Yes, I’m joking with this title – but not entirely! For about three years I’ve been advocating for large technological solutions to the climate crisis. True, the reduction of greenhouse gas emissions is the key solution to the crisis, but that turns out to be extremely hard to achieve. Indeed, carbon emissions are still increasing every year globally. We must quickly do more to save the world. So, I want to convince you here that the most feasible way of reducing global warming is by making a lot of concrete.
It’s a lot easier to reduce emissions if you capture the concentrated CO2 at the source – such as inside the smokestack – before it diffuses into the air. But even if you do so, what then can you do with what you’ve captured?
You might make some of it into soft drinks, or bury it, or pump it into depleted wells to force the remaining oil out. Some geoengineers make it into fuel, but there’s no real market for it. It can be purified and made into a liquid, but that takes a huge amount of energy. So, there is hardly any practical use for large amounts of carbon dioxide. Except one: You can make it into concrete! Well, at least one company can do that. So far, it’s the only one I’ve found.
The company is called Blue Planet. It captures CO2 from industrial flues before it is emitted and, without purifying or concentrating it at all, prepares it to be locked up permanently in concrete structures. Moreover, here’s the amazing truth: Unlike ordinary concrete, Blue Planet’s product is actually carbon-negative! The more of Blue Planet’s concrete you pour, the more carbon you keep out of the atmosphere and the more you cool the climate.
This fact is astounding, for ordinary concrete is one of the leading causes of global warming! It’s the source of about 8 percent of the world’s CO2 emissions every year. Yet, Blue Planet’s website boldly asserts that “half of all anthropogenic CO2 can be captured and permanently stored” using their mineralization technology.
To find out how the company achieves this, I called them in Silicon Valley about three years ago for an interview with their friendly inventor and head, Brent Constantz. Together we made two of Project Save the World’s video forums. Here’s what I learned.
All concrete is made of four things:- Cement (10-15% – acts as a glue and is a huge source of CO2 in the atmosphere).
- Aggregate (60-75% – rocks and sand that contain carbon and that make up concrete, are carbon sinks).
- Water (14-20%).
- Air (1-8%).
MAKING PORTLAND CEMENT
First, let’s consider cement, the source of greenhouse gas emissions. Ordinary Portland cement is made by heating a mixture of limestone and clay to 2,700°F in kilns powered by fossil fuels. This converts the limestone to lime, releasing CO2 in the process. The leftover nodules, known as clinker, are ground up to form Portland cement. But the process means that every tonne of cement is producing an estimated 622kg of CO2 that warms our planet. In 2022, there were 4.4 billion tonnes of it produced and every year the amount increases.
Although cement constitutes less than 15 percent of the concrete, the production of that cement is the source of global CO2 emissions. Eliminate those emissions and you’ll have carbon-neutral concrete – which alone would be a big step toward solving our crisis.
So, if you search Google, you can find numerous companies that are trying to produce “low carbon concrete” – almost always by manufacturing cement that emits less CO2. That’s a sensible goal but, so far, the results have been underwhelming. Moreover, for safety reasons, experimental recipes for cement are required to undergo decades of testing before they can be approved for use. We need a solution today.
Brent Constantz began his career as an expert on cement; he invented cements that are still in hospital operating rooms for gluing broken bones back together. Nevertheless, he wisely abandoned the quest for better cement and turned to the other side of the equation — improving the aggregate component of concrete, which sequesters carbon.
LIMESTONE AGGREGATE – QUARRIED OR SYNTHETIC?
The most common form of aggregate is crushed limestone from quarries. Limestone is calcium carbonate – the main form in which Mother Nature keeps her carbon stored out of contact with the atmosphere. Immense amounts of carbon are locked up in rocks. Anything ‘mega’ refers to the number of millions. Anything ‘giga’ refers to the number of billions. And, as Brent Constantz explained:
“There’s about 830 Gigatons of carbon in the whole atmosphere. There’s about 2400 Gigatons of carbon in the entire biosphere – all the rain forests, plankton in the oceans. There’s about 38,000 Gigatons of carbon in the hydrosphere – the oceans, lakes, rivers, ice caps. But there’s about 100 million Gigatons of carbon in the lithosphere, mostly in the form of limestone… Most of Earth’s carbon is sitting in the lithosphere in a mineralized state.”
