Cement kilns need to run at temperatures above 1,400°C, and for most of the industry’s history, that heat has come from one place: fossil fuels. Coal and petroleum coke are cheap, reliable, and available almost anywhere, which is exactly why they became the default fuel for clinker production. It is also why fuel choice is one of the biggest levers a cement producer has for cutting emissions, right alongside clinker reduction and Carbon Capture, Utilization and/or Storage (CCUS)..
The good news is that this lever is moving faster than most people realize. According to the International Energy Agency, fuel combustion accounts for roughly 35% to 40% of the cement sector’s direct CO2 emissions, and unlike process emissions from calcination, these are emissions the industry can address today, without waiting for a new chemistry to mature. Three technologies sit at the center of that shift: waste gasification, enhanced combustion, and low-carbon hydrogen production. They are related, but they are not the same thing, and understanding the difference matters if you want to know where the sector is actually heading.
None of this is a purely academic distinction either. A plant that wants to raise its share of alternative fuels quickly runs into a practical wall: solid waste burns unevenly, hydrogen has to come from somewhere, and the combustion system itself must remain stable enough to keep producing clinker of consistent quality. The three levers explained here exist precisely because each one solves a different piece of that puzzle, and together they explain why fuel transition has become one of the fastest moving areas of cement decarbonization.
What Is Fuel Transition in Cement Production?
Fuel transition, in the context of cement manufacturing, means replacing fossil fuels such as coal and petroleum coke with alternative sources that emit less carbon, without compromising the extreme heat and process stability a kiln needs. It is usually measured through the thermal substitution rate (TSR), the share of a kiln’s thermal energy that comes from non-fossil sources.
That single number hides a lot of complexity, and a lot of opportunity. A 2026 operational guide compiled from GCCA, PCA, and IFC data shows that European plants already average a 52% thermal substitution rate, while plants in the United States sit closer to 16%. The gap between leaders and laggards is not about access to exotic technology. It is about which plants have committed to building the fuel supply chains, and the combustion systems, that make higher substitution rates possible.
Waste Gasification: Turning Residual Waste into Kiln Ready Fuel
Waste gasification is a thermochemical process that converts solid waste, biomass, or industrial by products into a combustible gas called syngas, short for synthesis gas, by heating the material in a low oxygen environment instead of burning it directly. The result is a gas that can be fed straight into a kiln burner in place of pulverized coal, with far more control over combustion than burning raw waste ever allows.
This distinction matters more than it sounds. Feeding solid waste directly into a kiln means dealing with inconsistent moisture, particle size, and composition, all of which can destabilize the flame and the clinker quality. Gasifying that waste first strips out much of that variability, producing a gas with a more predictable calorific value that behaves, from the kiln’s point of view, much closer to a conventional fuel.
Cemex Ventures has backed exactly this approach through its investment in WtEnergy Advanced Solutions, a cleantech startup whose gasification technology converts biomass and non recyclable waste into a lower carbon fuel that can later be upgraded into biomethane or even pure hydrogen. In June 2023, the European Union awarded Cemex and WtEnergy a 4.4 million euro grant to deploy this technology, under the project name CLYNGAS, at Cemex’s cement plant in Alicante, Spain. The European Commission classified CLYNGAS as the first project of its kind in the global cement industry, and the project is expected to avoid roughly 400,000 tons of CO2 equivalent emissions over a decade at that single plant.
For Cemex Ventures, this was never a one-off grant application. WtEnergy has been part of the Cemex Ventures portfolio since an earlier stage, and CLYNGAS represents the natural next step of that relationship: taking a startup’s technology out of the lab and putting it to work inside a live, EMEAA wide cement operation, with an explicit rollout plan across Spain and other regions once the Alicante plant proves the concept.
