Decarbonizing a concrete problem: a blueprint to net zero cement

Hi! I’m Liza Rubinstein, Co-Founder & Head of Impact at Carbon Equity. In this newsletter, I discuss decarbonizing our cement problem and more. This edition is 1,342 words or a 5-minute read.

Did this email get shared with you? You can sign up here.

⚡️ Decarbonizing a concrete problem: a blueprint to net zero cement

Did you know that if concrete were a country, it would be a top-five CO2 emitter worldwide? Below, I’ll explain where these emissions come from, what makes getting rid of them so hard, and which innovators are working on solving the problem.

A concrete challenge

Concrete is the second-most-used substance in the world after water.* Worldwide, 30 billion tons of concrete are produced yearly — and the demand for concrete is growing more steeply than steel or wood.* Concrete is already responsible for 5% of all human GHG emissions, while only three-quarters of our 2050 infrastructure has been built.*

Concrete is made by mixing cement, sand and gravel. Cement makes up only 12% of the volume of the concrete mix but is almost solely responsible for the CO2 emissions of the material.

Cement’s carbon-intensive process

Complex cement process, Source: McKinsey
Source: McKinsey

Cement production creates its CO2 emissions from two primary sources:

  1. Fuel combustion (40%) Limestone is heated in kilns to temperatures up to 1450°C. Typically, fossil fuels (coal or petcoke) are burned to produce this heat, creating CO2 emissions.
  2. Calcination reaction (50%) The conversion of limestone to quicklime happens through calcination, a chemical reaction. This reaction produces CO2 as a byproduct.

The last 10% of emissions are from transportation and the electricity used.

So, how do we solve it?

Given the industry's diverse applications (bridges, buildings, pavement, dams, etc), varying types of cement per application, and two main emission sources, there is no single solution or "silver bullet" to decarbonize cement.

Creating a blueprint for getting this industry to net zero requires a multifaceted approach that includes demand-side interventions, supply-side strategies and the adoption of new, innovative technologies.

On the demand side, it comes down to reducing and substituting. On the supply side, we have short-term and long-term tech improvements:

Short-term tech improvements

  • Clinker substitutes
    Clinker is a mix of limestone and minerals heated in a kiln. Substituting clinker with alternative materials can significantly reduce emissions. Terra CO2 uses a mix of silicate rocks, like granite, basalt, glacial flood gravel and clay-sand mixtures, which it estimates can result in 70% lower CO2 emissions than pure Portland cement.*
  • Alternative combustion fuels
    Alternative fuels (from biomass or old tires) are commonly co-processed with fossil fuels in the cement industry; however, the emissions reduction potential is typically limited (due to certain chemicals impacting the hardening process) to about 1-5% in most cases.*
  • Carbon capture, utilization and storage (CCUS)
    With CCUS, CO2 emissions are captured and stored or used. Several pilots are already running; however, CCUS for cement is challenging as the emissions from burning fuels and the chemical reaction get mixed. Some innovations separate those out but still only solve half the challenge.*
  • Injecting CO2 into concrete
    CO2 can be incorporated into cement after it's produced. This not only stores it permanently but also makes the cement lighter, reducing the amount needed and its carbon footprint. CarbonCure (in our Built Environment Fund) is leading the way in this innovative technology.
  • Software applications
    AICRETE combines data and AI with automation and extensive domain knowledge to develop new concrete mixtures. Carbon Re provides software for industrial decarbonization to uncover energy efficiencies and reduce costs.

Long-term tech improvements

The next generation of technologies is under development, which can decarbonize cement fully. However, most of these will need more time and investment than the previously mentioned technologies.

  • Electrolysis and hydrogen application
    Sublime Systems
    (in our Climate Tech Portfolio Fund I) skips the calcination process, responsible for half of cement CO2 emissions, using alternative calcium sources. It uses an electrochemical process that turns abundantly available non-carbonate rocks and centuries of industrial waste into calcium sources that don’t release CO2 when decomposed. The rest of its blending process occurs at ambient temperatures, meaning it doesn’t involve any fossil-fuel-burning, high-temperature kilns.
  • Nature-based solutions
    (in our Climate Tech Portfolio Fund I) is developing a bioreactor in which microorganisms ferment limestone into a natural cementitious material, removing 75% of emissions compared to Portland cement. Minus Materials grows carbon-negative, bio-renewable limestone using calcifying microalgae. The limestone can be directly used in the production process as is, yielding a 60% CO2 emission reduction.
  • Innovating the traditional process
    has developed a new process to make cement using basalt and other calcium-bearing silicate rocks instead of limestone.* These replacement rocks are rich in calcium oxide, a key ingredient in cement-making, but they don’t contain any carbon atoms. Its process also produces a magnesium compound, which binds with CO2 to remove it from the atmosphere permanently.

