Concrete

Concrete as a Carbon Sink for Reducing Global Warming

Published

2 years ago

March 19, 2024

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Dr Anjan K Chatterjee, Managing Director, Conmat Technologies, Kolkata, presents a comprehensive analysis of the intricate dynamics of the carbon cycle and its implications for global climate change, particularly focusing on the role of the cement and concrete industry. Examining the interplay between carbon sources and sinks, he explores the potential of concrete as a carbon sink, shedding light on its carbonation process and the implications for CO2 sequestration, in the first instalment of this two-part series.

The ‘Carbon Cycle’ that interconnects the natural carbon sources and carbon sinks is a critical life-support process in our planet (Figure 1). The most abundant greenhouse gas, carbon dioxide (CO2), is continuously recycled on the earth. Carbon sources refer to the processes that release CO2 to the atmosphere, while carbon sinks are the processes that absorb it. As we know, forests, soil, oceans, the atmosphere, and fossil fuels are the important stores of carbon and it moves between these different stores that act either as sinks or sources. It is also understood that a sink absorbs more carbon than it gives off, while a source emits more carbon than it absorbs. The amount of carbon in the atmosphere at any time depends on the balance that exists between the sinks and sources.

Figure 1: Carbon sources and sinks constituting the carbon cycles

Before the Industrial Revolution the carbon cycle was relatively balanced but it has been tilted later towards higher concentration of carbon in the atmosphere due to the increasing industrial activities on the planet (Figure 2). This has been happening because humans produce the greenhouse gases (GHG), and more particularly CO2 and CH4 (methane), much faster than the natural sources can absorb them. The production-based global generation of GHG, and the top eight GHG emitting countries in 2018 are shown below:

China: 11,706 MT CO2-e
USA: 5,794
India: 3,347
EU + UK: 3,333
Russia: 1,992
Indonesia: 1,704

Brazil: 1,421
Japan: 1,155
Total World: 48,928
Among the industrial activities, the production of Portland cement ranks high in generating CO2, creating up to 8 per cent of worldwide man-made emissions of this gas. This is identified as a major contributor to the probable rise in average global temperature exceeding 20C. In recent years, a school of thought has emerged whether it is justified to consider the amount of CO2 emitted directly from the cement manufacturing process as the total cement industry emissions to affect the global temperature rise. This is due to the fact that cement is used mainly in the form of concrete, mortar and plaster in built structures, which over time undergo carbonation involving reverse penetration of CO2. The knowledge about carbonation of existing concrete structures is well-established. The CO2 uptake by the cement-based products including concrete has not been considered historically in the CO2 estimation for climate change. Furthermore, there are many technologies in development, which promise significant potential of enhancing the recycling of CO2 in concrete and cement-based products. Thus, it seems justified to consider that, while the cement production is a carbon source, the cement-based products may act as carbon sinks. The concept of concrete as a carbon sink will be a game-changer for the cement and concrete industry as a whole for improving the climate performance of the sector.

Recap of Concrete Carbonation
Carbonation of concrete has been a subject of study primarily for understanding the mechanism of reinforcement corrosion and the resultant deterioration of concrete. In concrete carbonation, the reaction process relates to the cement matrix part of the concrete and its occurrence is eventually inevitable. It is caused by the ingress of atmospheric CO2 reacting with the pore water to form carbonic acid, which in turn reacts with the lime-bearing hydrated phases in the cement matrix.. This neutralises the alkalinity of concrete and occurs progressively. A carbonation front moves through the concrete until it reaches the steel. The passive layer then breaks down as pH falls from over 12.0 to around 8.0. In fact, corrosion of steel starts in the presence of O2 and H2O as pH falls below 11.0.

A typical Portland cement concrete may show a carbonation depth of 5-8 mm after about 10 years, rising to 10-15 mm after 50 years. Therefore, structures with low concrete cover over the reinforcing steel will show carbonation-induced corrosion more quickly than those with good cover. The rate of advancement of the carbonation front is dependent on the diffusion kinetics of CO2 in concrete, which in turn is related to its quality. Concretes made with high w/c ratios and with low cementitious materials content will carbonate faster than low-porosity high-strength concrete. The blended cement concretes, because of their low alkaline reserves, tend to carbonate faster than the grade of concrete for an equivalent OPC content. The rate of carbonation is also affected by the environmental conditions. Carbonation is more rapid in fairly dry and wet-and-dry cyclic environments.
Though carbonation is a harmful process for the reinforcement steel, for the concrete mass without metal reinforcement, the effect is beneficial, because the product of carbonation reaction CaCO3 has larger volume than the major hydrating phase Ca(OH)2, thus resulting in better pore filling and increase in the strength of concrete. It has also been observed that the carbonation reactions occur during the entire life cycle of a structure or a concrete element, though it might be initiated at the exposed surfaces and limited to cover concrete, jointing mortar and plasters and renderings. Interestingly, a study on concrete bridges cast between 11 and 76 years revealed that at 76 years of casting carbonation of concrete was still evident except that the carbonation rate was lower compared to newer structures [1].

