DOI: 10.3303/CET25117053 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 1 January 2025; Revised: 1 March 2025; Accepted: 24 May 2025 
Please cite this article as: Mawassi G., Di Pretoro A., Montastruc L., 2025, Accounting for Dynamics in Ranking CO2 Emissions Mitigation 
Strategies, Chemical Engineering Transactions, 117, 313-318  DOI:10.3303/CET25117053 
  

 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 117, 2025 

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of Chemical Engineering 
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ISBN 979-12-81206-17-5; ISSN 2283-9216 

Accounting for Dynamics in Ranking CO2 Emissions 

Mitigation Strategies 

Ghida Mawassi, Alessandro Di Pretoro*, Ludovic Montastruc 

Laboratoire de Génie Chimique, Université de Toulouse, CNRS/INP/UPS, Toulouse, France  

alessandro.dipretoro@ensiacet.fr  

The characteristic topic of the past decade research in the fields of chemical and energy industries can be 

identified in the continuous investigation of technological strategies aimed at the mitigation of CO2 emissions in 

order to meet the UE net-zero target by 2050. The solutions proposed so far cover a very wide range of 

applications and involve different aspects of the industrial sector, such as chemical-to-molecule, energy 

optimization, logistics etc. Therefore, in order to provide a more clear overview and to implement effective 

decision tools for the future selection of the most suitable technology according to the specific application, 

several classifications were conceived from a comparative perspective. The most established ones take into 

account the way CO2 is captured, the way CO2 is used or also the specific industrial domain where the carbon 

recovery is carried out. However, due to the very spread nature of the various methodologies, it appears very 

difficult to find any classification able to include all of them. Furthermore, when comparing the effectiveness of 

different technologies, it should be accounted for the fact that not all of them have currently achieved the same 

level of development and deployment. The purpose of this research work is then to find one or more common 

aspects among the different CO2 emissions mitigation strategies and to classify the available options based on 

that. Since the carbon dioxide accumulation in the atmosphere results from the gap between positive and 

negative CO2 contributions over time, a new possible classification based on dynamic response function was 

explored. In order to uniquely characterize the dynamic impact of the selected approach, the removal magnitude 

and the CO2 release delay were identified as the two parameters to be used as criteria for the various categories. 

Therefore, their respective values for each available technology were quantified and then employed to reclassify 

all of them accordingly. This new classification showed that the most effective way to mitigate carbon emissions 

is to convert CO2 into long lasting products while powering the process with renewable energy. Therefore, 

transforming the process to a negative emission process. For a future perspective, the new categories thus 

obtained could be considered as a starting point to build decision tools to effectively assess the impact over 

time of CO2 removal approaches and make more reliable predictions in terms of long-term emissions. 

1. Introduction 

Due to the growing concerns about climate change in recent years and the pressing need to meet UE net zero 

target, the mitigation of anthropogenic carbon dioxide emissions has gained global attention. Many 

environmental innovations, from CO2 capture to CO2 conversion into useful products and from energy 

consumption optimisation to relying on renewable energies are the key towards greener processes. Regarding 

this wide diversity, a classification of these methods is needed to guide chemical engineers, through influence 

of each one when designing a sustainable process. This classification should cover all these approaches with 

divergent paths. Many reviews and classifications are found in literature regarding CO2 management 

techniques, reflecting the diverse approaches and applications for capturing, using, and mitigating CO2 

emissions; however, none can be used as a powerful tool that gives an overview on all strategies and helps to 

select the most appropriate one in a certain application or process. Numerous flaws and restrictions such as the 

intersection between categories or the missing of certain features, lead to a misleading or incomplete view of 

overall CO2 emission reduction strategies. In addition, the CO2 cycle and its dynamic behaviour is not explored 

in any of the classifications mentioned, failing to reflect the real impact of each method. 

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mailto:alessandro.dipretoro@ensiacet.fr


Various reviews categorized these strategies according to different criteria such as the method used to reduce 

a carbon emission like different carbon capture or utilization techniques, or depending on the current 

development stage or maturity of each method. Other interesting classifications divide them according to their 

adaptability for each industrial sector, or the phase of their implementation in the process. All these divisions 

are illustrated in Figure 1 and further detailed below. 