The hurdles to net zero

Three key factors hinder the progress of innovative cement companies:

  1. A critical lack of funding remains a hurdle for scaling capital-intensive cement startups, limiting their ability to bring their innovations to market.
  2. Regulatory delays in approving new production methods and cement types slow innovative cement tech from getting to market. Shifting from recipe-based standards to performance-based ones could accelerate this process.
  3. The conservative cement sector is challenging to disrupt due to high barriers to entry, low margins and powerful incumbents. To get to net zero, we need these incumbents to innovate themselves or acquire innovative tech (startups or scaleups) and bring them into their embedded infrastructure and supply chains.

Building upon the positives

Governments are making important progress in decarbonizing cement. The US Inflation Reduction Act and the EU ETS, which increases the cost of carbon, provide financial incentives for the cement industry to innovate and reduce emissions. EU cement companies are already updating their commercial strategies for recycled and low-carbon cement products.*

More of the private sector has also started to move under the First Movers Coalition, which mobilizes companies to decarbonize hard-to-abate sectors (including cement) by committing to purchase from zero-carbon suppliers.

The blueprint to net zero requires multiple key stakeholders. But if governments, corporates and investors continue to work together, there's a clear pathway to overcome the cement industry’s emissions and solve this climate challenge.

You can read my full deep dive on the concrete/cement problem here.

🚀 News from within our funds

Mojave produces a liquid desiccant air conditioning platform that cuts in half the energy required to provide buildings with fresh, cool and dry outdoor air. We joined its $12.5m funding round through At One Ventures.

Umiami leverages its unique protein texturizing process, “umisation,” to make plant-based whole cuts, like chicken breasts. It recently received an additional $32.5m in Series A funding, which we joined through Astanor Ventures.

Trove provides the platform that powers the resale and trade-in ecosystem for brands. We joined its €30m funding round through ArcTern Ventures.

AtmosZero, which we invested in through Energy Impact Partners, makes a boiler with a 100% efficiency gain to electrify hard-to-decarbonize industrial heat. It announced its expansion into Europe, with its first subsidiary based in Amsterdam.

You can explore more companies within our funds here.

💡 Carbon Equity updates

We recently secured €6 million in Series A funding led by BlackFin! The capital will be used to scale up international expansion, grow our distribution channels and lower minimums to €25,000. You can read more here.

Series A press release newsletter

We also announced our expansion into Belgium! 🇧🇪 You can read more about our ambitions and what it means for Belgian investors through our feature in De Tijd here. As part of our Belgium launch, we are hosting our first event in Antwerp on November 22. You can apply for the event (in Dutch) here.

Jacqueline, our Co-founder and CEO, was named to this year’s Top 50 most influential women in Sustainable Finance (see here) and appeared on BNR (listen here).

I'm excited to be a keynote speaker at Elfin’s first live event (in Dutch) on November 9, discussing how you can invest with impact confidently. You can buy your ticket here.

📚 Interesting reads

PwC’s State of Climate Tech 2023

The need for climate tech continues to rise, but global climate tech investments declined for the second year in a row, dropping by 40% in 2023 and taking funding levels back to where they were five years ago. The reason? Tough conditions in private markets, general VC is down 50%. On the bright side, the capital invested is going to hard-to-decarbonize sectors where it’s needed most.

Energy transition is the ‘new industrial revolution’

John Kerry, the US climate envoy, outlined his key financial priorities for the upcoming COP 28: (1) the need for the World Bank to increase its lending capacity to aid developing countries in transitioning away from fossil fuels, (2) the importance of expanding the voluntary carbon market to reach necessary levels of concessionary funding, and (3) the need for other regions to imitate the Inflation Reduction Act.

The Eight Deadly Sins of Analyzing the Energy Transition

The renewable energy revolution is growing rapidly, yet analysts often underestimate the pace and scale of innovation. This article pinpoints eight common errors causing these underestimations, such as linear thinking, fixating on existing infrastructure and overlooking the importance of energy efficiency. Recognizing its growth accurately is vital for accelerating our progress, as we shape the future we anticipate.

Why deploying climate tech at scale is so hard

Climate tech startups face at least four 'valleys of death'. To scale, it must (1) spin out the technology and form a startup, (2) find product-market fit, (3) demonstrate the first full-scale commercial facility, and (4) scale up from there. Attracting the billions required to scale has become harder with higher interest rates, especially for innovative companies without a supporting value chain or infrastructure.

Biochar is a proven form of carbon removal. Can it scale up?

Biochar, made by burning organic waste without oxygen, can store CO2 for hundreds of years or more. It's the main method used for carbon removal to date.* The problem is deciding where to use it. While biochar can improve soil fertility, farmers don't buy it because it's not standard practice. The move towards regenerative farming may help with this — other uses, like adding it to asphalt, are being explored.

I'd love to hear from you! 🙂

newsletter feedback