Suppose we could capture a lot of that, turn it into limestone, and use that limestone as the aggregate for buildings, sidewalks, and airports? We could just ignore the emissions from making the cement, which, though a huge amount, would be dwarfed by the staggering amount of carbon we’ve locked away in our synthetic limestone aggregate.
Can that be done? Yes. Blue Planet has been doing so for several years.For example, one San Francisco air terminal is made of its concrete. According to their website, blueplanetsystems.com, “Our process can use dilute CO2 from any source, at any concentration, and turn it into valuable building materials to enable carbon capture at a profit. Each tonne of our aggregate permanently mineralizes 440 kg of CO2, preventing it from ever leaking or accumulating in the atmosphere.”
HOW BLUE PLANET DOES IT
The process starts by capturing CO2 from industrial flue gas streams. These are exhaust gases from power plants, cement kilns, or other industrial facilities. The flue gas is bubbled through a water-ammonia solution and the CO2 reacts to form carbonic acid (H2CO3), which then dissociates into bicarbonate (HCO3) and carbonate (CO3²-) ions. This capture process can achieve high CO2 removal rates, often exceeding 90 percent.
The next step is the heart of the process: mineralization. The captured CO2 (in the form of carbonate and bicarbonate ions) is reacted with a source of calcium ions. This calcium can come from industrial by-products such as demolished concrete, cement kiln dust, steel slag, fly ash, or magnesium silicate. The remarkable product of this mineralization process is calcium carbonate (CaCO3), the same mineral as limestone. In about half a second, it precipitates out of the solution as solid particles which permanently sequester the CO2 in a stable solid mineral that can be used as aggregate for concrete.
This process mimics the natural mineralization by a lobster that has shed its shell and somehow creates a new one within a few hours.
Here is a photo from Blue Planet’s website showing some of the new synthetic limestone pebbles, now aggregate.
After the calcium is removed from the old waste concrete, there is bare rock and sand left over, which can be returned to the market to be re-used for other purposes. This approach not only provides the necessary calcium for the new limestone but also helps recycle old waste materials, reducing the need for new mining. The demand for limestone greatly exceeds the amount available near to cities, so usually it is now transported 200 miles or more from the quarry. One advantage to using demolished concrete instead of quarried rock is that, instead of having to pay a high price, Blue Planet gets paid for removing the waste concrete from its original location.
SHOW ME THE NUMBERS!
Blue Planet’s website makes the extraordinary claim that, “30 billion tons of concrete are used each year; 8 percent of global CO2 emissions are from concrete production; 20 billion tons of CO2 per year can be removed using our aggregate.” Actually, such numbers can only be “guesstimates,” and I wanted to check theirs against another credible source, so I asked Chat GPT4 to determine whether there is any plausible way that concrete could actually be carbon negative. Here’s the estimate by AI, which is somewhat lower than Blue planet’s, but still stupendous.
“Each tonne of Blue Planet aggregate can mineralize up to 440 kg of CO2, effectively sequestering this amount of carbon dioxide from the atmosphere. In contrast, the production of conventional concrete emits approximately 100–200 kg of CO2 per tonne. Therefore, using Blue Planet concrete can result in a net reduction of about 240– 540 kg of CO2 per tonne compared to traditional concrete. If all the concrete poured worldwide in a year were made from Blue Planet concrete, the potential CO2 emissions reduction would be substantial. Given that over 10 billion tonnes of concrete are used annually, this could lead to a reduction of approximately 2.4 to 5.4 billion tonnes of CO2 emissions per year. (i.e. 4 – 10 percent of the 53.4 billion tonnes expected for 2024.)
But there’s quite a disparity in these estimates: Blue Planet says “over 30” gigatons are produced annually but GPT4 estimates only “over 10 billion tonnes.” Who’s more accurate?
