck carbon out of the air and keep it locked up until they are burned or rot. And anyone who wants to keep flying in planes may feel better if she pays to have trees planted somewhere on earth, to “cancel out” her plane emissions. But in reality, there’s already more carbon in the air than can be removed by another trillion trees. We have to stop flying and also plant trees.

Yet some people cling to the delusion that technology will soon save us with a new magical gadget that captures and buries all the excess carbon we pour into the air—and therefore we can keep pouring it out. You and I have to fight that assumption, and many environmentalists fight it by denying that it’s possible to subtract enough carbon to be worth attempting.

But that is a lie, and it is costing us precious time. There are probably hundreds of ways to subtract carbon from the atmosphere, but nobody has tried to list them or figure out which are the best ones to bet on. We absolutely need such a list, and we urgently need research to help prioritize these methods wisely. So, I have made a first attempt to pick twelve of the most promising methods, and will list them in the remainder of this article. Measures that subtract carbon are called “Negative Emission Technologies” (NETs). The future of humankind depends on using the best ones—maybe all of them—and soon!

A Dozen Ways to Subtract Carbon’s Heat

Warning: There are plenty of possibilities for subtracting carbon from the ambient atmosphere—but we’re in a bind. It’s too late to be cautious, for we need research that takes time and we have no time left. We have to take chances now, and there may be risks that won’t be mentioned in this brief list. Each option has both advantages and disadvantages, and many decisions in this emergency will be dicey. I’m sorry. Now, here are twelve potential ways to help save each other.

1. Trees can Subtract Carbon’s Heat

Thank heavens for chlorophyll! With that green stuff, photosynthesis achieves what you and I cannot do: capture carbon dioxide and turn it into sugar and oxygen for people to breathe. Fortunately, we can grow lots of plants to perform this helpful service—or at least we can stop destroying the ones that do the best job of it: big, old trees. About half of a tree’s dry weight consists of carbon, so the larger the tree, the more carbon it’s holding. And as long as it lives, it retains that carbon in its trunk, branches, and roots.

However, human beings keep destroying more forests each year than we plant. In 2020, more than ten million acres of tropical forest were lost, releasing as much carbon to the air as 570 million cars emit each year! Tropical deforestation is the source of eight percent of global carbon emissions.3 Deforestation is slowing but nevertheless, global forest area decreased between 1990 and 2020 by an area about the size of Libya. If we want to subtract carbon, we have to save existing forests and plant new ones.

There are three trillion trees on the planet now,4 and according to the Crowther Lab, a research organization in Switzerland, there is room for about one trillion more.5 Such an increase would mean that, when the trees are mature, they would sequester up to 200 gigatonnes more carbon than now. In their initial paper, the researchers estimate this as equal to 25% of the carbon now in the atmosphere. However, after their estimate was criticized, they reduced it substantially and warned that afforestation can actually be detrimental if an inappropriate combination of species are chosen or planted in unsuitable soil. Moreover, even in favorable conditions, the mortality rate of young trees is very high. Of three or four trees, only one typically survives. It is far smarter to protect mature trees than to cut them down and plant new ones.

The Crowther Lab prepared a world map showing the sites where the trillion trees might be added. They did not exactly recommend planting in those places, but a reader might infer that they meant it as a plan. I was skeptical about their map for two reasons. First, they showed the Arctic as the site for many of those additional trees—but that idea contradicts other findings: that trees in boreal forests actually have an overall warming effect, unlike trees in tropical zones, which cool the planet.6 As ecologist Ken Caldeira explains,

“Trees perform three major climate functions: They absorb carbon, which they pull from the atmosphere, creating a cooling effect; their dark green leaves absorb light from the sun, heating Earth’s surface; and they draw water from the soil, which evaporates into the atmosphere, creating low clouds that reflect the sun’s hot rays…which leads to cooling. These three factors… taken together create very different results in [different] latitudes…”7

The main factor is whether the land is covered in snow during winter. Trees have a warming effect in snowy areas because they are dark and absorb light and because evaporation there is less efficient, so there are fewer clouds to block the sunshine.8

About 24 percent of the land in the Northern Hemisphere has permafrost under it. As it thaws under the warming influence of trees, immense amounts of prehistoric vegetation also thaws and rots, emitting vast quantities of methane, which warms the climate far more than carbon dioxide. Thus, there are actually reasons to prevent the encroachment of forests in the Arctic, rather than encouraging it, as the Crowther Report seems to do. Unfortunately, there has been too little research to be sure, though the issue is crucial to humanity’s future.