(Hydrogen) Enhanced Combustion: A Catalyst, not a Replacement Fuel
Hydrogen enhanced combustion means injecting hydrogen into a kiln’s flame as a combustion catalyst, alongside the main fuel mix, rather than as a full substitute for it. The hydrogen itself emits zero CO2 when it burns, and because it ignites more readily than solid alternative fuels, it stabilizes the flame even as the plant increases the share of lower calorific alternative fuels in the mix. In practice, this means a kiln can push its thermal substitution rate significantly higher without the flame instability that would otherwise limit how much alternative fuel it can safely burn.
Cemex has more history with this specific lever than almost any other producer in the sector. The company ran its first hydrogen injection trial at its Alicante plant in July 2019, and by early 2021 it had rolled relevant technology out across its European footprint. Cemex has reported that hydrogen injection increases alternative fuel substitution by roughly eight to ten percentage points at each site where it is deployed, a meaningful jump for a lever that requires no rebuild of the kiln itself. The rollout later extended to four plants in Mexico and to a plant in the Dominican Republic, making Cemex, by its own account, the first major cement producer to commit to hydrogen combustion beyond a pilot.
Cemex has also explored a different technological pathway to scale up hydrogen injection at its plants. . Cemex Ventures made its first investment in HiiROC, a UK– based hydrogen production startup, in 2021, and increased that stake in December 2023 alongside other leading industry players including Centrica, Hyundai, and Kia. HiiROC’s proprietary process, called thermal plasma electrolysis, splits methane, whether from biomethane, flare gas, or natural gas, into hydrogen and a solid, inert by product called carbon black, without the CO2 footprint of conventional steam methane reforming and without the heavy energy demands of water electrolysis. In November 2024, Cemex and HiiROC advanced their partnership with plans to explore the deployment of HiiROC’s technology at Cemex’s Rugby cement plant in the United Kingdom, aiming to increase hydrogen injection capacity well beyond what earlier trials achieved.
The abovementioned also illustrates something important about how this type of deployments could work in practice. According to reporting from The Chemical Engineer, Rugby and other host sites will not become fully hydrogen fueled plants overnight. Instead, HiiROC’s modular, containerized units are designed to be plugged directly into the existing kiln setup, with a new burner enabling hydrogen to be combusted alongside the plant’s existing fuel mix. The engineering goal is to find a sweet spot where hydrogen input levels allow operators to push the limits gradually, by increasing their use of lower calorific alternative fuels without sacrificing flame stability.
Low-Carbon Hydrogen Production: Closing the Loop from Waste to Fuel
Low-carbon hydrogen production refers to any method of producing hydrogen that avoids, or largely avoids, the carbon emissions associated with the conventional route, Steam Methane Reforming (SMR), which strips hydrogen from natural gas while releasing CO2 in the process. The industry commonly separates hydrogen by color: grey hydrogen comes from unabated fossil gas, blue hydrogen pairs that same process with carbon capture, and green hydrogen comes from renewable electricity powering water electrolysis. Waste– to– hydrogen technologies, which represents another pathway Cemex is exploring, occupy an increasingly important fourth category: producing hydrogen directly from biogenic or non-recyclable waste streams that would otherwise be landfilled or incinerated.
This is precisely the gap that the HYIELD project is designed to address. In late 2023, the the project was awarded a 10 million euro grant through the European Union’s Horizon Europe programme, under the Clean Hydrogen Partnership, as part of a sixteen member consortium, including Cemex, WtEnergy Advanced Solutions, H2Site, Veolia, Enagás, ArcelorMittal, and several research institutes, to build what the consortium describes as Europe’s first industrial scale waste to hydrogen demonstration plant. The plant will combine WtEnergy’s gasification technology, the same CleanTech process behind CLYNGAS, with a membrane separation reactor from H2Site to purify the resulting syngas into hydrogen exceeding 99.97% purity. Over the course of the four-year project, the facility is expected to process more than 2,000 tons of waste and produce nearly 400 tons of green hydrogen, hosted at Cemex’s cement factory in Alcanar, Spain.