I asked Gemini, another AI system. Gemini prefers to estimate the amount in cubic meters (14 billion cubic meters in 2023) because the density of concrete varies so much. But when I pressed for it to estimate in gigatonnes, it made some assumptions about the average density and replied, “based on our assumptions, approximately 33.6 gigatonnes of concrete are produced globally each year.“ (“Tons” and “tonnes” – or “metric tons” are not very different units of weight: 2,000 pounds and 2204.5 pounds respectively.) Anyway, Blue Planet’s estimate is closer to Gemini’s than to GPT4’s – and GPT4’s was already stupendous. It said that Blue Planet could theoretically permanently subtract between 4 and 10 percent of global CO2 emissions per year. Of course, we cannot actually expect all – or even half – of the world’s concrete manufacturers to adopt the Blue Planet system. Thousands of factories exist all over the world that cannot be remodeled.
However, the possibility is now becoming recognized that concrete can be carbon-negative. When I first interviewed Brent Constantz in 2022, he said that his company has investments from Mitsubishi in Japan and and discussions with China, where it would be feasible to build many plants. A friend of mine in Italy mentioned that his university is using Blue Planet concrete in new construction. I live in Canada, where Lafarge-Holcim has a contract now to build many Blue Planet factories. Chevron is now also a partner.
One of Project Save the World’s friends, Peter Fiekowsky, visited Blue Planet’s first plant in Los Gatos, California and shared some of his photos with us in a forum: https://tosavetheworld.ca/episode-512- lock-up-carbon-in-concrete. Below is his photo of the pipe carrying CO2 from the natural gas power plant across the street.
THE MARKET FOR CONCRETE
Concrete is the most common building material in the world, unless you count water. Imagine a cube of concrete about 4 feet on each side – that’s how much is produced for every single person each year! About 30% of all the material extracted and used each year (including mining, oil drilling, agriculture, etc.) goes towards making concrete.
The amount of concrete produced exceeds the weight of all the biomass we use annually. It also surpasses the weight of all the fossil fuels we use annually. In the time it takes you to read this sentence, the equivalent of an Olympic-sized swimming pool of concrete will have been poured somewhere in the world.
Concrete and its ingredients are heavy substances, so transportation costs are the crucial economic factor determining where a plant can be profitably located. The ideal location for a plant is close to an industrial smokestake source of CO2, as well as to the location of demolished concrete or other calcium source, and to the location where the concrete will be poured.
Measured by the total global amount of concrete, Blue Planet is still a tiny company. In a series of forums in 2023, I interviewed a number of experts on concrete – mainly university professors of civil engineering – and almost none of them had even heard of Blue Planet yet. They were still talking about how they hoped to produce “low carbon” concrete so as to reduce its huge carbon footprint by a few percent.
GOVERNMENT AS CUSTOMER
About 40 percent of all concrete is purchased and used by governments for public structures. How much impact would we have on global warming if we convinced all our governments to purchase only carbon-negative concrete? (I won’t guess, but you can work out an estimate for yourself.)
Of course, governments cannot currently purchase only carbon-negative concrete, but governments can inventivize companies to change very quickly. And that fact gives citizens some leverage.
At present, governments have regulations and standards for the materials that they purchase for their countries’ infrastructure. Canada already specifies that its projects should use “low-carbon concrete,” so the manufacturers invariably meet those standards. However, there is no particular incentive for companies to innovate beyond meeting those standards. But governments can have a larger impact. I interviewed Robert Cumming, an executive in the huge concrete manufacturing company Lafarge. He said their factories across Canada now are searching for ways to reduce carbon emissions. They see Blue Planet as especially promising and are adopting it, though he cautioned me that “there’s going to be a price to switching from a very old, proven commodity. While we’re transitioning, there’s going to be a more expensive economy.”
Cumming suggested that governments can incentivize these investments by announcing that they will always purchase whatever available concrete has the lowest possible CO2 emissions. Companies invariably react immediately to such changes in the way that they must compete for contracts. So, that gives us citizens and NGOs an extra means of helping to reduce global warming. We can lobby politicians to incentivize rapid innovation in the concrete industry. With millions of immigrants arriving, we’ll need more schools, highways, sewers, and airports. These can be made from carbon-negative concrete.
Although Brent Constantz is an affable man, when I interviewed him he seemed reluctant for me to publicize his company. He said that environmentalists get excited and call up, wanting to buy some of his concrete – even if they live in Florida, though his plant is in California. It makes no sense to ship concrete far.
So, please don’t pester Constantz. Instead, spend your time pestering your government to incentivize the construction of factories producing carbon-negative concrete as fast as possible.