Here’s my second objection to the Crowther map showing sites for the new trillion trees: It specifically excludes land already in use by towns and agriculture, so any new forests would necessarily be remote. Do they expect helicopters to ferry saplings and people to mountains every weekend, to weed and water the trees for two or three years? Not likely! Okay, maybe they can use drones to shoot seeds into the soil in remote areas, but the tree mortality rate will be high. And remember: A trillion equals a thousand billion, whereas even Canada has promised only to plant two billion. For a trillion trees to survive, people will have to care for them, and people live on farms and in towns. We can only plant close to home.

Agriculture and cities are not the enemies of forestry. Most crops can be surrounded by trees or hedges, and many crops and farm animals thrive in shady pastures. We can plant trees along every country road and most city streets. You can replace your lawn with a small forest, which will not require pesticides, CO2-polluting lawn mowers, or even sprinklers after the first three years. (Watch my talk shows number 53 and 80 about Miyawaki forests and then plant about four different local species per square meter. Thanks!)

Here’s the best news: Within 12 years you will no longer want to own a car. Driverless electric taxis will be far cheaper. The streets will be full of vehicles, but there will be few parked cars, since taxis will just drive on instead of parking. We can plant trees in all those parking spaces along the street and fill downtown parking lots with forests. Then you’ll get your exercise by tending the urban forests on weekends for the first three years, after which they’ll take care of themselves. Let’s aim for a trillion!

2. Biochar can Subtract Carbon’s Heat

Charcoal is made by burning wood or other carbon-containing wastes in the absence of oxygen. Biochar is a synonym for charcoal. In South America there are areas of rich, black soil ten feet deep where Indians buried biochar 7000 years ago. That charcoal still retains the sequestered carbon. We too could make biochar from wood or other waste and bury it, subtracting huge amounts of carbon from the atmosphere and, in most cases, greatly improving our soil (which is degrading rapidly) and the nutritional quality of our food.

If you drive through the Rocky Mountains, you’ll see hundreds of miles of red forests where the trees have been killed by pine beetles. Most of them will probably rot and release all their carbon to the atmosphere, but I have a better idea. Canada and the US governments should cut them down, put them in trenches, cover them with soil to keep the oxygen out, and burn them, making biochar and leaving it right there in the ground. That will sequester a gazillion tonnes of carbon. (Is a gazillion the amount that the tar sands are emitting now?) Better yet, sell the biochar to farmers so they can enrich their fields. Unfortunately, few farmers have ever heard of biochar, so there is no market for it. We can create a market, however, with a new law requiring that all new fertilizers must contain, say, ten percent biochar.9

3. Soil can Subtract Carbon’s Heat

Dirt can hold a lot of carbon, and the best soil is full of it. Nevertheless, more than 75 percent of Earth’s land is substantially degraded, to the detriment of 3.2 billion people. Within thirty years, 95 percent of the Earth’s land areas may be degraded, forcing hundreds of millions of people to migrate because of food shortages.10

Fortunately, there are known ways of avoiding land degradation and many farmers are adopting them—though maybe not quickly enough to prevent disaster. I have been interviewing numerous experts on regenerative agriculture for my talk show, and it is apparent that these techniques are no longer controversial; it’s just a matter of time for them to catch on, worldwide.

“Regenerative” farming tries to restore the quality of the soil. These farmers avoid using chemical pesticides and chemical fertilizers, which impede the ability of the plants to absorb nutrients and worsen the climate crisis. They like to rotate their crops, planting a different one each season, and particularly favoring legumes, which fix nitrogen. They use composts, mulches, and cover crops to promote biodiversity—not with the intent of harvesting them, but to protect the soil, which should never be left bare or exposed to the elements. They avoid plowing or turning the soil over, which releases precious carbon to weather erosion.

