Levers To Reduce Cement’s Use, Along With China’s Slowing Demand, Are A Good News Story – CleanTechnica

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Cement has reared its gray and flaking head into my attention again recently. The global use of about 4.1 billion tons of the stuff to make perhaps 40 billion tons of concrete is responsible for around 10% of all carbon dioxide emissions globally. It’s one of the few industrial products that competes with fossil fuels for sheer, absurd scale, and of course it’s one of the biggest consumers of fossil fuels as well.

Wouldn’t it be nice if we could just avoid using so much of it?

Thankfully, the answer to that question is yes. There are three major levers being pulled by forward thinking jurisdictions and construction organizations, and there’s a bonus lever that forward projections of cements growth seem to fail to account for. (Yes, I sense a decade by decade cement demand, supply, and decarbonization projection through 2100 emerging).

There’s even a good economic reason that means that many of these levers are being pulled with or without climate action. What lever is that you ask? Well, concrete is 11% to 15% of the total cost of commercial buildings. Developers aren’t in the business of charity, they are in the business of profits. Some of the levers involve reducing capital costs and don’t cost nearly as much as they used to, so many more developers are applying them during design to optimize their returns. Of course, the bigger the building, the more likely the developers are to be well informed, well supported with the toolkits necessary for optimization and able to enforce them. Getting a foundation poured for a shed in  your backyard? The contractor is not likely to be using these tools.

First up, are we by any chance wasting any concrete, the stuff cement gets made into? Yes, in two different ways. Estimates are that the average job site wastes 3% to 5% of the concrete it orders. Some of that is through over ordering and then scrapping the stuff. Some of it is spillage. Some of it is concrete forms breaking because they weren’t put together properly. Some of it is delays that lead to the concrete setting before it’s poured.

All of that is amenable to reduction. The biggest lever is software, actually, and that’s going to be a recurrent theme. The industry standard software for designing buildings these days is Revit, and one of the things that emerges with it is the building information management (BIM) model. It’s a tremendous amount of meta-data about everything in the building, and it’s shared — at least on well run projects — with everyone involved so that they can make efficient decisions. Just working up a detailed model and BIM can result in much more precise quantification of the cement required. That over ordering problem diminishes.

Then there are 4D scheduling approaches, once again software-enabled. This takes a model and BIM, and semi-automatically based on obvious things — foundations before walls, lower floors must be in place before upper floors, floors, and walls need to be in place before windows and doors, etc. — establishes the order in which the building will unfold. This often includes animations of the building emerging. This process decomposes the work down so that any day or week’s required concrete will be much better understood, so less of a safety net is required.

Of course, humans will be humans, and worksites will be worksites, so accidents will happen and forms will be messed up. But that 3% to 5% can be cut down substantially. In general, major infrastructure projects like bridges and tunnels will be much more precisely managed, so there’s little opportunity for savings in them, but about 60% of concrete is used in buildings, so there’s a lot of savings to be had. Assuming 2% savings, that turns into about 50 million tons of cement a year in savings at about a ton of carbon dioxide per ton of cement.

But there’s another, hidden problem of concrete waste, over-dimensioning, which is the practice of designing structural elements larger than necessary for safety or performance, leading to excess use of materials and increased costs. Why would anyone do that, you are asking. In a lot of cases, it’s just an excess of caution. There are rules of thumb in civil engineering and construction that aren’t accurate, but do lead to buildings staying up. Some of it is just laziness because doing the engineering work is hard. Some of it is cheapness because structural engineers cost money. Some of it is just because a building collapsing is really bad for business.

Enter finite element analysis software such as ANSYS, Abaqus, and SAP2000, which can perform detailed simulations to predict how structures will respond to various loads and stresses. This helps in designing walls that are appropriately dimensioned based on precise engineering calculations. This software is vastly more available to construction industry professionals than it used to be, including as plugins to Revit. (If you can imagine something an architect or building engineer might possibly want to do with Revit, there are probably a dozen available plugins for it.)

