Concrete ways to solve our concrete problem

Folkhem/Arvet Ulrika Nihlén

Concrete production is one of the most carbon-intensive industries in the world — and it’s booming. In the next forty years the world is going to build a New York City every month.

The good news: Alternatives are booming as well, and the world’s first carbon positive apartment buildings have already been erected.

While the climate debate in recent years has had a lot of focus on airplanes, big oil and plastics, the concrete industry has more or less managed to stay under the radar. This might seem a bit strange, considering that concrete is the second most consumed product on the planet after water, and one of the leading emitters of greenhouse gases, beaten only by the iron and steel industry.

The key ingredient in concrete is cement, and to make cement you have to heat limestone and other ingredients to 1 450 degrees C (2 640 degrees F) by burning fossil fuels. Roughly one ton of CO2 is emitted per one ton of cement produced, and in recent decades the production expansion has gone bananas. China recently used up more concrete in three years than the United States did in the entire twentieth century, and the curve keeps pointing upwards. If cement was a country, it would be the third largest emitter of carbon dioxide in the world, after China and the US.

If we continue on this path, we can forget about the goals of the Paris agreement. But luckily enough, we don’t have to. New innovations are popping up around the globe, and many of them are determined to capture carbon in the material and lock it up for good.

Brent Constantz, CEO of Blue Planet in California, is a Silicon Valley entrepreneur and inventor of more than 100 issued patents — and a 100 more currently pending. He is also a consulting associate professor at Stanford University, where he teaches bio mineralization. It was the knowledge in that field that led to the idea on how to store Co2 in concrete.

”There are a number of ways to capture CO2, but the question is: What do you do it once you’ve captured it? What we’re doing, which is revolutionary, is we’re turning the CO2 into synthetic limestone, by using a process very similar to what happens in oceans when corals grow. Each ton of CO2-sequestered limestone traps 440 kilograms of carbon dioxide, preventing it from ever reaching the atmosphere again. Even if you tear down the building, the carbon’s still in the limestone”, Brent Constantz says.

This, according to Blue Planet, makes the whole concrete production process carbon negative. The other huge benefit of the technique is that it takes limestone mining out of the equation.

”About 70 percent of all rock used in concrete is limestone. There is about 50 billion tons of rock that is mined every year and transported for use in concrete, asphalt and road base, and it’s growing at about 8 percent a year. Our approach would save enormous transportation costs and carbon footprint”, says Brent Constantz.

Blue Planet’s product was recently used in the construction of a boarding area in San Francisco Airport, and the test results showed that the material met all necessary specifications. A Life Cycle Assessment (LCA), conducted by a team from Stanford University, also concluded that Blue Planet´s product could reduce CO2 emissions by up to 48 percent compared to the use of conventional aggregate.

Another California company, Calera, uses CO2 from smokestacks to make Calcium Carbonate, which can be used to replace a portion of standard Portland cement in construction. In Canada, the company CarbonCure injects captured CO2 in concrete as it’s being mixed, to make the material both greener and stronger, and the innovative technology is now used by to hundreds of concrete producers across North America and Southeast Asia.

Interesting carbon capture techniques are also being developed at various universities.

Chemists at the Technological University of Munich have developed a process to make carbon fibres from algae. Algae convert CO2 from the atmosphere or power plant exhausts into algae oil, which could then be used to produce carbon fibres at a low cost. Thanks to their strength, less cement needs to be used in the construction process. And steel might not be needed at all, since granite reinforced with carbon fibre could produce beams with the same load-bearing capacity, while being lightweight as aluminium.

At the University of California a carbon upcycling team has found a way to convert CO2 into a building material called CO2NCRETE, which has the similar strength and functionality as traditional concrete, but with up to 70 percent less climate impact.

Then there are those who take things a bit further, by skipping the concrete issue completely. Six years ago in Sweden, a pioneer apartment building named Strandparken was constructed in Sundbyberg, next door to the capital Stockholm. It was at the time the largest wooden building in the world. The girders, the beams, the inner walls, the balconies, the facing — all was made of wood. No concrete. No steel. No reinforcing iron bars.

Folkhem/Arvet Petra Bindel

Sandra Frank, markering director at Folkhem, the construction company behind the project, is still passionate when she talks to WeDontHaveTime about the project.

”Wood is the only renewable construction material that we have. Strandparken consists of 1 200 cubic metres of wood. In Sweden, this is regrown in less than a minute”, she says.

A study made by the Swedish Wood Building Council showed that the climate footprint for Strandparken was one of the lowest ever recorded for an apartment building.

”In the climate debate there is a lot of talk about carbon capture at the moment, often in terms of advanced technological solutions that doesn’t even exist or have been tested on a large scale. But building with wood is carbon capture too”, Sandra Falk says.

Even though Strandparken was a pioneer project, which always adds a lot of extra costs, the building turned out to be only about 20 percent more expensive than a standard concrete building would have been. But according ton Sandra Frank, that’s the wrong way to do the maths.

”We finished this building in just seven months, compared to the neighbouring concrete building in the same shape and style, which took 23 months to finish. That means we can build three wooden buildings in the same time it would take to finish one concrete building. We’re saving a lot of time and money by building houses this way.”

Anna Söderberg, lead architect behind Strandparken, has been in the business for twenty years, mostly working with concrete. She sees a lot of advantages in working with wood.

”Wood weighs only 20 percent of what concrete weighs, which makes it a suitable material when you want to build on top of existing buildings, or on the roof of highway tunnels, which Folkhem is currently doing in Stockholm.”

And there are more advantages. Strandparken, for example, was mostly constructed in a small rural town in northern Sweden, and then transported in pieces to the capital.

This means new jobs and new opportunities in a region suffering from depopulation and unemployment.

Secondly, studies show that people feel so much better living in wooden houses that there heart rate slows down.

But what about the fire risk? Well, historically this was a big issue, but not anymore.

”We used CLT, cross-laminated timber, for the structural panels. If there is a fire, the outer part of the CLT will turn to coal, and that will stop the fire from spreading. It won’t affect the stability of the structure.”

Up until now, 20 000 visitors from 150 counties has visited Strandparken to learn more about the construction process and building with wood in general.

”We get calls from all over the world from construction companies and city planners who wants us to come over and educate them”, says Sandra Frank.

But the building’s fifteen minutes of fame is now coming to an end. In Brumunddal in Norway an 18 floor wooden building called Mjøstornet was recently completed, and in Skellefteå, in northern Sweden, a new Cultural center, 20 storeys high, is to be finished by 2021. All wood.

Interest from city planners are on the rise as well. In Växjö in southern Sweden, the town council has decided that by 2020 every second new building is to be made of wood.

Sweden, having two third of its area covered with trees, may seem unusually well suited for reducing concrete in its construction industry, but wooden constructions are on the rise in many other countries.

Folkhem/Arvet Petra Bindel

In London an increasing number of new buildings have a timber structure, even though this is not easy to spot, since the Brits prefer to cover the facades with bricks. Germany, Austria, Switzerland and Canada are also in the frontline.

But what about countries with little or no forest at all?

Sandra Frank’s solution: Start planting trees.

”This is a global movement. We need to start growing our cities, just as we grow our food. This is the future of construction. There is no doubt about it”, she says.

Written by Markus Lutteman

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