Green Cement Can Have A Key Role Addressing Climate Change. How Can We Accelerate Cement Innovation?
10,000 years ago, in present-day Turkey, ancient innovators mixed the first known form of cement. In the millennia since, cement enabled the construction of the Hagia Sophia, the Colosseum, and Hoover Dam, and today it is the most widely used material in the world.
Now modern innovators are working to transform this classic technology. While cement is cheap, versatile, and reliable, it is also a major contributor to climate change, accounting for 8% of C02 emissions — more than all cars (6%) and planes (2%) combined.
In the United States, cement is on the agenda as policymakers debate ways to upgrade infrastructure and address climate change.
More broadly, climate risks could increase as worldwide demand for cement booms. By 2050, 2.5 billion more people will live in urban areas, and the world’s stock of buildings is expected to double by mid-century — the equivalent of constructing a new New York City every month for 40 years.
How can producers meet the demand for building materials while helping to reduce climate risks?
Cement is the glue in concrete — binding together a mix of sand, gravel, and water — and its production emits C02 mainly in two ways.
First, making cement requires heating limestone in a kiln to 1600°C. To reach that high temperature economically, producers usually burn coal or petroleum coke, both high in emissions.
Then, emissions are released from the chemical reaction inside the kiln, as limestone breaks down into its constituent parts, including lime and CO2. The lime is used to make cement and the CO2 is released into the atmosphere.
There has already been significant progress toward reducing the carbon intensity of cement production — an 18% decrease on a per-unit basis since 1990 — but researchers are working toward greater breakthroughs. Here’s a snapshot of some of the many advances that, though in early stages, could transform cement.
A natural place to start cement’s transformation is with the fuel to produce it.
Cement producer Hanson UK launched a pilot program using green hydrogen to replace coal and coke. Green hydrogen is made using electrolysis to split water into hydrogen and oxygen. Hanson UK powers its electrolysis with renewable energy and then uses the hydrogen to fuel its cement production. Green hydrogen produces no direct C02.
Improved cement blends and substitutes
Since the reaction of breaking down limestone into lime releases C02, researchers are working to use less lime.
For one, a team at the Swiss Federal Institute of Technology has developed LC3, or Limestone Calcined Clay Cement. Calcined clays release smaller amounts of C02 than traditional materials, and the Swiss LC3 blend reduces CO2 by 30%–40%.
More ambitiously, the Australian company Zeobond is aiming to move beyond lime altogether using what is known as geopolymer cement, a compound based on aluminum and silicon. Geopolymer cement results in 80–90% less C02.
Instead of reducing CO2 directly, some approaches use carbon capture to trap it.
In 2014, Skyonic, a company that makes carbon capture technologies, opened the Capitol SkyMine at a San Antonio cement plant. This first-of-its-kind facility traps 75,000 tones of CO2 annually or 90% of the plant’s emissions. The CO2 is reprocessed for other products, like bleach and baking soda.
Since 2014, the use of carbon capture in cement production has increased, and the world’s largest cement company, LafargeHolcim, recently joined an industry initiative to use the technology in more of its operations.
New Jersey-based Solidia Technologies is flipping the problem of cement emissions on its head.
Ordinarily, cement is cured — or, hardened — by adding water to powder that hardens as it dries. Instead of water, Solidia’s cement is cured inside a drying chamber filled with CO2 which is then absorbed into the cement and trapped in the final product, turning cement itself into a carbon sink.
Solidia’s curing process and other advances reduce C02 emissions by up to 70%.
Can low-carbon cement scale?
Today low-carbon cement products are either in pre-market phases or niche products. Addressing the climate risks of cement while meeting the demand for building materials will require an exponential increase in low-carbon cement.
The main barrier is cost. Low-carbon cement has a high green premium — added cost to buy a product with a reduced climate impact relative to a standard alternative — typically costing 75% to 140% more than traditional cement.
The low-carbon cement market is growing as the technologies mature and costs fall. One study estimates the low-carbon cement market will double from $21 billion now to $44 billion in 2027. The low-carbon cement market is also increasing at nearly twice the rate as cement overall.
However, low carbon products will still only be about 10% of the total cement market by 2027.
What would aid the adoption of low-carbon cement? Part of the answer is in a range of private and public sector efforts to support cement R&D and incubate new companies — bringing down costs over time.
In 2019, a group of 30 leading cement companies formed Innovandi, a consortium to fund, coordinate, and incorporate carbon reduction technologies into cement production. Similarly, Bill Gates-backed Breakthrough Energy is investing in early-stage cement companies, such as CarbonCure, to accelerate their growth.
The U.S. Department of Energy is also supporting university-based projects, including an experimental approach at UCLA that could produce cement with 50–70% less C02 while competing on cost.
At a time when policymakers are aiming to modernize infrastructure, there is bipartisan support for efforts to boost low-carbon cement.
The Biden Administration has called for more funding of low-carbon cement R&D, and the Senate’s bipartisan Climate Solutions Caucus — led by Chris Coons (D-DE) and Mike Braun (R-IN) — endorsed similar proposals, like investing in more carbon capture for cement production.
Policymakers should build on this common ground, uniting to increase public funding for R&D and gradually expand the use of low-carbon cement in infrastructure upgrades.
In the short term, using more low-carbon cement would add to the cost of infrastructure, even as it helps the industry mature. So, policymakers can offset some of the cost by streamlining the approval process for construction projects and modernizing building codes, which at times slow the adoption of low-carbon cement.
Building codes — usually enacted at the local level — often specify a precise formula for what cement can be used, which can inadvertently exclude low-carbon cement even when it is just as safe as traditional cement. These codes must be updated more rapidly as cement evolves, helping to reduce the costs of project delays.
These are just some of the efforts needed to transform cement. Doing so will require the engagement of people from all walks of life — from chemists inventing breakthroughs to business leaders and policymakers scaling technologies to construction workers mastering new materials.
Over thousands of years, people have always found ways to adapt cement to new purposes, harnessing Earth’s basic elements to build civilizations. In meeting the challenges ahead, we can demonstrate that ingenuity yet again, creating a strong and safe foundation for the future.