Starting with the carbon capture and storage (CCS), a method that relies on capturing CO2 emissions at the 

source and storing them underground or in other secure locations such as deep ocean reservoirs to prevent 

them from entering the atmosphere, it was divided in numerous subcategories. First, with respect to the nature 

of the processing technique whether it is industrial or natural (Quang et al., 2023), or regarding the source of 

the CO2 captured, air for direct air capture or flue gas for indirect capture indirect (Pires et al., 2019) and finally 

based on the capturing technique (precombustion, post-process, oxycombustion methods, direct air capture 

(DAC) and chemical looping combustion (CLC)) (Kheirinik et al., 2021), (Wilberforce et al., 2021). 

Strategies are also classified depending on CO2 utilization strategies in accordance to the nature of utilization 

(direct or conversion into valuable product) or the type of product obtained (fuel, biofuel, chemicals and 

application in thermodynamic processes) (Osman Ahmad et al., 2020).  

Another common classification in literature is to split the CO2 mitigation strategies based on the sector where it 

is applied. CO2 management is also specific for every industry such as iron and steel, cement, chemical and 

petrochemical industries, and petroleum refineries, where each have specific approaches tailored to their unique 

emission profiles (Kuramochi et al., 2012). Even though this classification provides a framework for 

understanding the wide range of strategies available for managing CO2 emissions across various sectors and 

applications, however it is not englobing all possible applications for instance transportation. 

Concerning the classification exploring side management where different strategies are implemented, it includes 
supply-side, demand-side, and end-of-pipe solutions (Manan et al., 2017). Supply-side strategies focus on 
reducing emissions at the source by modifying inputs or production processes, such as using low-carbon fuels, 
increasing energy efficiency, or incorporating renewable energy. These approaches aim to lower the carbon 
intensity of industrial activities from the start. Demand-side strategies concentrate on reducing CO2 emissions 
by changing consumption patterns. This involves improving product efficiency, minimizing waste, and promoting 
low-carbon products. The goal is to decrease the demand for carbon-intensive goods and services. End-of-pipe 
solutions address emissions after they have been produced, typically through carbon capture and storage (CCS) 
technologies. These methods capture CO2 from flue gases for either permanent storage or repurposing. 
Finally, classifications can be established on the current status of CCS development and the type of mitigation 
strategy employed. This approach divides strategies into those that are commercially viable and in widespread 
use, those that are still in the demonstration phase, and those that remain in the research and development 
stage (Bui et al., 2018). However, these classifications, while useful in organizing different approaches, do not 
serve as direct tools for estimating the efficiency of CO2 mitigation within the process industry. The efficiency of 
mitigation efforts depends on specific factors such as the technology used, the scale of implementation, and the 
unique conditions of each industrial process. Therefore, they provide a conceptual framework for understanding 
the landscape of CO2 management strategies, but they must be complemented by detailed, process-specific 
analyses to accurately assess mitigation efficiency in the process industry. 

      

Figure 1 Criteria of CO2 reduction’s categorization in some reviews 

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The new classification system presented in this work serves as a practical tool for selecting the most appropriate 
CO2 mitigation strategy based on specific applications. This system evaluates all methods by considering their 
long-term effects on atmospheric CO2, incorporating key factors such as the time delay of CO2 re-emission 
(when applicable) and the magnitude of CO2 removal relative to the function performed. By accounting for 
variations in re-emission delays, which can range from short-term to long-term periods, and assessing the 
effectiveness of each strategy based on its CO2 removal capacity, this classification offers a more precise 
method for evaluating the impact of different approaches. This allows the selection of strategies that are 
optimized for both immediate CO2 reduction and long-term climate impact, tailored to the specific role CO2 plays 
in the process, whether it is stored, utilized, or transformed into valuable products. 

2. Overview and analysis of carbon dioxide removal technologies 

Measures to mitigate the emissions of CO2 can vary substantially in terms of strategies and techniques, each 

with its own limitations. Some approaches, such as CCS, do not eliminate CO2 but instead prevent it from 

entering the atmosphere by capturing and storing it underground. CCS is a containment strategy, not a solution 

to the root cause of emissions. 

