top of page
  • Duncan McLachlan

Implementing Cement CCUS

Updated: Jul 9

As published in Global Cement Magazine's July - August 2024 issue focussed on CCUS with articles on the future EU Emissions Trading Scheme (ETS) and CCUS project funding, as well as a full review of the highly-successful Global CemCCUS Conference, which took place in Oslo, Norway. Republished with kind permission.

All major cement sector projects are complex and face uncertainty. However, CO2 capture, utilisation and storage (CCUS) projects are complex in three dimensions. This comes from the nascent nature of the developing CCUS industry, which complicates an already difficult process.

Dimension 1 - Scope

CCUS projects are composed of multiple distinct sub-projects. These can be broadly grouped as capture, process and treatment, transportation and storage, utilisation, and sequestration. Within each of these there is technical complexity, including selection of capture technology; dehydration and purification of the captured CO2; the phase of the CO2 to be transported; the mode of transportation and any interim storage requirements; the decision to use or sequester the CO2.

The complexity is compounded by the interdependencies between each sub-project. The decision whether to utilise or sequester impacts the specification of the CO2 needed for transport, which impacts the design of the capture system and CO2 treatment. It also impacts material selection decisions throughout the value chain, and the distance to the user or sequestration site impacts the transport phase, which has impacts on designs throughout the chain. No decision can be made without impacting the other elements. To ascertain the optimal project architecture there must be an holistic understanding of each element and its relationships with each other.

Dimension 2 - Organisation

CCUS projects are rarely executed end-to-end by any one entity, as different parties undertake different sub-projects. Given the nascent nature of the CCUS value chain, the execution of each sub-project is not the core business of the contractor carrying it out. Cement companies excel at making cement but they have very little expertise in CCUS. Transportation of CO2, whether by pipeline, barge, rail or truck, is rarely the core business of the operator.

This organisational complexity is compounded by the need for all of the sub-projects to align with each other. No sub-project can take a final investment decision (FID) without certainty that the other sub-projects will also take FID in the required timeframe. The entire chain relies on the alignment of execution schedules of technically complex projects by entities that, while experienced in other fields, currently lack a core ‘CCUS expertise.’

Dimension 3 - Strategy

The third dimension of complexity relates to the strategic drivers for CCUS projects, which must serve a complex landscape of stakeholders. Internally there is a need to balance corporate commitments to net zero with commercial and productivity needs. The process must maintain economic efficiency while net zero goals are pursued. External stakeholders beyond wider society include government legislation and incentives.

There are also less obvious external stakeholder considerations, such as regional restrictions regarding the disposal of CO2. Germany, for example, prohibits onshore sequestration. This means that CO2 captured there must be transported to either the coast or a neighbouring country. This has implications on the internal stakeholder economic requirements: What is the most economically favourable solution: a pipeline, barge or railway?

Similarly, the export route has an impact on the technical choices. Are the risks of transporting dense phase CO2 appropriate for high population areas?

The interplay between internal and external stakeholders also manifests in the decision whether to sequester or utilise the CO2. In many geographies, there are differences between incentivisation for the utilisation and sequestration of CO2. In some instances, this presents an opportunity for the previous ‘waste’ stream to be monetised. Can the CO2 be sold or used to make a recycled carbon fuel (RCF)? This is a particularly pertinent question in the EU, as biogenic CO2 can be used to produce Renewable Fuels of Non-Biological Origin (RFNBO), with access to the associated incentive schemes. This dynamic may be the difference between a CCUS project being economically viable or not.

CCUS is the most important lever to decarbonisation in the Global Cement & Concrete Association’s roadmap to net zero CO2 emissions.

CO2 capture and utilisation will play a crucial role in cement sector decarbonisation.

Industry-specific challenges

The primary source of CO2 emissions in the cement process is the clinker-making process. Each capture technology has its own strengths and weaknesses:

Amines: An amine solution absorbs CO2 from the flue gas. This process is effective across a wide range of gas streams, from low CO2 up to 99% pure CO2. Amine systems are mature and reliable and have been used in various industries for decades. However, they are energy-intensive. Solvent degradation and emissions must also be carefully controlled.

Calcium carbonate looping (CCL): CCL utilises lime (calcium oxide) to capture CO2 from flue gases by forming calcium carbonate. A key advantage is the potential for lower energy consumption compared to amine-based processes. Additionally, it can be easily integrated with existing equipment, reducing implementation costs.

Adsorption: Temperature swing adsorption and vacuum pressure swing adsorption technologies capture CO2 by adsorbing it onto solid sorbents. They can be energy-efficient and offer flexibility, but may require high-pressure or high-temperature conditions. They also have lower capture efficiencies than liquid solvents.

Membranes: Membrane-based carbon capture separates CO2 from flue gases using selective permeable membranes. The process has low energy consumption and is easily scaleable, but membrane materials need to be optimised for high selectivity and permeability to be commercially viable.

