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Yes, but only for the energy-related part of a cement plant’s emissions. A waste-heat recovery system can use heat rejected by the kiln, preheater and clinker cooler to generate electricity or useful heat. If that net energy displaces purchased electricity or fuel with a higher emissions intensity, the plant’s indirect emissions fall. The system does not stop the carbon dioxide released when limestone is chemically converted into clinker, so it is an efficiency measure rather than a complete cement-decarbonization solution.
The size of the reduction depends on measured net energy delivery, the emissions factor of the electricity or fuel displaced, parasitic loads, operating hours and the way the equipment is integrated with the kiln. Published project figures describe particular plants and assumptions, not a universal percentage reduction for every cement works.
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Which cement-plant emissions can waste-heat recovery affect?
Calcination creates process emissions
Portland cement clinker is made by heating limestone and other raw materials to very high temperatures. During calcination, the carbon-containing mineral calcium carbonate is chemically converted into calcium oxide, releasing carbon dioxide. That gas is a process emission: it comes from the raw material transformation, not from the electricity used by fans or the fuel burned in the kiln.
Recovering heat from an exhaust stream does not reverse or prevent this chemical reaction. A kiln still has to calcine its feed, and the associated process CO2 remains unless the plant changes its raw materials, clinker chemistry or uses carbon capture, utilization and storage.
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Energy use creates a second emissions stream
Cement plants also consume energy for kiln firing, material handling, fans, grinding, pumps and other equipment. Purchased electricity carries the emissions intensity of the local grid. On-site fuel produces direct combustion emissions. If recovered heat supplies electricity or useful thermal energy that would otherwise have been purchased, the plant can avoid those energy-related emissions.
The correct question is therefore not whether the recovery equipment makes the kiln’s exhaust disappear. It is whether the system delivers enough net useful energy to displace a more emissions-intensive source after accounting for the electricity and fuel consumed by the recovery equipment itself.
How a cement kiln waste-heat recovery system works
Steam-cycle systems using boilers and a turbine
One established arrangement routes suitable exhaust through waste-heat boilers. The clinker cooler outlet is commonly connected to an air-quenching cooler (AQC) boiler, while preheater or kiln-inlet exhaust is connected to a suspension-preheater (SP) boiler. The boilers produce steam, and a turbine-generator converts that steam into electricity.
UNIDO’s 2007 Chinese cement-sector energy-efficiency report describes projects using AQC and SP boilers with a condensing turbine-generator. The exact boiler arrangement, steam conditions, ducting and turbine size are engineering decisions for the individual kiln line; the report’s configurations are project examples rather than a universal design prescription.
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Good integration protects kiln availability. The same report describes bypass exhaust piping so kiln operation can continue if a boiler or the power station is unavailable. Without a safe bypass, a fault in the recovery plant could become a constraint on clinker production rather than simply a loss of recovered power.
Direct thermoelectric generation
A different approach is a thermoelectric generator (TEG). Instead of producing steam first, thermoelectric cartridges convert a temperature difference directly into electricity. The U.S. Department of Energy’s validation program at Amrize’s Alpena plant in Michigan reported pilot-scale results for this type of system in 2025.
DOE reported 3.1 kWh of gross generation per tonne of clinker and 2.0 kWh per tonne of net generation after parasitic loads. It also reported 5.0% peak system thermal efficiency and 4.3% average system thermal efficiency. Those system figures should not be confused with the efficiency of individual cartridges, which DOE reports separately.
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The following figures illustrate the range of reported project data. They should not be treated as industry-wide averages.
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| Project or system | Reported capacity or output | Operating context | Source and qualification |
|---|---|---|---|
| Amrize Alpena thermoelectric pilot | 3.1 kWh gross per tonne of clinker; 2.0 kWh net per tonne | 5.0% peak and 4.3% average system thermal efficiency | U.S. Department of Energy validation page, published August 5, 2025; pilot-scale results |
| Typical plant projection based on the Alpena pilot | $241,000 annual electricity savings | Plant producing 3,300 tonnes of clinker per day; electricity priced at $0.10/kWh in the stated assumptions | DOE projection, not measured annual savings at the Alpena host |
| Shanghai Wanan Group Jinshan Cement Plant example | 2.5 MW installed; 1.9–2.1 MW normal generation | 1,200-tonne-per-day clinker line operating from 2003 | UNIDO project report, 2007; historical project data |
| Separate UNIDO project design | 3 MW installed capacity | Two waste-heat boilers with a condensing turbine-generator | UNIDO project report, 2007; design example |
The difference between gross and net output is central to interpreting these numbers. Gross generation is the electricity produced before equipment loads. Net generation is what remains available to offset purchased power after pumps, fans, controls and other parasitic demands have been supplied. Emissions calculations should use the latter.
When does recovered energy produce a real emissions reduction?
A plant-specific estimate should compare avoided emissions with the emissions and energy use attributable to operating the recovery system. In practical terms:
Net emissions avoided = (net useful energy delivered × emissions factor of displaced energy) − emissions associated with recovery-system operation
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsThe calculation requires four measured or documented inputs:
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- Baseline: the electricity or fuel the plant would have used without recovery.
- Net delivered energy: electricity or useful heat available after parasitic loads.
- Displaced-energy emissions factor: the grid factor for purchased electricity or the factor for the fuel and thermal service being replaced.