What makes HYIELD worth watching from an investment standpoint is not just the grant size, but what they enable WtEnergy to demonstrate. The project builds on , WtEnergy’s gasification platform to convert waste into a low-carbon synthesis gas that can be further upgraded into valuable and clean hydrogen. The combination of public funding and WtEnergy’s existing technology platform provides an opportunity to demonstrate how waste-derived syngas can contribute to the decarbonization of hard-to-abate industrial sectors, while potentially opening up additional applications across the fuel value chain.
How Gasification, Enhanced Combustion, and Low-Carbon Hydrogen Production Reinforce Each Other
It helps to think of these three levers as stages of the same value chain rather than three competing options. Gasification turns waste into a usable gas. That gas can either be burned as an alternative fuel on its own or upgraded into pure hydrogen through a project like HYIELD; similarly, hydrogen– enhanced combustion systems like HiiROC will show substantial benefits at a steady pace. In each case, the underlying goal is the same: raise the thermal substitution rate as high as physically possible, while keeping the kiln stable and the clinker quality consistent.
This is also why Cemex’s approach across CLYNGAS, HYIELD, and HiiROC does not look like three unrelated pilot projects scattered across Europe. It looks like a company building the fuel infrastructure of a low carbon kiln piece by piece, starting with the direct transformation of fuel itself (gasification), moving to how new fuels are used to stabilize combustion (hydrogen– enhanced combustion), and finally closing the loop by introducing novel and cleaner streams to further decarbonize current fuel mixes.
Why This Matters for Investors and for the Built World
For a cement producer, fuel transition is one of the few decarbonization levers that pays for itself relatively quickly. Alternative fuels are, in most markets, cheaper than coal or petroleum coke, and raising a plant’s thermal substitution rate is a direct cost reduction as much as an emissions reduction. That is part of why the Global Cement and Concrete Association treats fuel switching as one of the most mature, most immediately deployable levers in its net zero roadmap, well ahead of technologies like carbon capture that still require significant infrastructure to scale.
For Cemex Ventures, that economic logic is exactly why fuel transition has attracted sustained, multi-year investment rather than a single headline deal. WtEnergy and HiiROC are not names that appeared once in a press release and disappeared. They are portfolio companies whose technologiesy have continued to progress through successive stages of development and collaboration with Cemex. That is the pattern Cemex Ventures looks for across its portfolio: not a single breakthrough, but a startup whose technology keeps proving itself at the next scale up, inside a real cement plant with real production targets.
As the sector moves further into its Future in Action program and toward net zero CO2 by 2050, expect fuel transition to keep occupying an outsized share of the conversation, not because it is the most dramatic technology on the table, but because it is one of the few that is already working, at scale, today.
Beyond Three Levers: An Open Door to Electrification
Waste gasification, hydrogen-enhanced combustion, and low-carbon hydrogen production are the three fuel transition pathways where Cemex has built the deepest track record so far, but they are not meant to be the final word. Decarbonizing kiln heat is a challenge with more than one possible answer, and the sector is still early in discovering which combinations will work best for each market, each plant, and each local fuel supply.
Electrification is one of the most promising of those alternative routes. Technologies that generate high-temperature process heat from electricity, such as plasma or resistive heating, or thermal energy storage charged with renewable power, could open a path to producing clinker with far less dependence on combustion altogether. Many of these solutions are still at pilot or demonstration stage, and their viability will hinge on access to abundant, affordable clean power. That, however, is exactly the kind of early-stage challenge where a corporate venture capital arm can add real value: providing capital, industrial know-how, and live plants where new ideas can be tested.
That is why Cemex Ventures remains open to exploring pathways beyond the ones described here. If you are a founder working on electrified kiln heat, or on any other technology that can help cement plants move away from fossil fuels, we want to hear from you. The fuel transition is already underway, and its next breakthroughs may well come from places the industry is only beginning to look.
