Bridging the Lab-to-Plant Gap: Why CESAR-1's Journey from Promise to Practice Takes More Than a Decade

The technology that surrounds people’s lives is not developed in a vacuum, without concern. If we consider the technology itself, there are already examples that literally come out of an SF movie, such as vehicles flying through the sky and the ability to control objects simply by using the mind. However, can we easily see those technologies commonly in daily life? If not, why?

To resolve this sort of question, it is much more understandable to accept a gap between a literal technology and commercialised technology when it comes to introducing the concept of technology readiness level (TRL)

According to Lezama-Nicolás et al. (2018), TRL is defined as an indicator of technology maturity, quantified on a scale from TRL 1 to TRL 9, to increase certification in real systems.

The significance of TRL is to meticulously identify unexplored problems, such as those not significantly considered at lab-scale but increasingly considered at plant-scale, thereby easily convincing decision-makers of the technologies’ reliability.

For instance, in recent decades, numerous research studies have been published in various journals to address carbon dioxide emissions from factories.

However, among all the novel research, in real industrial settings, methods for controlling carbon dioxide emissions still widely use MEA, an amine-based solvent, despite its critical disadvantages, including its high corrosivity and the need for high regeneration energy.

Nevertheless, since this technology was patented by Bottoms in 1930, there are fewer concerns about MEA producing unpredictable results, which is why it is still widely used today. However, CESAR-1, a new amine-based solvent, has recently attracted attention for its potential to address MEA’s disadvantages and has demonstrated reliability sufficient for use at the plant scale.

This paper will examine why amines, particularly the CESAR-1 solvent, have gained attention as a technology to mitigate global warming, not only from an academic perspective but also by tracing their timeline and trajectory in genuine industrial practice.

CESAR-1 - academic perspective

CESAR-1’s academic perspective is well-described in my research paper (ongoing publication), and its defining characteristics can be summarised briefly as its binary composition(AMP/PZ), which compensates for each other’s weak characters. By incorporating each amine-based solvent’s advantage, CESAR-1 has a higher CO₂ loading capacity with lower regeneration energy, attributed to its combinational characteristics.

1.  CESAR-1 has a higher CO₂ loading capacity compared to the predominant solvent, MEA. This superiority is attributed to the amine groups of PZ (Piperazine). When the solvent captures a CO₂ molecule in the absorber, PZ’s nucleophile conducts a nucleophilic attack on the electrophilic carbon of CO₂, forming a carbamate. This procedure is rapid, which substantially

increases CO₂ loading. In addition, another nucleophilic site on PZ leads to the formation of a dicarbamate.

2.  CESAR-1 has a lower regeneration energy, which is derived from AMP’s character.

Similar to PZ, AMP (2-amino-2-methyl-1-propanol) has a tertiary amine structure. The critical difference is, however, that AMP’s amine group is surrounded by two methyl groups, causing a hindrance effect that hardly makes a carbamate; instead, AMP requires an additional way to reserve a CO₂ as a form of bicarbonate. The bicarbonate contributes significantly to mitigating regeneration energy - the amount of heat to return from CO₂-reach solvent to CO₂-lean solvent - in the stripper.

3.  Li et al. (2023) attribute the reduction of regeneration energy to the introduction of alternative regeneration pathways. Specifically, in addition to the reverse reaction of the absorption process, the presence of protonated-AMP and protonated-PZ provides alternative pathways.

2. CESAR-1 - timeline (Early / Present)

EU’s CESAR(2008-2012)

CESAR-1 was originally developed from the EU’s CESAR(CO₂ Enhanced Separation and Recovery) project from 2008 through 2012. This project set a goal to substitute MEA with an alternative solvent, as MEA has critical shortcomings, as follows:

MEA requires excessive regeneration energy (approximately 3.8-4.2 GJ/tons CO₂)

MEA requires a high solvent makeup cost due to solvent losses from oxidation and thermal degradation.

Once NO₂ and SO₂ are present in the process, the likelihood of degradation increases.

The optimal ratio of AMP (3 M, 27 wt%) and PZ (1.5 M, 13 wt%) was established in the project and consistently used in subsequent research, working as a benchmark.

The ESBjerg pilot test, conducted in 2011 at the end of the EU CESAR project, demonstrated the CESAR-1 system’s process operators, such as L/G, Stripper pressure, etc. Each process operator contributes to energy efficiency.

1.  L/G ratio (Liquid-to-Gas): The Liquid-to-Gas ratio in an absorber (L/G ratio) can also be a relevant operating parameter for the CO₂ capture efficiency of an absorption process. If the L/G ratio is too low, there may be insufficient solvent to absorb all or most of the CO₂ in the gas, and a large proportion of the CO₂ may be unabsorbed. An excessively high L/G ratio, on the other hand, would result in an unnecessary amount of solvent being heated to the operating condition, thereby increasing the reboiler duty and leading to higher energy costs. In addition, an optimal L/G ratio tends to minimise the load on other process equipment. Thus, the L/G ratio has become an important operating variable to achieve target CO₂ capture efficiency with minimal solvent flow.