Animals can either ruin soils by overgrazing or, if they are managed well, restore the fertility and carbon content of soil that had turned into a desert. “Regenerative grazing,” or “holistic management” is a method Allan Savory developed after witnessing Africa’s savannah degrade over time. Previously, animals grazed on tall grass in tight herds, for predators could only attack the animals on the outer edges of the herd. They moved together, loosening up the top layers of soil as they grazed, and fertilizing it with their urine and dung. After a few days, the herd would move on to the next pasture, letting this one “rest” several months before they’d return. The “rest” matter.

In contrast, conventional cattle and dairy farmers treat livestock in a very different way. Cows are scattered widely apart over the pasture, and they typically stay there all the time, regardless of the effects they have on the soil. But Savory is teaching farmers to observe their herds and the soil closely and move them to another paddock when they’ve eaten, trampled, and fertilized the current one just the right amount. Regenerative ranchers now keep their herds together within electric fences, which they move to enclose the next paddock.

This works. On the internet you can compare before-and-after photos of land that has been restored to fertility by holistic management. When it rains, the water does not flow off in gullies but is absorbed and retained.

There are now techniques for measuring the carbon content of soil and the emissions from animals. Belching ruminants are one of the main sources of methane in the atmosphere, so many of my friends have become vegans for the sake of the climate. Regenerative farmers, however, oppose that and provide evidence that they can sequester more carbon than cows emit. For example, a regenerative farm in Georgia, White Oak Pastures, raises cattle, sheep, goats, hogs, poultry, and rabbits using the same methods that their owner’s great-grandfather used. Carbon measuring tools substantiate their claim: “We store more carbon in the soil than our cows emit during their lives.”11

Now dairy farmers can also subtract methane from the atmosphere. Dairy cows and cattle destined for slaughter usually spend their final months fattening up on grain in “feedlots” instead of grazing in pastures. Of course, they belch and fart there too, still adding methane to the atmosphere while no longer contributing manure to compensate the soil. But now farmers can collect these wastes in “lagoons” covered by plastic tarps that capture the methane, which they sell as fuel. They sell the manure residue for use as organic fertilizer,12 though I don’t know whether, so far, their milk and meat products actually are “net carbon negative.” Perhaps so, if they also subtract methane emissions by feeding the cows seaweed.13

4. Wetlands Can Subtract Carbon’s Heat

Wetland plants absorb carbon dioxide and when they die, that carbon doesn’t get released back into the atmosphere but accumulates at the bottom of wetlands. This subtracted carbon is kept stored as peat for thousands of years. When peatlands are drained for agriculture, forestry, or peat harvesting, carbon and nitrogen are released as carbon dioxide and nitrous oxide. About 25% of the world’s peatlands are in Canada. So long as they are not drained, they keep subtracting more carbon every year.14

5. Bioenergy with Carbon Capture (BECCS) Can Subtract Carbon’s Heat

Biomass is organic matter used as a fuel. When agricultural residue or forestry waste, for example, is processed, its CO2 can be captured, placed in geological storage sites and thereby subtracted from the atmosphere. Sometimes the CO2 is not stored but converted into biofuels such as ethanol, which is carbon-negative, subtracting even more from the planet’s temperature. Unfortunately, most BECCS technologies are unsustainable, for they use biomass from land that might better be used for producing food.

6. Engineered Wood Can Subtract Carbon’s Heat

Trees that have died from warming or that need to be thinned to enhance forest health and prevent fire can be engineered into products that replace carbon-intensive building products such as cement and steel. “Mass timber” ­ slabs of wood held together with adhesives—is used now for constructing tall apartment buildings, which subtracts from the atmosphere the carbon emitted by conventional construction.

7. Burning Methane Can Subtract Carbon’s Heat

Currently the most ominous threat to humankind is probably the methane in permafrost and shallow areas of the Arctic Ocean. About 1,500 billion tonnes of carbon lie frozen and compressed there—twice as much as in the atmosphere—and it is warming and escaping. Clouds of white gas emerge, which burn if ignited. Huge methane reservoirs could gush out explosively, raising the global temperature immediately and irreversibly by a degree or two. One solution is to burn as much of it as possible. Burning converts methane to CO2—certainly not a gas we’d welcome, but far better than the methane, which traps heat in the atmosphere 86 times more effectively than CO2 on a 20 year time horizon. But at present there seems to be no way to burn a significant part of those methane plumes, let alone prevent massive explosions. Let me know if you hear of a way.