Cryogenic separation: Cryogenic separation is a process in which the CO2-rich gas stream is separated from the residual gas over several stages. The technology can achieve high purity and is suitable at large scales. However, it typically requires significant energy input for refrigeration through a cryogenic processing unit (CPU). The energy requirements of a CPU are such that it is only efficient if the exhaust gas stream has a CO2 concentration >70-75%. The design of the CPU is based on ensuring the captured CO2 meets the purity requirements of the CO2 transport and storage sub-projects. The design of the CPU must be bespoke to the flue gas conditions and downstream purity requirements.

Sorbents: Sorbent-based processes use solid materials to adsorb CO2 from flue gases. For example, the double adsorber hot gas approach involves two sorbent beds that operate alternately to capture and release CO2. These processes offer potential for lower energy consumption and can be tailored for specific applications.

Cement kilns will require a variety of different CCUS technologies and project formats, depending on their individual circumstances.

Oxy-combustion: the solution for cement?

Given the interplay between the capture technology and the flue gas stream, it is important to consider whether changes to the clinker process itself can address CO2 capture challenges. One option is oxy-combustion, i.e.: burning fuel in pure oxygen. The combustion products are mainly CO2 and water vapour, with only trace amounts of other species - mainly NOx, SOx and particulate matter (PM). Capture of the CO2 from this highly pure stream is far easier than from conventional flue gas, mainly due to the lack of nitrogen. Laboratory tests performed by the European Cement Research Academy showed that oxy-combustion had no discernable effects on clinker quality. However, while already established in other industries, the application of oxy-combustion in cement production remains nascent.

First generation oxy-combustion: This method is best for kilns in excellent condition, ideally with tertiary air ducts and calciners. Necessary adaptations include heat-resistant seals and linings to minimise false air, which would otherwise reduce oxygen purity, as well as flue gas recirculation (FGR), which is used to moderate the higher temperatures caused by the use of pure oxygen.

FGR is especially important in the preheater to ensure proper dispersion and heat transfer of the dropped raw meal. By adjusting the exhaust gas volume returned to the process, the oxygen content can be maintained at the optimal level. In this process, the recirculated waste gas undergoes energetic cooling and drying before entering the clinker cooler to ensure both rapid cooling for clinker quality and to prevent water condensation. However, the specific heat capacity of CO2 requires higher thermal energy for FGR compared to conventional kilns. Thus, the benefits must be weighed up against an increased energy demand. Nevertheless, the resulting dry flue gas concentration can exceed 80% CO2.

Second generation oxy-combustion (no FGR): These units are designed to burn fuels in pure oxygen provided by a new air separation unit (ASU). There is no recirculation of the CO2-enriched flue gas and thus no need for energy-intensive cooling and drying. Oxygen is supplied via the cooler inlet and at the calciner and main burner.

With this type of kiln, the total amount of combustion gases drawn through the kiln, calciner and preheater are significantly reduced. To ensure the optimal ratio of clinker and CO2 in the preheater tower, the new clinker plant has cyclones with smaller diameters - and therefore smaller volumes - than conventional kilns of the same capacity. The calcination and sintering process at the main burner takes place at significantly different atmospheric and partial pressures than in conventional kilns.

To minimise the amount of false air, special kiln inlet and outlet seals with a temperature resistance of >1000°C are necessary. Separation of the gas flow in the cooler is also mandatory to ensure that the cooling air in the rear area is not drawn into the kiln, so that the purest possible oxygen atmosphere is maintained. To ensure this separation, pendulum plates or a lower shaft guide, where the clinker forms the gas barrier, are being considered. The heat generated at the cooler can be used directly to dry raw materials or fuels. The resulting flue gas concentration can be ≥93.5% CO2.

Air separation unit: All oxy-kilns require a source of oxygen, which can be obtained from an air separation unit (ASU). While ASUs are mature and proven, they represent yet another new technology for cement producers, which must select from different options: membranes, pressure-swing-adsorption (PSA), vacuum-PSA (VPSA) or cryogenic separation. PSA/VPSA are ideal for low volumes and low purity oxygen requirements, while cryogenic separation is preferred for high flow rates and applications that require highly-pure oxygen.

Pollution control: The main combustion pollutants from fossil fuels and alternative fuel mixes used in clinker kilns are: NOx, SOx, PM, organic compounds, polychlorinated dibenzo-p-dioxins and dibenzofurans, metals and their compounds, hydrogen fluoride (HF), hydrogen chloride (HCl) and carbon monoxide.

CO2 from oxy-combustion will benefit from the addition of a cleaning stage before being captured. Other industries usually use a two-stage gas cleaning approach. Dry gas cleaning removes NOx and PM, while wet gas cleaning removes sulphur-containing compounds, HCl and HF. Dependent on the use of the captured CO2, removal of NOx in particular is important to ensure that there are no significant metallurgy issues in storage, transportation

and sequestration.