Carbonation reaction
It is known that surfaces of concrete and other cement-based materials in direct contact with carbon dioxide and water are prone to carbonation, which spreads inwards at a rate proportional to the square root of time. The hydrated cement phases and the pore solution are the starting points for carbonation. There are four important hydration products with varying amounts of CaO available in them for carbonation as shown in Table 1 [2]. Portlandite (CH) and C-S-H gel are the most abundant in occurrence with high binding capacity.
Carbon dioxide dissolves in the pore solution of cement paste, producing carbonate ions, which react with calcium ions to produce solid calcium carbonate. The hydroxyl and calcium ions required by these reactions are obtained by the dissolution of calcium hydroxide and decomposition of the hydrated silicate and aluminate phases. The reactions involving the calcium hydroxide and calcium silicate hydrate phases may be represented by the following equations:
CO2 + 2OH- ? CO32- + H2O
(1)
Ca2+ + CO32- ? CaCO3 (2)
Ca(OH)2 ? Ca2+ + 2OH- (3)
xCaO.SiO2(aq) + zH2O ? yCa2+ + 2yOH- + (x – y)CaO.SiO2(aq)
(4)
The rate and degree of carbonation is governed mainly by the factors such as the size and geometry of the porous structure, the degree of water saturation in the pore system, the type of cement and supplementary cementitious materials, the chemical composition of the pore solution, the temperature, and the concentration of CO2 in the atmosphere. As already stated above, the carbonation of the hydrated cement matrix results in increase of strength and hardness in concrete and also reduction of its permeability and shrinkage. The concrete becomes more volume stable and consequently, further volume destabilisation due to subsequent moisture changes is prevented.

co2 Uptake in Concrete
The degree of carbonation in concrete is generally determined in the laboratory by the phenolphthalein test. The phenolphthalein applied carbonated periphery in a broken piece of a carbonated concrete is shown in Figure 4.

Figure 4: Carbonated periphery of a crushed concrete fragment as determined by the phenolphthalein test.

It is generally observed that in the first year of service the carbonation depth varies from I mm in dense dry concrete to 5 mm or more in more permeable concrete with high water content. The depth increases in subsequent years. The carbonation process proceeds faster when RH lies in the range of 50-75 per cent.
Calculating the uptake of CO2 in concrete and other cement-containing products as well as its impact on the global climate is a complex task. There is no unambiguous calculation method that can be used for this purpose. However, certain approximate and empirical models were attempted for this purpose and the results were significantly different. A comprehensive summary was published in 2016 [3]. The findings can be broadly summarised as follows:

A study conducted in 2005 in four Nordic studies showed that within 50 years the projected extent of carbonation will range from 24% to 43%. The penetration depth will be about 32 mm.
A 1997 study of 18 bridges, aged from 14 to 56 years at the time of study, reported carbonation depths of up to 50 mm.
A 2017 study of the Itaipu dam commissioned in 1984 in Paraguay reported the average and maximum carbonation depths of 33 mm and 73.3 mm.
A 2018 study of two 100-year old bridges in Slovakia revealed that the exposed surfaces carbonated to a depth of 60 mm, but some surfaces protected by 2-3 mm layers of impermeable plaster prevented carbonation.
The demolished concrete materials showed faster rates of carbonation.