8. Iron Salt Aerosol Can Subtract Carbon’s Heat

In the short term, methane is a far more powerful greenhouse gas than CO2, but it does not remain in the atmosphere for a thousand years, as CO2 does, but within a decade or two is usually oxidized, to become CO2. This process occurs in nature when methane contacts (a) the hydroxyl radical HO° or (b) chlorine atoms. Iron salt aerosol can enhance both of these processes. The most promising solution to our methane problem is to bring iron into contact with sea-salt (sodium chloride), thereby generating chlorine atoms, which in turn oxidize the methane.

For you chemists, here are some details: Sodium Chloride from natural sea salt spray naturally generates hydrogen chloride (hydrochloric acid) when it encounters natural or pollution-related acidity. Hydrogen chloride reacts with soluble iron hydroxides to form Iron Salt Aerosol: iron chloride (FeCl3) Under sunlight, iron chloride generates chlorine atoms (Cl), which oxidize methane (CH4). Voila!

And this goes on in nature all the time. For example, African sandstorms carry iron across the Atlantic toward the Amazon rainforest. Eventually the iron falls, feeding the ocean’s phytoplankton or fertilizing the rainforest, and destroying evil methane along the way, whenever it contacts sea salt spray.
Scientists want to apply those principles by spraying iron particles above the ocean. If done massively, that will subtract a lot of methane. Watch my talk show15 246, which explains this:

9. Accelerated Rock Weathering Can Subtract Carbon’s Heat

For millions of years, nature has been slowly eroding rocks and subtracting atmospheric CO2. For this it uses rain, which is a bit acidic from absorbing CO2 in the air. The rain breaks down the rocks into grains and bicarbonate, which flows into the ocean and remains either dissolved or locked up on the ocean floor.

We can copy nature’s plan by pulverizing volcanic rocks (faster than nature does) and sprinkling the powder on farm soil, where it absorbs CO2 and where plants and microbes can speed up the process and make the minerals into nutrients that regenerate degraded soil.

A variant technology spreads olivine (the second-most abundant rock on earth), as powder on beaches, where the ocean waves will continually stir and dissolve it. Such a project would combine this weathering method with number 10, shown below.

10. Ocean Alkalinity Enhancement Can Subtract Carbon’s Heat

This technology is the twin of number 9, described above: Enhanced Weathering, which sprinkles the crushed minerals on land. Both methods subtract CO2, but the olivine or other crushed stone, when added to the ocean, also counteracts the increased acidification.16 Sea water used to have a pH of 8.1, but it is now down to 7.9, possibly close to a saturation limit. The cause of acidification is the same as the cause of global warming: the emission of carbon dioxide, mainly from fossil fuels.

Enhancing alkalinity will mostly be done by sprinkling mineral powders from ships. This is going to be necessary, but there may be unforeseen risks.17 The practicality of the project will largely depend on such factors as the proximity of the mining and crushing operations to the sites for dispersing it, to minimize transportation costs. The managers of the most advanced experiment, Vesta, claim they can subtract far more CO2 than their project will generate. They are the people who plan to turn beaches green with crushed olivine.

11. Direct Air Capture Can Subtract Carbon’s Heat

Suppose you could put up some big fans to blow air through a filter and collect the CO2, then store it underground. Actually, that’s possible. Two organizations are already doing so: Climeworks, based in Switzerland and Iceland, and Carbon Engineering, based in Squamish, B.C. and expanding into Texas. Each year the BC plant removes one million tons of carbon dioxide from the atmosphere, which is equivalent to the work done by 40 million trees. It does not sequester the carbon underground, as Climeworks does in Iceland, but makes it into a carbon-neutral fuel—which is economically realistic. United Airlines is funding Carbon Engineering’s planned operation in Texas and expects it to subtract a million tons of CO2 each year, beginning in 2025 or later.