Some studies have found up to 15% concrete savings are reasonable with finite element analysis, as over-dimensioning is so common. Assuming 10% savings on average, that’s 250 million tons of cement, hence carbon dioxide, that could be saved annually. Now we’re starting to see some big numbers.

There’s another emerging toolset for building designers — generative design software. Imagine software which tries out a thousand different designs to find the best performance-to-cost ratio. Machine learning algorithms are now parsing vast amounts of data and suggesting optimized designs from scratch. Real-world case studies are finding 20% to 30% materials savings over buildings (and airplanes and products) designed with generative tools and AI. Assuming 20%, that’s a potential 400 million tons of cement and hence carbon dioxide savings annually for the building sector.

For certain classes of infrastructure, this holds promise for reducing concrete requirements as well, pushing into that 40% that previous options had already seen every lever pulled. The potential for savings increases further.

That’s two levers down, avoiding wastage and optimizing materials. We’re starting to cook with an induction cooktop at this point (cooking with gas is so 19th Century).

The next lever is just not using concrete at all. Sweden and Canada are leaders in mass timber construction, where effectively plywood beams and panels are used as load bearing members — floors and walls — instead of concrete. Sweden allows buildings up to 16 stories high, while Canada allows up to 12 stories.

Mass timber is by definition a durable wood product. It takes trees that have sucked down a lot of carbon dioxide as they grow and turns them into construction material that can last 100 years. When they are taken down eventually, there are approaches to disposal of them that inter the carbon dioxide with them.

A ton of wood sequesters, counterintuitively, about a ton of carbon dioxide. That’s because it keeps the carbon, but returns the oxygen to the atmosphere. Only 37.5% of the carbon dioxide mass is kept, turning into cellulose. Mass timber gets that benefit. With current forestry, manufacturing, and distribution processes, there’s a carbon debt of 0.2 to 0.3 tons of carbon dioxide for a ton of mass timber, which is, after all 97% wood and 3% adhesives. As it stands, mass timber effectively sequesters about a ton of carbon dioxide for a hundred years, and depending on disposal during demolition, can sequester it permanently.

Forestry, manufacturing, and distribution can all be electrified, and the electricity can all be low-carbon. If they are, that 0.2 to 0.3 tons drops to 0.03 tons, or 30 kilograms of carbon dioxide for a ton of mass timber that has sequestered a ton of atmospheric carbon dioxide. Building with mass timber turns buildings in carbon sinks, not carbon wells.

Buildings that are 12 stories or taller represent approximately 0.0045% of all buildings in the United States, about 6,000 of the 131 million buildings. Europe has significantly fewer high-rise buildings compared to regions like Asia and North America. While China has a lot of bigger buildings, a coarse estimate suggests that at least 94% of buildings are still under 12 stories. The vast majority of new buildings are amenable to mass timber construction techniques.

Coincidentally, modern mass timber construction uses the BIM to manufacture the beams, walls, and floors in factories. 4D scheduling lays out the order of construction, delivery, and installation. They are then delivered to sites and slotted into place like very big, very heavy LEGO pieces, but without the bright colors or chance of stepping on one barefoot in the dark.

Concrete is still required for foundations, but mass timber even cuts back on that as mass timber is lighter than the usually reinforced concrete it replaces. That results in 20% to 30% savings in the amount of concrete required for the foundation of the building. And of course, there’s no concrete to speak of in the rest of the building.

Hybrid buildings taller than the limits are not only possible, but multiple have been built. Concrete is used for the foundations and load bearing structures, but the walls and floors are mass timber.

Total savings for full mass timber buildings are 60% to 70% of concrete, while hybrid buildings still see 40% to 50% reductions. Of course, a few big buildings make up for a lot of small buildings. Remember, 60% of 4.1 billion tons of cement is used in buildings. Even in China, perhaps 94% of new buildings could be constructed with full mass timber and the rest could be mixed.