Another study, based on different datasets compiled from field surveys in China and a comprehensive synthesis of prior data, was reported in [4]. The study attempted to model the global atmospheric CO2 uptake not only in concrete but also in mortar, construction cement waste, and cement kiln dust between 1930 and 2013 in four regions, e.g., China, the US, Europe and the rest of the world. Furthermore, the study included a sensitivity analysis of the uptake estimates in respect of 26 different variables. Without going into the details of calculations, it may be stated that for concrete three stages in the lifecycle were considered – service life, demolition and secondary use of concrete waste. In each case the exposed surface areas, thicknesses, exposure conditions including the atmospheric CO2 concentrations in different regions, and exposure time were taken into account in the modelling exercise. The average service life of the buildings was derived from the range of 35 to 70 years. The effects of different strength classes in concrete, exposure conditions, additions and coatings were explicitly modelled. The calculation of carbon sequestration from mortar was calculated from mortar thickness and annual carbonation depth. The carbon uptake in construction waste and kiln dust was calculated with due consideration of the generation rate and measured carbonation fractions. For modelling, Fick’s diffusion law was used and the carbonation rate coefficients were derived from both experimental measurements and review of relevant literature. The net annual CO2 emissions related to cement production minus the estimated annual CO2 sequestration due to carbonation of cement materials is shown in Figure 5. Between 1990 and 2013 the annual carbon uptake has shown an increase 5.8 per cent per year on average, slightly faster than 5.4 per cent growth in process emissions. Cumulatively it was estimated that an amount of 4.5 GtCyr-1 has been sequestered by cement materials since 1930 and more specifically, the annual sequestration rate increased from 0.10GtCyr-1 in 1998 to 0.25 GtCyr-1 in 2013. In total, it was estimated that roughly 43 per cent of the cumulative cement process emissions of CO2 produced between 1930 and 2013 have been reabsorbed by carbonating cement materials.

A few other points that emerged from this study are worth mentioning:

During the period of study, based on the regional details, the break-up of CO2 storage was 68 per cent from concrete, 27 per cent from mortar, 2 per cent from cement losses in the course of construction, and 3 per cent from cement kiln dust
Cement mortars acted as the most effective carbon sink, though only 30 per cent of cement is used in it. This was apparently because of the extensive exposed exterior surface of mortars.
Despite a relatively smaller exposure area, concrete was the second largest contributor to the carbon sink, because of its sheer volume.
The cement losses during construction and the cement kiln dust at the production stage were also contributors to the total sink.

Reporting co2 Emissions
Three international systems for monitoring, quantifying and reporting of CO2 emissions are prevalent:

Reporting of national CO2 emissions to UNFCCC (United Nations Framework Convention on Climate Change)
EU climate and energy frameworks for lowering climate impact
Environmental product declaration (EPD)

The guidelines for UNFCCC reporting were developed by the IPCC (Intergovernmental Panel on Climate Change). Although the carbonation of cement products was included in the document in 2006 but the scientific consensus then was not in favour of inclusion into national inventories. Since it has now emerged from various studies that the concrete as carbon sink must be accounted for in calculating the net emissions of CO2, there is an urgent need to review the IPCC guidelines. The situation is not much different in the EU systems that include ETS (Emission Trading System) and ESR (Effort Sharing Regulation). It appears that there is some flexibility in EU/ESR to consider CO2 bound in construction timber but not for the emissions and uptake by the concrete construction. In EPD, there is a scope for following the European standard EN 16757:2017 (Sustainability of construction works – Environmental Product Declarations – Product Category Rules for Concrete and Concrete Elements), though mortars and renderings are not covered in the standard.
Thus, there is a visible gap in developing a scientifically reliable approach for tracking and reporting of CO2 emissions and absorption in the cement, cement-based building products and concrete construction sectors at the national and international levels.

Modeling approach for calculating CO2 uptake in existing concrete structures
A comprehensive review has been presented in [5]. The emission and uptake model, illustrated by the author, is reproduced in Figure 6. Compared to the emission process, the uptake processes are much slower and longer. The primary uptake is by concrete structures such as bridges, house frames, concrete tiles, concrete roads, railway sleepers, cement mortars, etc. The uptake by the post-demolition secondary products refers to crushed concrete, which may be used in as a road base or for landfilling. A complete CO2 uptake model must consider both the primary and secondary uptakes with different timeframes.
The depth of carbonation, d, can be calculated by the well-established formula: d=kvt, where, t is time and k is the rate of carbonation, depending on the exposure and concrete quality. In addition, it is necessary to know another parameter, DOC (Degree of Carbonation), defined as the amount of CO2 uptake in relation to the theoretical maximum CO2 uptake, corresponding to 100 per cent DOC. While the theoretical maximum uptake can be taken as the amount of CO2 emitted from the limestone calcination in the clinker making process, the degree of carbonation may be determined by the phenolphthalein test on concrete samples. Values of k and DOC are provided in the annexure to EN 16757:2018.
The CO2 uptake in kg per m2 of concrete during t years for any application can be calculated as CO2 uptake at a surface = (k x DOC)(v (t)/1000) x Utcc x C, (5)
Where k is the rate of carbonation for the surface in mm/v(t),
DOC is degree of carbonation for the surface,
T is the number of years, Utcc is the maximum theoretical uptake in kg CO2/kg cement (e.g., ~0.49 for CEM I), C is the cement content in kg cement/m3 concrete.
For an application, structure or product the total CO2 uptake in kg may then be calculated, based on the sum of the uptake at all different surfaces according to the equation

Figure 6: Schematic diagram of the CO2 emission and uptake model.