- Operating conditions: clinker throughput, exhaust temperature and flow, availability, seasonal operation and maintenance downtime.
A system can have impressive gross output but a smaller climate benefit if its fans, pumps or cooling equipment consume a substantial share of generation. Conversely, a modest net output can avoid meaningful emissions where the displaced grid electricity is carbon-intensive. The same equipment may deliver a different result after a plant changes its electricity supply, fuel mix or production schedule.
Why waste-heat recovery does not solve cement’s full CO2 problem
The International Energy Agency’s 2023 cement guide explains that emissions cuts are difficult because cement production depends on carbon-containing raw materials and high-temperature heating. It identifies energy and material efficiency and lower-emissions fuels as near-term measures. Deeper reductions require measures such as alternative raw materials and carbon capture, utilization and storage.
Waste-heat recovery addresses energy efficiency. It can reduce the electricity or useful heat that must be purchased, but it does not remove the CO2 released during limestone calcination. A credible plant decarbonization plan therefore tracks recovery alongside clinker substitution, supplementary cementitious materials, alternative fuels, process changes and, where appropriate, carbon capture.
The IEA’s 2025 Breakthrough Agenda Report adds important sector context: total cement CO2 emissions were higher than in 2015, while direct emissions intensity had remained unchanged in recent years. The report associates recent overall reductions with lower global production and identifies material efficiency, alternative fuels, supplementary cementitious materials and carbon capture and storage among transition measures. Those observations describe the sector; they are not a measured performance result for any one waste-heat installation.
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Choosing between steam-cycle and thermoelectric recovery
Both approaches can turn kiln heat into electricity, but they present different engineering questions. A steam-cycle plant needs boilers, steam equipment, a turbine-generator, water systems and controls. A thermoelectric system uses heat-transfer surfaces and generator cartridges, avoiding the steam loop but depending on temperature gradients, module performance and thermal integration.
| Decision axis | Steam-cycle boilers and turbine-generator | Thermoelectric generation |
|---|---|---|
| Heat source | Suitable preheater and clinker-cooler exhaust routed through boilers | Heat transferred across thermoelectric cartridges |
| Output metric | Assess net turbine electricity after pumps, fans and auxiliaries | Assess net electricity; DOE’s pilot reports both gross and net output |
| Kiln continuity | Bypass exhaust piping can allow kiln operation during boiler or power-station failure in the UNIDO examples | Requires a plant-specific safe operating and bypass strategy |
| Efficiency evidence reported | Project capacities are documented, but no universal efficiency is established | DOE reports 5.0% peak and 4.3% average system thermal efficiency for its pilot |
| Cost and maintenance comparison | Requires a site-specific installed-cost and maintenance assessment | Requires a site-specific installed-cost and maintenance assessment |
The available project descriptions do not provide a controlled head-to-head test or a complete lifecycle-cost comparison. Selection should follow the heat-source survey, required availability, water and space constraints, maintenance capability and the value of the electricity or heat displaced.
How to assess a project at an individual cement plant
- Map the heat sources. Measure temperature, flow, dust loading and operating variability at the preheater outlet, kiln inlet and clinker cooler outlet. Record conditions at different production rates rather than relying on a single design point.
- Establish the energy baseline. Meter purchased electricity and relevant fuel or thermal services. Separate kiln, cooler, grinding and auxiliary loads so the displaced service is unambiguous.
- Model net output. Estimate boiler, turbine, thermoelectric, pump, fan, cooling and control loads. Report gross and net generation separately.
- Apply the correct emissions factor. Use the factor for the actual grid or fuel being displaced, with its geography, date and accounting boundary documented.
- Check kiln integration. Verify duct pressure, dust management, temperature limits, maintenance access and a bypass route that preserves safe kiln operation if recovery equipment trips.
- Test availability assumptions. Include planned shutdowns, raw-material interruptions, cooler conditions, seasonal operation and degradation. A nameplate capacity is not the same as annual net generation.
- Verify the result after commissioning. Use calibrated meters to compare recovered net energy with the baseline and update the emissions calculation using actual operating data.
Common interpretation mistakes
- Using gross output as the climate benefit: auxiliaries consume power, so net generation is the relevant displacement figure.
- Calling all kiln CO2 avoidable through recovery: calcination emissions remain unless a separate process or capture measure addresses them.
- Generalizing one project: the UNIDO capacities are historical examples, and the DOE figures come from a pilot and a stated projection.
- Assuming savings equal emissions reductions: a dollar estimate depends on electricity price; an emissions estimate depends on the displaced energy’s emissions factor.
- Ignoring reliability: recovery equipment must be integrated so a boiler, turbine or generator fault does not force an unsafe or unnecessary kiln stoppage.
Bottom line for cement-plant owners
Waste-heat recovery can reduce a cement plant’s energy-related emissions when its measured net electricity or useful heat displaces more emissions-intensive purchased energy. The technology is technically established in steam-cycle projects, and thermoelectric generation is being demonstrated at pilot scale. Its climate value is plant-specific: it depends on recoverable heat, net output, parasitic consumption, operating availability and the emissions intensity of the displaced energy.
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It should be evaluated as one layer of a broader cement strategy. Recovery can lower indirect energy emissions, but it does not eliminate limestone-calcination CO2, so it cannot by itself deliver deep decarbonization of clinker production.
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