Others focus on reducing emissions at the source, like improving energy efficiency, or using low-carbon 

materials in construction or changing raw material. For instance, research indicates that replacing traditional 

limestone-clay mixtures with civil construction waste in cement production can lower CO2 emissions by 8.1% 

(Costa et al.,  2020), and in Bahrain, implementing better insulation and glazing in air-conditioned commercial 

buildings led to a 25% reduction in energy consumption and a 7.18% decrease in net CO2 emissions (Radhi et 

al., 2009).However, more advanced approaches go beyond just capturing or reducing CO2—they repurpose it 

for practical applications. Such as in the food and beverage industry where CO2 is used to carbonate beverages, 

while in other industries, it serves as a utility for chilling. Additionally, CO2 can be used to enhance oil and gas 

recovery, helping to maximize resource extraction while simultaneously sequestering carbon. In this case, as 

soon as it is used, carbon dioxide will be reemitted in the atmosphere. But more important technologies convert 

CO2 into valuable products such as synthetic fuels, building materials, or chemicals, reducing the need for virgin 

resources. By integrating CO2 into useful applications rather than simply storing it, these solutions create a more 

sustainable and circular approach to carbon mitigation. Here, it is important to distinguish between two types of 

carbon conversion; conversion to short and long-life products. The reemission of CO2 occurs quickly with short-

lived products like the production of urea, used as fertiliser from CO2, or the synthesis of synthesise compounds 

such as salicylic acid, a crucial component of aspirin. However, by converting CO2 to long life products carbon 

dioxide is sequestered for extended periods. By converting CO2 into plastics and polymers, durable products 

that can be used in various industries are obtained. These materials, traditionally derived from fossil fuels, can 

now be produced from CO2, helping to sequester carbon and reduce dependency on fossil resources. 

Similarly, construction materials can be obtained from CO2 through carbon mineralization. By reacting CO2 with 

minerals, stable carbonates are created that can be utilized to make carbon-absorbing concrete and other 

construction materials. These materials recycle CO2 into useful products, effectively locking away carbon for 

extended periods of time and supporting a circular economy. In both cases, the conversion of CO2 into long-

lasting products not only helps sequester carbon but also supports sustainable material use and reduces the 

environmental impact of production. Different approaches have been developed to lower atmospheric carbon 

dioxide levels, as this section has described. To make a process greener, process engineers must consider all 

available options and decide on the optimal one. The particular process type, the circumstances, and the 

available resources should all be taken into consideration while making the choice. This guarantees that the 

selected course of action not only efficiently lowers carbon emissions but also remains viable and sustainable 

within the specified parameters. 

3. New classification and possible applications 

3.1 Presentation of the new classification 

The effectiveness of various strategies in reducing CO2 emissions is not equivalent; thus, the primary aim of the 

new classification is to underscore the efficacy of CO2 removal associated with each method. Evaluation will 

take into account two main trait of the strategy: the timeframe and the functional role. 

To begin, the assessment of this effectiveness should not be limited to the immediate and direct removal of CO2 

but should also consider the long-term implications to provide more accurate predictions regarding emissions. 

In this regard, it is essential to differentiate between scenarios where CO2 emissions are merely reduced, those 

where CO2 is removed and subsequently re-emitted within short (days, months) or large (years, centuries) 

intervals, and measures that can prevent emissions in specific applications. 

In addition to the time delay, the functional role that CO2 plays in each method can also be used to predict the 

impact of CO2 mitigation methods. This role transitions from methods that primarily involve CO2 sequestration 

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to those that utilize CO2 as a raw material, utility, and ultimately, a final product. The quantitative impact of this 

evolution can be calculated by evaluating the CO2 emissions per unit of product across different applications, 

or comparing scenarios with and without the proposed strategy. The efficacy of a method can be obtained by 

evaluating the extent to which it diminishes CO2 emissions in comparison to the same process conducted 

without the application of that strategy. Thus, a more significant decrease in emissions attributable to the 

strategy indicates a higher level of success in alleviating environmental consequences. 