Total CO2 uptake = S(ki x DOCi x Ai) x Utcc x C (6) where i denotes surfaces and A is the surface area in m2.
Further, the CO2 uptake per m3 can be obtained by dividing the total uptake by the total volume of concrete.
The blended cements or concrete with additions like granulated slag, fly ash or calcined clay are normally considered to have higher carbonation rates but precise and reliable data is not readily available. Hence, a possible way out for the present may be to apply a factor, corresponding to the clinker content in the blended cement, to the theoretical uptake computed for the normal Portland cement such as CEM I.
Further to the above approach of modeling, two other progressively more precise approaches, termed as tier 2 and tier 3, have been proposed in [5], These refined approaches essentially are based on the use of historical cement production and application statistics in a country or a region with varying timeframes. The three tiers will also differ in respect of the uptake parameters at the end-of-life stage and the secondary use stage of concrete. The intent is to have a reliable estimate of net emissions of CO2 from the cement industry after proper accounting of reabsorption of CO2 in concrete and other cement-based building products.

*References will be provided in the concluding part, in the next issue

ABOUT THE AUTHOR
Dr Anjan K Chatterjee is a Fellow at the Indian National Academy of Engineering, a Materials Scientist and the Author of ‘Cement Production Technology: Principles and Practice.’

Table 1: Major hydration products of Portland cement and their binding capacity
Compositional parameters CSH CH AFm AFt All
Hydrate phase content, % 50 25 10 10 95
CaO molar ratio 0.42 0.76 0.36 0.27 –
CaO % corresponding to the hydrate phase content 21 19 3.6 2.7 46
Assumed degree of carbonation, % 50 100 75 50 –
CaO available for carbonation in the hydrate phases, % 11 19 2.7 1.3 34
CaO available for carbonation relative to the total CaO in the hydrate phases, % 23.9 41.3 5.9 2.8 74

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Cement Industry Backs Co-Processing to Tackle Global Waste

Industry bodies recently urged policy support for cement co-processing as waste solution

Published

22 hours ago

January 15, 2026

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Leading industry bodies, including the Global Cement and Concrete Association (GCCA), European Composites Industry Association, International Solid Waste Association – Africa, Mission Possible Partnership and the Global Waste-to-Energy Research and Technology Council, have issued a joint statement highlighting the cement industry’s potential role in addressing the growing global challenge of non-recyclable and non-reusable waste. The organisations have called for stronger policy support to unlock the full potential of cement industry co-processing as a safe, effective and sustainable waste management solution.

Co-processing enables both energy recovery and material recycling by using suitable waste to replace fossil fuels in cement kilns, while simultaneously recycling residual ash into the cement itself. This integrated approach delivers a zero-waste solution, reduces landfill dependence and complements conventional recycling by addressing waste streams that cannot be recycled or are contaminated.

Already recognised across regions including Europe, India, Latin America and North America, co-processing operates under strict regulatory and technical frameworks to ensure high standards of safety, emissions control and transparency.

Commenting on the initiative, Thomas Guillot, Chief Executive of the GCCA, said co-processing offers a circular, community-friendly waste solution but requires effective regulatory frameworks and supportive public policy to scale further. He noted that while some cement kilns already substitute over 90 per cent of their fuel with waste, many regions still lack established practices.

The joint statement urges governments and institutions to formally recognise co-processing within waste policy frameworks, support waste collection and pre-treatment, streamline permitting, count recycled material towards national recycling targets, and provide fiscal incentives that reflect environmental benefits. It also calls for stronger public–private partnerships and international knowledge sharing.

With global waste generation estimated at over 11 billion tonnes annually and uncontrolled municipal waste projected to rise sharply by 2050, the signatories believe co-processing represents a practical and scalable response. With appropriate policy backing, it can help divert waste from landfills, reduce fossil fuel use in cement manufacturing and transform waste into a valuable societal resource.