However, no one calls this technology cheap or efficient. Scientific American compared the cost effectiveness of several methods for subtracting carbon and found Direct Air Capture about four times as costly as the other methods. Maybe let’s wait for some improvements.18

12. Carbon Dioxide, Bound to Durable Carbon, Can Subtract Carbon’s Heat

What if, instead of burying the captured CO2, we could sell it? Good idea—but who would buy it and how would they use it? Let’s be clear: We won’t ever use all the CO2 that could be captured; the emissions from fossil fuels simply dwarf all potential markets for it. On the other hand, carbon dioxide already is a commodity used by a range of industries. If it can be captured efficiently by one of the methods I’ve listed above, it will be possible to lock up a significant amount in durable, useful products.

Concrete is the best example. It is the second-most used substance in the world, after water,19 and is the source of up to eight percent of our carbon emissions. Fortunately, it can be recycled—crushed and reused as aggregate in new projects. However, the global warming problem results from superheating limestone to make the Portland cement binder. Now, however, a technology is developing that dissolves captured CO2 to form a carbonate, which can be combined with waste concrete to form a synthetic limestone. This actually subtracts CO2 from the air and makes it into a durable, carbon-negative concrete—a permanent carbon storage material. Hooray!


The twelve innovations that I’ve listed here are only a few of the opportunities before us. None of them, nor probably all of them together, can eliminate the huge challenge we face in cutting carbon emission down to “net zero.” On the other hand, net zero will not save us, even if we could reach it today. Our globe will keep on heating unless we subtract carbon from the atmosphere, so we must do both: less adding, and more subtracting. Good luck! We’ll need it.

1 “What if Technology Tracked All Carbon Emissions?” The Economist, 2 July, 2020.

2 Ralph Charni, Thomas Cosimano, Connel Fullenkamp, and Sena Oztosun, “Nature’s Solution to Climate Change,” Finance and Development, Dec. 2019, Vol. 56, No. 4.

3 Dong-Kwan Kim, “Afforestation can help to tackle climate change. Here’s how,” World Economic Forum, Nov. 3, 2021.

4 Rachel Ehrenberg, “Global Forest Survey Finds Trillions of Trees,¸” Nature,  Nature (2015).

5 Jean-Francois Bastin, Yelena Finegold, Claude Garcia, Danilo Mollicone, Thomas W. Crowther, “The Global Tre Restoration Potential,” Science July 5, 2019, Vol. 365, Isssue 6448.

6 Nikhil Swaminathan, “More Trees, Less Global Warming, Right? — Not Exactly” Scientific American, April 10, 2007.

7 Ibid.

8 Ibid.

9 See my talk show interview with Professor Johannes Lehmann. . Also, Johannes Lehmann and Stephen Joseph, Biochar for Environmental Management: Science, Technology and Implementation, 2nd edition, March 2021.

10 Stephen Leahy, “75% of Earth’s Land Areas Are Degraded.” National Geographic, March 26, 2018.

11 White Oaks Farm website:

12 Professor Frank Mitloehner in my talk show with him, “Cows.”

13 Ibid.

14 Emily Jerome, “Five Reasons to Love Canadian Wetlands,” National Environmental Treasure.

15 Renaud de Richter, Franz Dietrich Oeste, Tingzhen Ming, Sylvain Caillol, Robert Tulip, John MacDonald, Clive Elsworth, “Iron Salt Aerosol a natural method to remove methane & other greenhouse gases,”

16 James Temple, “How green sand could capture billions of tons of carbon dioxide” MIT Technology Review, June 22, 2020.

17 K. M. Krumhardt, N.S, Lovenduski, M.C Long, M. Levy, K Lindsay, J. K. Moore, C. NHissen, “Coccolithophore Growth and “Calcification in an Acidified Ocean: Insights From Community Earth System Model Simulations,” Journal of Advances in Modeling Earth Systems, March 12, 2019, . See also

18 “The Direct-Air Capture Debate,” Anthropocene Magazine, March 25, 2021.

19 Colin R. Gagg, “Cement and concrete as an engineering material: An historic appraisal and case study analysis”. Engineering Failure Analysis, 1 May 2014.

Peace Magazine January-March 2022

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