Here's a fun fact for you.
Between 2011 and 2013 China used more cement than the USA used in the entire 20th century.
And they're still going gangbusters now they've got through their pandemic lockdowns.
In 2021 they produced 2.5 billion tons of the stuff.
That's more than the rest of the world put together.
And that's a problem because with current production methods every tonne of cement results
in a tonne of carbon dioxide emissions.
It's not just China though, obviously.
As a relatively cheap, extremely strong, and incredibly versatile material, cement - or
more accurately concrete that it's made from - is ubiquitous all over the world.
In fact it's the second most consumed product on earth beaten only by water.
In total, concrete accounts for eight percent of all global carbon dioxide emissions.
So it is a problem, and to be fair it's a problem that the cement industry is acutely
aware of.
The question is what are they going to do about it?
Hello and welcome to Just Have a Think.
We had a look at the cement manufacturing process in a video a couple of years ago and
it's probably worth taking a quick recap here.
The first step is to grind up limestone, otherwise known as calcium carbonate, with additional
materials like clay, slate, silica, sand and iron ore, and throw it all into a massive
rotating kiln at something like 1500 degrees Celsius.
The kiln is tilted at an angle and as the mixture goes from the higher end to the lower
end various elements are driven out to form a new substance at the bottom called clinker,
which comes out of the kiln as little grey balls about the size of marbles.
A small amount of gypsum and limestone gets added in with the marbles and then they all
get ground up into the fine powder that we know as Portland cement.
The chemical reaction for that process looks like this, with carbon dioxide as one of the
main outputs.
And to get to the high temperatures required by the kilns, fossil fuels like powdered coal
are often used, which results in even more CO2 emissions.
In 2020 member companies of the Global Cement and Concrete Association produced what they
described as their Road Map to Net Zero Production by 2050.
Those companies include the world's largest cement manufacturers like Lafarge Holcim,
Heidelberg and China National Building Materials.
The roadmap is a 48-page document containing graphics and charts like this one showing
the intended trajectory for the industry's emissions reductions.
Apparently according to the wording of the chart they are currently two years into what
they call 'the decade to deliver' but judging by the very next graphic in the document no
less than 58% of those reductions rely either on designers and architects coming up with
smart ways to use and reuse concrete in construction or on the largely unused and unproven concept
of carbon capture utilization and storage otherwise known as CCUS.
Another six percent of carbon reductions are attributed to concrete's propensity to absorb
a bit of carbon dioxide back into its structure over long periods of exposure to the elements.
Five percent relies on the decarbonization of electricity by grid operators and eleven
percent will apparently come from greater production efficiencies and quality control.
That means that only 20 percent of the total decarbonization proposed by the global cement
industry is planned to come from actually decarbonizing the cement material itself.
But more and more zero carbon or green cement technologies are now being developed around
the world and several of them are already in production and being used.
So how do they work, and can they shift this percentage by becoming market disruptors in
the construction industry?
Solidia is a start-up company based in New Jersey.
They produce cement in traditional kilns but with a 50: 50 ratio of limestone to sand instead
of two-thirds to one-third.
That means the reaction can run at a much lower temperature which reduces energy use
by about 30 percent and greenhouse gas emissions by as much as 40 percent.
During the curing process carbon dioxide is injected into the mix instead of water.
That reduces the reaction time from more than a week to only 24 hours.
The injected CO2 is then trapped in the final solid product resulting in a claimed net overall
CO2 emissions reduction of up to 70 percent.
The product has been used all over the world but still at relatively small scale.
The biggest limitation of this technology right now is that it can only be produced
in a factory environment to make blocks of cast concrete.
That's fine for things like paving slabs and breeze blocks but it's no good for ready-mix
pourable concrete which currently makes up almost 75 percent of all concrete use globally.
Solidia are mindful of that though, and they say they're working hard on the development
of a ready-mix version to bring to market very soon.
Another way to tackle the problem is to take a bottle of CO2 gas to a concrete mixer and
simply inject it into the ready-mix material.
That's essentially the strategy of a company called Carbon Cure.
They source their CO2 from industrial emitters, purifying it and then distributing it to concrete
sites in pressurized tanks that can be regularly refilled, just like your Sodastream canister
at home.
As it's injected into the fresh concrete a mineralization process embeds it permanently
into the material.
The additional CO2 in the mix has the handy benefit of increasing the compressive strength
of the concrete.
Carbon Cure claim that 17 kilograms of CO2 can be saved for every cubic metre of concrete
produced.