Concrete

Industry Bodies Call for Wider Use of Cement Co-Processing

Joint statement seeks policy support for sustainable waste management

Published

2 days ago

January 14, 2026

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Leading industry organisations have called for stronger policy support to accelerate the adoption of cement industry co-processing as a sustainable solution for managing non-recyclable and non-reusable waste. In a joint statement, bodies including the Global Cement and Concrete Association, European Composites Industry Association, International Solid Waste Association – Africa, Mission Possible Partnership and the Global Waste-to-Energy Research and Technology Council highlighted the role co-processing can play in addressing the growing global waste challenge.

Co-processing enables the use of waste as an alternative to fossil fuels in cement kilns, while residual ash is incorporated into cementitious materials, resulting in a zero-waste process. The approach supports both energy recovery and material recycling, complements conventional recycling systems and reduces reliance on landfill infrastructure. It is primarily applied to waste streams that are contaminated or unsuitable for recycling.

The organisations noted that co-processing is already recognised in regions such as Europe, India, Latin America and North America, operating under regulated frameworks to ensure safety, emissions control and transparency. However, adoption remains uneven globally, with some plants achieving over 90 per cent fuel substitution while others lack enabling policies.

The statement urged governments and institutions to formally recognise co-processing in waste management frameworks, streamline environmental permitting, incentivise waste collection and pre-treatment, account for recycled material content in national targets, and support public-private partnerships. The call comes amid rising global waste volumes, which are estimated at over 11 billion tonnes annually, with unmanaged waste contributing to greenhouse gas emissions, pollution and health risks.

Concrete

Why Cement Needs CCUS

Published

3 days ago

January 13, 2026

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Cement’s deep decarbonisation cannot be achieved through efficiency and fuel switching alone, making CCUS essential to address unavoidable process emissions from calcination. ICR explores if with the right mix of policy support, shared infrastructure, and phased scale-up from pilots to clusters, CCUS can enable India’s cement industry to align growth with its net-zero ambitions.

Cement underpins modern development—from housing and transport to renewable energy infrastructure—but it is also one of the world’s most carbon-intensive materials, with global production of around 4 billion tonnes per year accounting for 7 to 8 per cent of global CO2 emissions, according to the GCCA. What makes cement uniquely hard to abate is that 60 to 65 per cent of its emissions arise from limestone calcination, a chemical process that releases CO2 irrespective of the energy source used; the IPCC Sixth Assessment Report (AR6) therefore classifies cement as a hard-to-abate sector, noting that even fully renewable-powered kilns would continue to emit significant process emissions. While the industry has achieved substantial reductions over the past two decades through energy efficiency, alternative fuels and clinker substitution using fly ash, slag, and calcined clays, studies including the IEA Net Zero Roadmap and GCCA decarbonisation pathways show these levers can deliver only 50 to 60 per cent emissions reduction before reaching technical and material limits, leaving Carbon Capture, Utilisation and Storage (CCUS) as the only scalable and durable option to address remaining calcination emissions—an intervention the IPCC estimates will deliver nearly two-thirds of cumulative cement-sector emission reductions globally by mid-century, making CCUS a central pillar of any credible net-zero cement pathway.

Process emissions vs energy emissions
Cement’s carbon footprint is distinct from many other industries because it stems from two sources: energy emissions and process emissions. Energy emissions arise from burning fuels to heat kilns to around 1,450°C and account for roughly 35 to 40 per cent of total cement CO2 emissions, according to the International Energy Agency (IEA). These can be progressively reduced through efficiency improvements, alternative fuels such as biomass and RDF, and electrification supported by renewable power. Over the past two decades, such measures have delivered measurable gains, with global average thermal energy intensity in cement production falling by nearly 20 per cent since 2000, as reported by the IEA and GCCA.
The larger and more intractable challenge lies in process emissions, which make up approximately 60 per cent to 65 per cent of cement’s total CO2 output. These emissions are released during calcination, when limestone (CaCO3) is converted into lime (CaO), inherently emitting CO2 regardless of fuel choice or energy efficiency—a reality underscored by the IPCC Sixth Assessment Report (AR6). Even aggressive clinker substitution using fly ash, slag, or calcined clays is constrained by material availability and performance requirements, typically delivering 20 to 40 per cent emissions reduction at best, as outlined in the GCCA–TERI India Cement Roadmap and IEA Net Zero Scenario. This structural split explains why cement is classified as a hard-to-abate sector and why incremental improvements alone are insufficient; as energy emissions decline, process emissions will dominate, making Carbon Capture, Utilisation and Storage (CCUS) a critical intervention to intercept residual CO2 and keep the sector’s net-zero ambitions within reach.

