American Cement and Concrete Industry Releases Road Map to Carbon Neutrality

The Portland Cement Association (PCA) represents the majority of cement and ready-mix concrete companies in the U.S., and it has a problem: making cement produces a lot of carbon dioxide (CO2). To deal with this, they have just issued the "PCA Roadmap to Carbon Neutrality." The PCA notes: "The PCA Roadmap involves the entire value chain starting at the cement plant and extending through the entire lifecycle of the built environment to incorporate the circular economy."

Before we get into their detailed plans, let's look at some definitions and assumptions as they are important for understanding the road map.

The Chemical Fact of Life

Going carbon neutral with cement is a real challenge, because of the basic chemistry of cement. In the report PCA actually calls it the chemical fact of life:

"The fact that even if the industry were to eliminate all combustion emissions, the chemical process used to manufacture clinker creates a separate stream of CO2 emissions. For example, in the U.S., 60% of the CO2 generated by cement plants is from a chemical reaction called calcination. Calcination is the chemical fact of life in that it is the first step in a required series of complex chemical and physical changes to make cement. The chemical fact of life is also called“process emissions."

Or as I explained in my book, "Living the 1.5 Degree Lifestyle":

"The key component of cement is lime (calcium oxide), which you get by applying heat to calcium carbonate, basically limestone.

CaCO3 + heat > CaO + CO2

You can’t do anything about the chemistry. You can use less lime and substitute fly ash and pozzalan (what the Romans used, basically volcanic ash) and reduce the carbon footprint somewhat. But it is the fundamental nature of the material that making it emits CO2."

Mix that up with clays and a bit of gypsum and grind it into a fine powder and you get Portland Cement, named after the English Isle of Portland where the original limestone came from back in 1824. Add it to aggregates–sand and gravel–and water, and you get concrete.

Carbon Neutrality

The road map calls for carbon neutrality by 2050, but this is a nebulous term that I noted in an earlier post is not used much anymore, with net-zero being more popular. But the term is used all through this report, and it is first defined on page 18:

"Carbon neutrality is achieving net-zero CO2. This can be done by balancing emissions of CO2 with removal or elimination of emissions from society. The reality is that the cement and concrete industry will still be emitting CO2 in 2050. However, through direct reductions and avoidance measures, the industry can offset its remaining CO2 emissions."

The road map also has a definition at the end of the report:

"Carbon neutrality: The principle by which CO2 emissions resulting from a product or process are offset either by direct CO2 emissions reductions or through avoided CO2 emissions."

I find this to be a confusing definition and have asked for clarification because emissions reductions or avoided emissions do not sound like offsets. They do talk about direct carbon capture and storage as a way of reducing emissions, and these are considered offsets.

How much CO2 does the industry produce?

The PCA acknowledges that the manufacture of cement accounts for 1.25% of U.S. CO2 emissions. Others say it is much higher than that; even their own documents say cement accounts for 3% of industrial emissions. The U.S. imported 15 million metric tons of cement in 2020 and manufactured 88 million metric tons, emitting 900 kilograms of CO2 per metric ton, so whether it is 1.25 or 3%, it is still a lot of CO2.

Worldwide, according to Carbon Brief, cement production is responsible for 8% of global emissions, but they use massive amounts of the stuff in China and they are responsible for most of it.

So what's the road map?

The authors of the road map freely admit that there is no "silver bullet." They write: "In 2021 there is no single process, product, nor technology that can get the cement and concrete industry to carbon neutrality."

So they are attacking it on all fronts, going at each stage of the lifecycle, from clinker to carbonation, through the whole value chain.

Some of these make obvious sense, such as using decarbonated materials like construction and demolition waste, where they grind the concrete down to a mixture of cement powder and sand. Other materials like fly ash can reduce the amount of calcium carbonate needed to make cement.

Alternative fuels are a bit less wonderful or more fanciful: "These fuels range from cellulosic biomass to non-recycled plastics, residuals from paper and cardboard recycling, and agricultural wastes – all opportunities to give spent materials a second, productive life." Burning garbage produces more CO2 per ton than burning coal. And burning plastic is considered to be equivalent to burning fossil fuels that have taken a short side-trip through your take-out container. Getting the dioxins and other toxic chemicals out of the exhaust is difficult and expensive.

Then there is carbon capture and storage (CCS). We are talking vast amounts of CO2 in the flue gases and the technology doesn't yet exist at scale or affordable prices. The road map admits this, noting: "There are no commercial-scale CCUS installations at any cement plant within the U.S. To do so will require significant investments in research."

All of the suggestions in the design and building section make sense, no matter what you are building out of, particularly avoiding overdesign. The days of my beloved Brutalist concrete buildings are over. The road map envisions that optimization can reduce emissions by 30% by 2050.

There is much to admire in this report: It represents a serious attempt at a road map to reducing the carbon footprint of concrete. As Bill McKibben said about climate change, “There are no silver bullets, only silver buckshot.” It takes aim at every facet of the industry.

But if this is a road map to carbon neutrality, there are a lot of gaps in the map, a lot of "there be dragons" off at the edges. There is not a single drawing that actually shows neutrality. At best, we see a reduction in CO2 per cubic yard of about 60% but that is a long way from zero.

Without saying it out loud, the implication from reading policy priorities like "accelerate research, development, and commercialization of at-scale carbon capture solutions for industrial sources" and "invest in and incentivize creation of national carbon capture, transport, use, and storage infrastructure" implies they are relying on carbon capture and storage to make up the difference. That's a big bridge in this road map, what looks like about 40% of emissions. It's a long very road to carbon neutrality.

The Time Value of Carbon

The report talks a lot about how well concrete does on full lifecycle analyses and how recarbonization—the absorption of CO2 into existing concrete—is significantly underestimated, suggesting that as much as 10% of emissions are reabsorbed over the life of a building. This all may be true, but every kilogram of CO2 that goes into the atmosphere goes against the carbon budget that we have to stay under to keep the global temperature rise under 2.7 degrees Fahrenheit (1.5 degrees Celsius).

We don't have lifecycles to think about, we don't have time for recarbonization. We have to reduce emissions now. It's what's known as the time value of carbon—"the concept that greenhouse gas emissions cut today are worth more than cuts promised in the future, due to the escalating risks associated with the pace and extent of climate action."

So carbon emissions happening now are critical, yet cement production in the U.S. has increased every year since 2010. Even as it gets cleaner, we are using more of it.

It's pretty clear that we are always going to need concrete, and the concrete we use will get progressively better. But in the end, it is pretty hard to change the chemical fact of life, that making cement releases a lot of CO2, and the only way to deal with that appears to be to suck the CO2 out of the flue with carbon capture and storage, which doesn't currently exist. and we can't wait to find out if it will.

So it is a great road map, but it is driving us on to a long diversion. We have to use a lot less cement and concrete starting right now.