Through the assessment of the magnitude of CO2 removal and the timing of its release for each technology, 

CO2 mitigation strategies have been restructured into new categories that better represent the influence of these 

technologies on atmospheric CO2 levels. Looking ahead, these redefined categories could lay the groundwork 

for the development of decision-making tools that effectively analyze the long-term consequences of CO2 

removal strategies. Such tools would improve the precision of predictions concerning future emissions, enabling 

more strategic decision-making in climate change mitigation efforts. 

3.2 Different aspects throughout the process 

Usually process operations are divided into several essential steps, each playing a vital role in the environmental 

impact and carbon emissions of the overall process. The first step in all productions is the selection of raw 

materials, then their transportation to the site. The latter contribute significantly to car bon emissions, depending 

on the distance and transportation mode. After their arrival at the location, the raw materials must be prepared 

and treated. This can involve cleaning, refining, or other pre-production procedures to guarantee the resources 

fulfill the criteria needed for production. 

The second stage or the core of the process is the production phase itself, where the actual transformation of 

raw materials into the final product occurs. This step typically requires various forms of energy and utilities. The 

efficiency and environmental impact of this stage depend heavily on the energy sources used and the technology 

employed. Finally, in the last level the process results in the production of the final product, ready for distribution. 

Throughout all these steps, it is essential to consider the environmental implications, such as raw material and 

final product selection, energy consumption, emissions, and waste generation, to ensure the process is as 

sustainable and eco-friendly as possible. The selection and treatment of raw material highly impacts the carbon 

emissions as explained in the previous section. Even though treating raw material can reduce emissions during 

the production process, this approach alone doesn’t play a role in removing CO2 from the atmosphere, it only 

minimizes the carbon footprint of the operation.  

The long-term effectiveness of this approach depends on the type of products being created. Products with 

longer lifespans, such as polymers or building materials, can store the captured CO2 for decade or even 

centuries, delaying its re-release into the atmosphere. In contrast, products with shorter lifespans, such as 

certain chemicals, fertilizers or fuels, will eventually release the stored carbon back into the atmosphere within 

days or months. Thus, the selection of CO2 as a raw material, combined with the production of long-life products, 

represents a powerful tool in achieving meaningful carbon reduction and enhancing sustainability efforts. 

Now, considering the overall utility aspect that can include the transportation, the use of CO2 for other utility 

goals. For example, adapting CO2 as a chilling agent, for cryogenic cooling systems or refrigeration, is a sensible 

and environmentally responsible strategy. Because this application uses CO2 that has already been captured 

or made available, fewer alternative refrigerants that might have a higher global warming potential or produce 

and use more CO2 emissions are needed. This usage of CO2 does not, however, actively remove it from the 

atmosphere, but it may lessen the environmental impact of alternative refrigerants by reusing already-existing 

CO2. By using CO2-based systems, we can reduce additional climate change emissions while making use of a 

widely available material, improving the sustainability of cooling solutions. 

Also, during transportation operations—whether it involves raw materials supply to the site or finished products 

distribution—it is essential to explore alternatives to conventional fossil fuels. One effective approach is to use 

fuels derived from CO2 and biofuels. Although these fuels may re-emit carbon dioxide into the atmosphere 

relatively quickly, often within days, they offer distinct environmental advantages over traditional fossil fuels. 

Fuels derived from CO2 have already contributed in capturing carbon from the atmosphere when being 

produced, thus offsetting some of the emissions generated at their combustion. This means that, while they do 

re-release CO2, the overall impact on atmospheric carbon levels is reduced. Moreover, these fuels tend to emit 

less carbon compared to conventional fuels, further lowering their environmental footprint. 

Similarly, biofuels, produced from renewable organic materials, can also serve as a more sustainable alternative 

to fossil fuels. While biofuels do release carbon when burned, the plants used to produce them absorb CO2 from 

the atmosphere during their growth, creating a more balanced carbon cycle. Incorporating these alternative fuels 

into the transportation process not only supports the reduction of greenhouse gas emissions but also aligns with 

broader goals of sustainability and carbon management. By transitioning away from conventional fossil fuels 

and embracing these greener alternatives, the overall environmental impact of transporting raw materials and 

distributing products can be significantly mitigated. By analogy, using green fuels for power generation during 

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the production process has a comparable impact to their use in transportation. the impact of utilizing green fuels 

for transportation is similar to that of using them for power generation during the production process. 