Where CCUS stands today
Globally, CCUS in cement is moving from concept to early industrial reality, led by Europe and North America, with the IEA noting that cement accounts for nearly 40 per cent of planned CCUS projects in heavy industry, reflecting limited alternatives for deep decarbonisation; a flagship example is Heidelberg Materials’ Brevik CCS project in Norway, commissioned in 2025, designed to capture about 400,000 tonnes of CO2 annually—nearly half the plant’s emissions—with permanent offshore storage via the Northern Lights infrastructure (Reuters, Heidelberg Materials), alongside progress at projects in the UK, Belgium, and the US such as Padeswood, Lixhe (LEILAC), and Ste. Genevieve, all enabled by strong policy support, public funding, and shared transport-and-storage infrastructure.
These experiences show that CCUS scales fastest when policy support, infrastructure availability, and risk-sharing mechanisms align, with Europe bridging the viability gap through EU ETS allowances, Innovation Fund grants, and CO2 hubs despite capture costs remaining high at US$ 80-150 per tonne of CO2 (IEA, GCCA); India, by contrast, is at an early readiness stage but gaining momentum through five cement-sector CCU testbeds launched by the Department of Science and Technology (DST) under academia–industry public–private partnerships involving IITs and producers such as JSW Cement, Dalmia Cement, and JK Cement, targeting 1-2 tonnes of CO2 per day to validate performance under Indian conditions (ETInfra, DST), with the GCCA–TERI India Roadmap identifying the current phase as a foundation-building decade essential for achieving net-zero by 2070.
Amit Banka, Founder and CEO, WeNaturalists, says “Carbon literacy means more than understanding that CO2 harms the climate. It means cement professionals grasping why their specific plant’s emissions profile matters, how different CCUS technologies trade off between energy consumption and capture rates, where utilisation opportunities align with their operational reality, and what governance frameworks ensure verified, permanent carbon sequestration. Cement manufacturing contributes approximately 8 per cent of global carbon emissions. Addressing this requires professionals who understand CCUS deeply enough to make capital decisions, troubleshoot implementation challenges, and convince boards to invest substantial capital.”

Technology pathways for cement
Cement CCUS encompasses a range of technologies, from conventional post-combustion solvent-based systems to process-integrated solutions that directly target calcination, each with different energy requirements, retrofit complexity, and cost profiles. The most mature option remains amine-based post-combustion capture, already deployed at industrial scale and favoured for early cement projects because it can be retrofitted to existing flue-gas streams; however, capture costs typically range from US$ 60-120 per tonne of CO2, depending on CO2 concentration, plant layout, and energy integration.
Lovish Ahuja, Chief Sustainability Officer, Dalmia Cement (Bharat), says, “CCUS in Indian cement can be viewed through two complementary lenses. If technological innovation, enabling policies, and societal acceptance fail to translate ambition into action, CCUS risks becoming a significant and unavoidable compliance cost for hard-to-abate sectors such as cement, steel, and aluminium. However, if global commitments under the Paris Agreement and national targets—most notably India’s Net Zero 2070 pledge—are implemented at scale through sustained policy and industry action, CCUS shifts from a future liability to a strategic opportunity. In that scenario, it becomes a platform for technological leadership, long-term competitiveness, and systemic decarbonisation rather than merely a regulatory burden.”
“Accelerating CCUS adoption cannot hinge on a single policy lever; it demands a coordinated ecosystem approach. This includes mission-mode governance, alignment across ministries, and a mix of enabling instruments such as viability gap funding, concessional and ESG-linked finance, tax incentives, and support for R&D, infrastructure, and access to geological storage. Importantly, while cement is largely a regional commodity with limited exportability due to its low value-to-weight ratio, CCUS innovation itself can become a globally competitive export. By developing, piloting, and scaling cost-effective CCUS solutions domestically, India can not only decarbonise its own cement industry but also position itself as a supplier of affordable CCUS technologies and services to cement markets worldwide,” he adds.
Process-centric approaches seek to reduce the energy penalty associated with solvent regeneration by altering where and how CO2 is separated. Technologies such as LEILAC/Calix, which uses indirect calcination to produce a high-purity CO2 stream, are scaling toward a ~100,000 tCO2 per year demonstrator (LEILAC-2) following successful pilots, while calcium looping leverages limestone chemistry to achieve theoretical capture efficiencies above 90 per cent, albeit still at pilot and demonstration stages requiring careful integration. Other emerging routes—including oxy-fuel combustion, membrane separation, solid sorbents, and cryogenic or hybrid systems—offer varying trade-offs between purity, energy use, and retrofit complexity; taken together, recent studies suggest that no single technology fits all plants, making a multi-technology, site-specific approach the most realistic pathway for scaling CCUS across the cement sector.
Yash Agarwal, Co-Founder, Carbonetics Carbon Capture, says, “We are fully focused on CCUS, and for us, a running plant is a profitable plant. What we have done is created digital twins that allow operators to simulate and resolve specific problems in record time. In a conventional setup, when an issue arises, plants often have to shut down operations and bring in expert consultants. What we offer instead is on-the-fly consulting. As soon as a problem is detected, the system automatically provides a set of potential solutions that can be tested on a running plant. This approach ensures that plant shutdowns are avoided and production is not impacted.”