Their website tells us that more than 3 million truckloads of their concrete has already been
used in the construction industry, saving nearly 200,000 metric tons of CO2 emissions
so far.
Technically this is one of those CCUS methods that I mentioned earlier so it's still not
fundamentally altering the way that cement and concrete are produced in the first place,
which arguably means it's open to a bit of figure fudging.
But if it's implemented correctly, the way Carbon Cure have designed it to be, then there's
a good chance they could meet their stated goal of removing 500 million tons of CO2 per
year from the exhaust stacks of industrial polluters.
That'd be the same as removing 100 million cars from our roads.
Carbicrete is another name you may have heard of.
They use a system called Carbonation Activation, which eliminates the need for cement in concrete
altogether by replacing it in the mix with ground steel slag, which is a by-product of
the steel making industry.
Their concrete mix is poured into moulds and cured using CO2.
That curing process solidifies the CO2 and binds it together with the steel slag granules,
which gives the concrete its strength.
Just like Solidia, Carbicrete's technology is currently limited to precast slabs and
components but it does represent a fundamentally different method for producing a concrete
binder which eliminates the high carbon Portland cement used today.
Carbicrete claim to capture about two kilograms of CO2 in a standard size concrete block which,
in a typical US production facility making concrete masonry units or CMUs, would mean
a reduction of 20,000 tonnes of carbon dioxide emissions, plus a saving of about 4.4 million
litres of water and the avoidance of 33,000 tons of landfill a year.
A couple of new names have joined the fray recently too.
Sublime Systems was founded by an MIT electrochemist called Leah Ellis and an entrepreneur called
Yet Min Chiang.
They say they've addressed both the carbon emissions from the cement calcination process
and the carbon emissions from the heating sources by developing an electrochemical solution
that can do the job at ambient temperature.
That significantly reduces the energy input requirement and it makes it far easier to
capture the resultant CO2.
And because the process is entirely electrical it can potentially be powered by 100% renewables,
making the whole thing carbon neutral.
It's still early days.
The company currently produces at a rate of only kilograms per hour, but they're in the
process of scaling up to tons per hour.
Ellis and Chiang are pragmatic though.
They know it'll take time to change attitudes within the industry.
"The challenge is humbling" Ellis said in this recent interview "but the opportunity
is enormous."
Brimstone is yet another US start-up with yet another concept for solving the carbon
emissions problem.
Their process is exactly the same as a traditional Portland cement manufacturer except that Brimstone
don't use limestone as one of their raw materials.
They use different rocks that contain calcium.
Basalt is one example that most of us have probably heard of, but there's lots of different
types, and in total they're actually much more commonly available than limestone.
These rocks are calcium silicates not calcium carbonates which means they don't release
carbon dioxide when they're converted into cement.
So if it's that simple to fix the problem why don't all cement makers use these rocks
then?
Well it turns out that the final cement product that gets into concrete contains a good percentage
of fly ash which is a waste product from burning coal, so historically there's been a useful
symbiotic relationship between the cement industry and the fossil fuel industry to make
some economic use out of an otherwise redundant waste stream.
And of course, when nobody cared about CO2 emissions and global warming, there was absolutely
no incentive whatsoever to upset what was a nice cosy relationship between two major
industries.
There is now though, not just because of climate change but also because the reduction in coal
burning means fly ash is becoming harder to source and therefore more expensive.
The proprietary process that the Brimstone team have developed actually co-generates
fly ash at the same time as Portland cement, from a single rock at a single site.
Their research was initially carried out at the Lawrence Berkeley National Lab and funded
by the US Department of Energy, but more recently they've won investment from several venture
capitalists, including Bill Gates's Breakthrough Energy Ventures.
Brimstone don't provide exact costings for their process but they claim it's significantly
cheaper than existing methods.
The company is building a pilot plant as we speak which may produce about a thousand tons
of cement a year, but the real plan is to license their technology to as many existing
cement makers as they can find all over the world with the aim of decarbonizing the industry
as quickly as possible.
So you know, in theory it's all there for the taking.
It just needs existing cement manufacturers and the global construction industry to genuinely
throw their weight behind these relatively small scale start-ups, put some serious funding
in place, and start utilizing these low carbon alternatives straight away.
It'll also require rapid testing and integration into building codes all over the world so
the traditionally very conservative and quite rightly very safety conscious developers can
have the confidence that these products are a robust and durable plug-in replacement for
traditional concrete.
If you've got news or views on these potential market disruptors then why not jump down to
the comments section below and leave your thoughts there.
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