Lastly, renewable energy sources, such as solar, wind, hydroelectric, and geothermal power, offer an even more 

optimal solution for power generation. Unlike green fuels, which may still result in CO2 emissions during use, 

renewable energies do not produce any direct emissions during operation. This makes renewable energy an 

ideal choice for creating greener and more sustainable production systems. 

3.3 Applying the new classification to the process design 

To refine the classification in a clearer way, it is structured around two axes: the time axis referring to the delay 

for CO2 re-emission in the atmosphere after the implementation of a CO2 mitigation strategy and it can be divided 

into days, moths, years and centuries and on the other hand the functional axis that states the place of the 

strategy in the process if applied on raw material, products or utility).  

Thus, the effectiveness of each CO2 mitigation technique should be assessed in terms of how long it takes for 

captured CO2 to be released back into the atmosphere. This entails choosing raw materials, energy sources, 

and industrial techniques that maximize the amount of time before any CO2 is produced in addition to minimizing 

emissions. A thorough evaluation at every stage of the process is necessary. Emphasizing choices that support 

efficient CO2 capture and long-term carbon storage when choosing raw materials. Production energy sources 

should be selected according to how effectively they may reduce CO2 emissions, such as renewable energy 

sources like solar and wind or green fuels Technologies that both shorten the time until any CO2 is captured 

and lower it immediately should be implemented throughout the production phase. 

In the transportation and distribution stages, alternative fuels and logistics strategies should be evaluated for 

their ability to reduce carbon emissions and incorporate re-emission delay. The choice of biofuels or fuels 

derived from CO2 can be made on the basis of how well they sequester carbon dioxide and reduce emissions 

when compared to conventional fossil fuels. 

Lastly, in order to extend the period of carbon storage, the end-of-life phase of products needs to be taken into 

account. Long-term sustainability and climate goals can be attained by designing products with longer carbon 

sequestration in mind and making plans for recycling or disposal techniques that further postpone CO2 re-

emission. By using this method, process designs are guaranteed to be efficient in lowering direct carbon 

emissions and promoting more general environmental goals. 

For example, properly treating raw materials or replacing them with alternatives can reduce carbon emissions 

in the cement industry by approximately 4% and up to 8% recpetively (Costa et al., 2020). Typically, the raw 

material processing stage is considered to contribute to a maximum CO₂ reduction of 10%. In this case, the 

process stage is assessed along the process axis, while the time axis remains at zero, as it only reduces 

emissions rather than removing CO₂ entirely.On the other hand, converting CO₂ into propylene for example can 

achieve a reduction of 80–87% per ton of product (Tähkämö et al., 2022) in CO₂ emissions per ton of product, 

with re-emission occurring over several decades. More examples can be found in Figure 2 below. 

 

 

Figure 2 CO₂ mitigation strategies categorized by process stage and re-emission time delay. 

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As shown in Figure 2, methods applied on raw material generally has a low CO2 mitigation potential, meaning 

its impact on reducing emissions is relatively limited. In contrast, utility can achieve a mitigation potential of up 

to 50%, making it a more effective option. Among all categories, focusing on strategies that target  final products 

demonstrate the highest mitigation potential, significantly reducing emissions. However, the re-emission of CO₂ 

varies depending on the specific process and application, leading to different delays in its eventual release. 

4. Conclusions 

The study done in this paper has successfully addressed the research objectives, as shown by the results that 

were obtained. It highlighted the importance of the dynamic elements, especially when computing the CO2 

mitigated, by a thorough and precise examination. Furthermore, the findings underscored that different CO2 

mitigation strategies have varying levels of impact over short-term and long-term periods, highlighting the 

necessity of tailoring approaches to achieve optimal results. These outcomes will be crucial instruments for 

directing the choice of a suitable approach suited to the particular goals in the process industry. Decision-makers 

can guarantee that activities are both efficient and effective regarding carbon foot print by comparing the 

selected method with the intended goals. 

Acknowledgments 

This work benefited from State aid managed by the Agence Nationale de la Recherche under the 

Investissements d'Avenir programme, reference ANR-18-EURE-0021. 

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	Accounting for Dynamics in Ranking CO2 Emissions Mitigation Strategies