The economics of CCUS
Carbon Capture, Utilisation and Storage (CCUS) remains one of the toughest economic hurdles in cement decarbonisation, with the IEA estimating capture costs of US$ 80-150 per tonne of CO2, and full-system costs raising cement production by US$ 30-60 per tonne, potentially increasing prices by 20 to 40 per cent without policy support—an untenable burden for a low-margin, price-sensitive industry like India’s.
Global experience shows CCUS advances beyond pilots only when the viability gap is bridged through strong policy mechanisms such as EU ETS allowances, Innovation Fund grants, and carbon Contracts for Difference (CfDs), yet even in Europe few projects have reached final investment decision (GCCA); India’s lack of a dedicated CCUS financing framework leaves projects reliant on R&D grants and balance sheets, reinforcing the IEA Net Zero Roadmap conclusion that carbon markets, green public procurement, and viability gap funding are essential to spread costs across producers, policymakers, and end users and prevent CCUS from remaining confined to demonstrations well into the 2030s.

Utilisation or storage
Carbon utilisation pathways are often the first entry point for CCUS in cement because they offer near-term revenue potential and lower infrastructure complexity. The International Energy Agency (IEA) estimates that current utilisation routes—such as concrete curing, mineralisation into aggregates, precipitated calcium carbonate (PCC), and limited chemical conversion—can realistically absorb only 5 per cent to 10 per cent of captured CO2 at a typical cement plant. In India, utilisation is particularly attractive for early pilots as it avoids the immediate need for pipelines, injection wells, and long-term liability frameworks. Accordingly, Department of Science and Technology (DST)–supported cement CCU testbeds are already demonstrating mineralisation and CO2-cured concrete applications at 1–2 tonnes of CO2 per day, validating performance, durability, and operability under Indian conditions.
However, utilisation faces hard limits of scale and permanence. India’s cement sector emits over 200 million tonnes of CO2 annually (GCCA), far exceeding the absorptive capacity of domestic utilisation markets, while many pathways—especially fuels and chemicals—are energy-intensive and dependent on costly renewable power and green hydrogen. The IPCC Sixth Assessment Report (AR6) cautions that most CCU routes do not guarantee permanent storage unless CO2 is mineralised or locked into long-lived materials, making geological storage indispensable for deep decarbonisation. India has credible storage potential in deep saline aquifers, depleted oil and gas fields, and basalt formations such as the Deccan Traps (NITI Aayog, IEA), and hub-based models—where multiple plants share transport and storage infrastructure—can reduce costs and improve bankability, as seen in Norway’s Northern Lights project. The pragmatic pathway for India is therefore a dual-track approach: utilise CO2 where it is economical and store it where permanence and scale are unavoidable, enabling early learning while building the backbone for net-zero cement.