Cryogenic processing unit (CPU): Having achieved a highly-pure stream of CO2, the oxy-kiln process lends itself well to cryogenic separation using a CPU, as it delivers a flue gas stream containing 85% CO2. In CPUs, a pressure swing absorber can be integrated to capture CO2 after cryogenic separation, enhancing purity levels by removing the remaining impurities. This cyclic process ensures efficient CO2 capture, while minimising energy consumption. It is possible to achieve CO2 purity of >99%. However, it remains an energy-intensive process and steps should be taken to improve efficiency, potentially via the use of waste heat recovery technology.

Finding solutions

Proper Front-End Loading will result in well executed projects with the correct scope.

Lessons learned from other industries show that investment in the early phases through front-end loading (FEL) is critical to establishing the strongest possible foundations for CCUS project success. Given the multi-dimensional complexities of CCUS projects for the cement industry, it is recommended that a systems approach to the project architecture is taken in the earliest phases. This is best done through the formation of an integrated team that not only possesses deep technical expertise in project management and systems engineering, but also demonstrates a nuanced understanding of the complex economics and stakeholder dynamics associated with CO2 capture utilisation and sequestration projects.

FEL is about investing time and effort to ensure that projects are viable before significant amounts of capital expenditure are committed. The process ensures that projects are correctly defined and planned, as decisions taken early on set the pathway to success or failure. It counts for little if you execute the wrong project, regardless of how well you execute it.

FEL is the key area of expertise of io consulting, a joint venture between Baker Hughes and

McDermott. It works with clients to create value in the front end and supports them by protecting value through the subsequent phases. io’s internal cost estimating database has been developed through successful execution of many CCUS projects across different industries.

Holistic project integration

It is vital to align the disparate elements of the CO2 value chain, from capture and purification to transportation and storage, and subsequent utilisation or sequestration. This integration is critical to ensure project feasibility and to allow each of the sub-projects to take its FID. This is best done with a systems approach to project execution, where the technical aspect of each sub-project is connected with the organisational and economic realities of the others, ensuring that all components work in harmony.

io consulting has pioneered a systems approach to energy transition projects, including CCUS projects that incorporate multi-industry emitters that capture and transport CO2 for onshore and offshore sequestration. Its Systems Optimiser tool enables it to integrate technical, cost and economic variables into a single environment and rapidly undertake multi-variable optimisation.

CCUS projects also need robust stakeholder management, where each party must understand the value drivers of the others. io often works in complex stakeholder landscapes like this, drawing on aspects of its Decision Quality framework.

Technical expertise

io consulting also has deep domain expertise in CO2, including phase properties, equations of state, static and dynamic simulation and flow assurance. The company has even designed a CPU that enables export specification CO2 compositions to be achieved without the need for an external refrigeration plant and associated infrastructure. This presents a significant advantage compared to other technologies.

io’s experts have also developed transportation projects that cover all CO2 fluid phases and transportation mechanisms, including onshore and offshore pipelines, in extreme environmental conditions and terrains. They are also experienced in rail and barge systems, including loading and unloading systems, transportation logistics, and marine shipping with loading and unloading systems.

With respect to storage, io consulting has access to subsurface expertise within the Gaffney Cline business. This includes geology, geophysics, petrophysics, reservoir engineering, drilling and completion and development planning / facilities engineering. The team of specialists has decades of experience in subsurface geology, process and injection of CO2.

Economic and regulatory expertise

CCUS projects often need external financial support. In addition to economic modelling, io’s energy economists have expertise in project financing. It has a 100% record in applying for government funding for energy transition projects. On the other side of the coin, io’s environmental and social experts have deep domain knowledge of the regulations and legislations surrounding all aspects of CCUS projects. It includes these assessments in the earliest phases of projects to ensure the risks and implications are included in the holistic assessment of project architecture and prevent unnecessary repetition of work.


io consulting aspires to work with its clients beyond FID. Acting as the owner’s engineer, io ensures continuity and consistency, reducing risks associated with transitioning between project phases and different contractors. It provides oversight and technical guidance during the execution phase, safeguarding the owner’s interests and ensuring that the project specifications and performance criteria are met. This approach enhances operational efficiency, while increasing project reliability, safety and compliance.


The correct definition of CCUS projects, so vital to their successful implementation, requires a thorough understanding of the interdependences between many dynamic elements. io consulting has already shown that it is possible to successfully deliver value on projects for some of the world’s leading cement companies, helping them conceptualise and design their decarbonisation solutions. This brings together expertise in major project development, including cost and schedule estimation; CO2 capture, processing, transportation, storage and utilisation; advanced simulation and flow assurance; safety and risk; environmental and social considerations; and project economics and financing. io consulting’s role in this critical journey is to bring its expertise to support the global cement and concrete industry to help make net zero happen

3 views0 comments


bottom of page