Of course, we already use wood for a lot of things, about two billion metric tons a year. However, a rough workup estimate, and hence coarse, just now suggests 500 to 700 million tons are for single use products such as pallets (over 90% of solid wood waste in US landfills), paper towels, and tissues which could be pivoted to multi-use products. 200 to 300 million tons are simply burned, a nonsensical act in my opinion and something which will likely diminish as more and more heat is electrified. Call it 500 million tons of wood available for mass timber from repurposing current forestry levels for better ends.

Expanding sustainable forestry for this strong climate and environmental benefit makes sense. Let’s assume another 500 million tons of wood can be harvested sustainably. That’s a billion tons of engineered timber. Would that be enough to make a dent in the perhaps 25 billion tons of concrete used in buildings annually? It doesn’t look like it does it.

But mass timber has one more trick up its sleeve. Its strength to weight ratio is a lot better than concrete. Using it for the same purposes — where applicable, not foundations — saves 80% of the weight over concrete. That means that billion tons is actually equivalent to about 4.8 billions tons of concrete, about a fifth of the annual use.

That’s a wedge that could displace around 600 million tons of carbon dioxide a year and sequester in durable wood products for a 100 or more years about a billion tons of atmospheric carbon dioxide. Now that’s an atmospheric carbon drawdown wedge that makes sense. Even half of that is worth striving mightily for.

There’s another way to avoid using concrete, of course. Reuse existing buildings instead of tearing them down and building new ones in their place. As I found when looking at Sublime Systems’ cement process, there are about 2 billion tons of concrete waste from demolition annually around the world. Most of that is from buildings, as infrastructure is built to last. Call it 85%. If 25% of the buildings were reused and renovated instead of demolished and new ones built, that’s another 20% wedge in concrete and hence cement use. The greenest building is the one that’s already built is the mantra applied to this wedge.

All of these levers are coming into sharper focus with combinations of carbon pricing and regulations regarding carbon debt per cubic meter. A ton of cement in 2030 under the EU’s emissions trading scheme guidance will cost about €200 more. In Canada, it will cost CA$170 more. Those costs double the cost per ton of standard Portland cement. When 11% to 15% of a building’s cost jumps to 18% to 23%, every cost-saving trick in the book will be used much more stringently. Mass timber comes with a bit of a cost premium right now, and this makes it very competitive.

Multiple jurisdictions have introduced regulations to limit carbon debt in buildings, including China, the EU, the UK, Canada, and cities in Canada. Standard wasteful concrete construction techniques need not apply if they want to be permitted.

I promised a bonus item, and back we go to China. In 1990, China produced about 210 million tons of cement annually. In 2023, it produced 2.1 billion tons, a full ten times more. China used more cement in 2023 than the rest of the world combined, as is the case for an enormous number of other things, like steel.

However, linear projections of cement growth start with the assumption that China’s demand will continue to rise, when in fact China has finished the majority of its infrastructure and building program. It has 177,000 kilometers of highway when none existed in 1987. It has 45,000 km of high-speed electric rail, up from about zero in 2007. It has absurd numbers of cities that didn’t exist in 1990 in anything like major urban centers, and while the number of ghost cities has plummeted, migration from rural to urban areas is still under way and there are still underpopulated cities with full transit and infrastructure.

Just as with my steel projections through 2100, I project a reduction in China’s cement demand. That will be counterbalanced by an increase in cement and concrete, especially in Belt & Road Initiative countries — about three-quarters of the countries on the planet including lots in Eastern Europe and Latin America as well as rapidly developing economies like Indonesia, India, and Brazil. Overall, I’m debating whether cement demand globally will be flat or go down. I suspect we’ll actually see it go down, as the rapidly developing countries don’t have the conditions for the insanely rapid development China shot through over the past 40 years.

If we assume a decline to 3.5 billion tons of cement annual demand as a baseline, and then start displacing cement with these other measures, napkin math suggests actual cement demand might drop to 2 billion tons a year. That’s about two billion tons less of carbon dioxide into the atmosphere annually and only two billion tons of cement we have to decarbonize to get to end of job. That’s a good news story.