Policy, infrastructure and clusters
Scaling CCUS in the cement sector hinges on policy certainty, shared infrastructure, and coordinated cluster development, rather than isolated plant-level action. The IEA notes that over 70 per cent of advanced industrial CCUS projects globally rely on strong government intervention—through carbon pricing, capital grants, tax credits, and long-term offtake guarantees—with Europe’s EU ETS, Innovation Fund, and carbon Contracts for Difference (CfDs) proving decisive in advancing projects like Brevik CCS. In contrast, India lacks a dedicated CCUS policy framework, rendering capture costs of USD 80–150 per tonne of CO2 economically prohibitive without state support (IEA, GCCA), a gap the GCCA–TERI India Cement Roadmap highlights can be bridged through carbon markets, viability gap funding, and green public procurement.
Milan R Trivedi, Vice President, Shree Digvijay Cement, says, “CCUS represents both an unavoidable near-term compliance cost and a long-term strategic opportunity for Indian cement producers. While current capture costs of US$ 100-150 per tonne of CO2 strain margins and necessitate upfront retrofit investments driven by emerging mandates and NDCs, effective policy support—particularly a robust, long-term carbon pricing mechanism with tradable credits under frameworks like India’s Carbon Credit Trading Scheme (CCTS)—can de-risk capital deployment and convert CCUS into a competitive advantage. With such enablers in place, CCUS can unlock 10 per cent to 20 per cent green price premiums, strengthen ESG positioning, and allow Indian cement to compete in global low-carbon markets under regimes such as the EU CBAM, North America’s buy-clean policies, and Middle Eastern green procurement, transforming compliance into export-led leadership.”
Equally critical is cluster-based CO2 transport and storage infrastructure, which can reduce unit costs by 30 to 50 per cent compared to standalone projects (IEA, Clean Energy Ministerial); recognising this, the DST has launched five CCU testbeds under academia–industry public–private partnerships, while NITI Aayog works toward a national CCUS mission focused on hubs and regional planning. Global precedents—from Norway’s Northern Lights to the UK’s HyNet and East Coast clusters—demonstrate that CCUS scales fastest when governments plan infrastructure at a regional level, making cluster-led development, backed by early public investment, the decisive enabler for India to move CCUS from isolated pilots to a scalable industrial solution.
Paul Baruya, Director of Strategy and Sustainability, FutureCoal, says, “Cement is a foundational material with a fundamental climate challenge: process emissions that cannot be eliminated through clean energy alone. The IPCC is clear that in the absence of a near-term replacement of Portland cement chemistry, CCS is essential to address the majority of clinker-related emissions. With global cement production at around 4 gigatonnes (Gt) and still growing, cement decarbonisation is not a niche undertaking, it is a large-scale industrial transition.”

From pilots to practice
Moving CCUS in cement from pilots to practice requires a sequenced roadmap aligning technology maturity, infrastructure development, and policy support: the IEA estimates that achieving net zero will require CCUS to scale from less than 1 Mt of CO2 captured today to over 1.2 Gt annually by 2050, while the GCCA Net Zero Roadmap projects CCUS contributing 30 per cent to 40 per cent of total cement-sector emissions reductions by mid-century, alongside efficiency, alternative fuels, and clinker substitution.
MM Rathi, Joint President – Power Plants, Shree Cement, says, “The Indian cement sector is currently at a pilot to early demonstration stage of CCUS readiness. A few companies have initiated small-scale pilots focused on capturing CO2 from kiln flue gases and exploring utilisation routes such as mineralisation and concrete curing. CCUS has not yet reached commercial integration due to high capture costs (US$ 80-150 per tonne of CO2), lack of transport and storage infrastructure, limited access to storage sites, and absence of long-term policy incentives. While Europe and North America have begun early commercial deployment, large-scale CCUS adoption in India is more realistically expected post-2035, subject to enabling infrastructure and policy frameworks.”
Early pilots—such as India’s DST-backed CCU testbeds and Europe’s first commercial-scale plants—serve as learning platforms to validate integration, costs, and operational reliability, but large-scale deployment will depend on cluster-based scale-up, as emphasised by the IPCC AR6, which highlights the need for early CO2 transport and storage planning to avoid long-term emissions lock-in. For India, the GCCA–TERI India Roadmap identifies CCUS as indispensable for achieving net-zero by 2070, following a pragmatic pathway: pilot today to build confidence, cluster in the 2030s to reduce costs, and institutionalise CCUS by mid-century so that low-carbon cement becomes the default, not a niche, in the country’s infrastructure growth.

Conclusion
Cement will remain indispensable to India’s development, but its long-term viability hinges on addressing its hardest emissions challenge—process CO2 from calcination—which efficiency gains, alternative fuels, and clinker substitution alone cannot eliminate; global evidence from the IPCC, IEA, and GCCA confirms that Carbon Capture, Utilisation and Storage (CCUS) is the only scalable pathway capable of delivering the depth of reduction required for net zero. With early commercial projects emerging in Europe and structured pilots underway in India, CCUS has moved beyond theory into a decisive decade where learning, localisation, and integration will shape outcomes; however, success will depend less on technology availability and more on collective execution, including coordinated policy frameworks, shared transport and storage infrastructure, robust carbon markets, and carbon-literate capabilities.
For India, a deliberate transition from pilots to practice—anchored in cluster-based deployment, supported by public–private partnerships, and aligned with national development and climate goals—can transform CCUS from a high-cost intervention into a mainstream industrial solution, enabling the cement sector to keep building the nation while sharply reducing its climate footprint.

– Kanika Mathur