2.  Lean loading /Rich loading/Working capacity or difference of two: The working capacity of the solvent is the difference between the lean loading and the rich loading of the solvent stream. The larger the working capacity, the less solvent is needed to remove the CO₂ from the flue gas, therefore requiring a smaller L/G ratio and less reboiler duty. However, too low a lean loading results in higher heat requirements for solvent regeneration, increasing energy

expenditure. If the rich loading is too high, a pinch point-the state of an absence of driving force to absorb the CO₂-may occur near the tail of the absorber tower, where the solvent has loaded with as much CO₂ as it can absorb.

After the EU CESAR project (2019-present)

After the EU CESAR project ended, some research is being conducted to secure reliability through long-term operation in the real plant.

-          ALIGN-CCUS CESAR-1 campaign (2019-2020) at TCM, Mongstad, Norway

Key finding: AMP/PZ emission and solvent stability were evaluated with CO₂ capture efficiencies of 90-98% and a specific reboiler duty(SRD) of 3.1-3.9 GJ/tons CO₂. The study focused mainly on venting solvents (AMP and PZ) to the atmosphere rather than on the CO₂ capture step. The degradation products (such as formamide and morpholine) and solvent concentrations were measured to evaluate the stability of the compounds.

-          CESAR-1 testing with Combined Heat and Power (CHP) Flue Gas at TCM at TCM, Mongstad, Norway (2020)

Key finding: Under high-CO₂ capture operation, capture efficiencies of 97-99% were achieved, with specific reboiler duties (SRD) of 3.41-3.54 GJ/tonne CO₂ captured. Even at ultra-high capture efficiencies, the regeneration energy was found to be 10-15% lower than the MEA benchmark of 3.6 to 4.0 GJ/tonne CO₂, demonstrating CESAR-1’s superiority to MEA.

-          ALIGN-CCUS Niederaussem Pilot Plant CESAR-1 Long-term Test Campaign at RWE Power Station Niederaussem, Germany (near Bergheim) (2019-2022)

Key finding: Through long-term operation (about 40 months, 28,800 hours), the projects quantified CESAR-1’s linear degradation (0.044-0.202 kg amine/t CO₂). Several strategies to manage the degradation - ion exchange, activated carbon, and NO₂ removal - were suggested, where some of the strategies facilitated the degradation.

-          2022 Greenhouse Gas Control Technologies Conference by NETL

Key finding: Based on data from TCM ALIGN-CCUS, the real plant data had an accuracy ±5% lower than the process model, demonstrating CESAR-1’s reliability for establishing common industrial plants.

3. CESAR-1: Remaining Gaps Toward Commercialisation

In pilot demonstrations at TCM, AURORA, cement plants, and metal recycling facilities, CESAR-1 has been shown to outperform the second-generation solvent MEA in regard to energy efficiency and stability. Despite these accomplishments, several critical issues still need to be resolved before commercial deployment.

A first issue is degradation and lifetime prediction. Pilot and long-term testing have shown that degradation is highly dependent on flue gas composition, particularly high NOₓ and dust concentrations in cement and metal-processing plants. The existing models do not predict solvent lifetimes outside pilot environments, and unresolved nitrogen balance issues indicate an incomplete understanding of degradation pathways.

Emissions are a second challenge. AMP/PZ emissions are lower or similar to those of MEA. However, amine, nitrosamine, and aerosol emissions can vary greatly between plants with

different pretreatment systems. Furthermore, there are no universal guidelines for long-term regulatory compliance below stringent emission thresholds, which is another major obstacle.

Lastly, while pilot studies suggest that regeneration energy is 10-20% lower than MEA, the economics depend on heat integration and compression, as well as other process optimisations, and those reductions in energy costs remain insufficient to significantly decrease overall operating costs. So far, no solvent system, including CESAR-1, has demonstrated a clear breakthrough in overall system cost reduction.

Conclusion

CESAR-1 can be regarded as a technically mature solvent that has been under development for more than fifteen years with the explicit aim of replacing MEA. Furthermore, it has been continuously matured from laboratory-scale development to pilot-scale demonstration and, finally, to testing under representative industrial operating conditions. In this sense, there is a widespread agreement that the technical development of CESAR-1 has been completed.

At the same time, the long timeline raises questions about why it has taken more than a decade after the MEA replacement demand was proposed. The industrial context that initially justified CESAR-1’s deployment may have changed. Industrial structures, regulatory environments, and decarbonisation strategies have evolved, changing the relevance of specific capture technologies, such as amines, relative to other options. From this perspective, the protracted process of commercialisation does not seem to be simply a technical issue, but a reflection of structural and institutional impediments that slow the transition of technology into commercial operation.