Current Developments of Carbon Capture Storage and/or Utilization–Looking for Net-Zero Emissions Defined in the Paris Agreement

An essential line of worldwide research towards a sustainable energy future is the materials and processes for carbon dioxide capture and storage. Energy from fossil fuels combustion always generates carbon dioxide, leading to a considerable environmental concern with the values of CO2 produced in the world. The increase in emissions leads to a significant challenge in reducing the quantity of this gas in the atmosphere. Many research areas are involved solving this problem, such as process engineering, materials science, chemistry, waste management, and politics and public engagement. To decrease this problem, green and efficient solutions have been extensively studied, such as Carbon Capture Utilization and Storage (CCUS) processes. In 2015, the Paris Agreement was established, wherein the global temperature increase limit of 1.5 °C above pre-industrial levels was defined as maximum. To achieve this goal, a global balance between anthropogenic emissions and capture of greenhouse gases in the second half of the 21st century is imperative, i.e., net-zero emissions. Several projects and strategies have been implemented in the existing systems and facilities for greenhouse gas reduction, and new processes have been studied. This review starts with the current data of CO2 emissions to understand the need for drastic reduction. After that, the study reviews the recent progress of CCUS facilities and the implementation of climate-positive solutions, such as Bioenergy with Carbon Capture and Storage and Direct Air Capture. Future changes in industrial processes are also discussed.


Introduction
Due to the Industrial Revolution, fossil fuels (coal, oil and gas) were unlocked as a new energy resource. Their excessive use has led to several negative impacts such as global climate change [1]. Figure 1 presents the surface air temperature anomalies between 1979 and 2020. For example, comparing with September 2016, September 2019 was the warmest month in the data record, which was 0.57 • C warmer than the average temperature from 1979-2010 [1].
Natural causes are also responsible for this effect. However, greenhouse gases from human activities including population growth, deforestation, agriculture, urbanization (urban heat islands), and the resulting changes in consumption patterns are responsible for more than 95% of global warming [2]. The greenhouse contribution in the temperature variation is evident, responsible for about 1 • C, more than other anthropogenic sources and natural variations.
The principal greenhouse gas related to global climate change is carbon dioxide (CO 2 ). Other gases, in minor quantities, are also responsible, such as methane (CH 4 ), water vapor (H 2 O), nitrous oxide (N 2 O) and fluorinated gases (F-gases), specially hydrofluorocar- In order to combat climate change and achieve decarbonization, several methods have been studied and implemented: a massive development of clean energies (renewable energy sources); fossil fuel consumption reduction by switching to lower-carbon alternatives, e.g., coal to gas; energy efficiency increase in industrial applications and the power sector, particularly in technologies used to convert fossil fuels into energy; carbon capture and utilization/storage techniques [2,[5][6][7]. The employment of all of the options mentioned above will be required because CO 2 emission abatement became a global priority. However, at the current state of development, the levels of risks and the costs, non-fossil fuel energy alternatives cannot meet our need for energy fed by fossil fuels. Additionally, any quick change to non-fossil energy sources, even if this action was possible, would result in large disruptions to the existing energy supply infrastructure with substantial consequences to the global economy [8].
In the Paris Agreement, 196 parties decided to establish a long-term goal to keep the worldwide average temperature increase below 2 • C above pre-industrial levels and limit the increase to 1.5 • C, since this would significantly reduce the risks and effects of climate change [9][10][11]. Consequently, to obtain a sustainable low carbon future, global CO 2 levels should be drastically reduced by promoting the actions and investments needed. This limitation in the worldwide temperature implies immediate and decisive actions on climate change to avoid some of the worst climate impacts and reduce the chances of extreme weather occurrences around the world.
Thus, to meet mid to long-term CO 2 emissions targets, cost-effective CO 2 capture from fossil fuel use and subsequent sequestration options need to be evaluated, as well as the utilization of (captured) carbon dioxide as a feedstock for new products. Figure 2 shows the CO 2 life-cycle considering two pathways: carbon capture and storage (CCS) and carbon capture and utilization (CCU). Analysis of life-cycle of CO 2 with capture and storage, and capture and utilization from main sources pathways (based on Sekera and Lichtenberger [12] and Bui et al. [13]).
Broadly recognized as having an enormous potential to meet climate change targets, CCS and CCUS appear as solutions to deliver low carbon heat and power, decarbonize the industry, and, more recently, facilitate the net removal of CO 2 from the atmosphere [14].
This article aims to review the overall CCS and CCUS strategies implemented to fulfil the climate change ambition established in the Paris Agreement of 2015. The approach to obtain a climate-neutral-an economy with net-zero greenhouse gas emissions-implies large changes in all the economic sectors, as well as energy, transport, industry, and agriculture.
First, the values of actual CO 2 emissions are presented, and it is analyzed the impact of COVID-19 in the first quarter of 2020. After that, Carbon Capture and Storage and Carbon Capture, Utilization, and Storage strategies to combat CO 2 emissions are described. CO 2 capture technologies, classified into three groups, precombustion, oxy-fuel and postcombustion systems, are presented as well as the leading technologies used for CO 2 capture. CCUS's current development, focusing on the facilities and projects working in Europe, is presented.
Two commonly used technologies of climate-positive solutions are briefly described, which are bioenergy with carbon capture and storage (BECCS) and direct air capture (DAC). In conclusion, the future of industrial processes, that use fossil fuels as raw materials and release CO 2 emissions, is analyzed.

CO 2 Emissions
In 2019, global energy-related CO 2 emissions reached 33 gigatonnes (Gt), approximately [15]. This resulted mainly from a sharp decline in CO 2 emissions from the power sector in advanced economies (Australia, Canada, Chile, European Union, Iceland, Israel, Japan, Korea, Mexico, Norway, New Zealand, Switzerland, Turkey, and United States.), because of the expanding role of renewable sources (mainly wind and solar photovoltaic systems), fuel switching from coal to natural gas, and higher nuclear power output. However, the total emissions, in the rest of the world, increased. Figure 3 shows the gigatonnes of CO 2 emitted by developed countries, the rest of the world, and total emissions from 1990 until 2019 [16]. Figure 4 shows the global greenhouse gas emissions (%) by sector in 2020 [16]. The economic sector which had the highest share of carbon dioxide emissions from fossil fuels and cement was the power sector. With a 44% of emissions, this was more than the combined share of both industry and surface transport. These three sectors of the economy make up the majority of the world's CO 2 emissions.
Covid-19 had an enormous impact on energy demand and, therefore, on CO 2 emissions. The drastic curtailment of global economic activity and mobility during the first quarter of 2020 pushed down global energy demand by about 3.8% compared with the first quarter of 2019 [15]. CO 2 emissions were about 5% lower in Q1 2020 than in Q1 2019, almost twice as large as all previous declines since the end of World War II. By sectors, emissions from coal, oil, and natural gas declined about 8, 4.5, and 2.3%, respectively. By regions, a considerable decrease of CO 2 emissions was observed: −8% in China, −8% in the European Union (EU), and −9% in the United States [15]. However, this decline was punctual; it will not be enough to resolve climate change problems.  In April 2020, McKinsey Global Institute published an overview of several scenarios of projected global CO 2 emissions that helps to understand the future. Climate Action Tracker [18] also provide these data. The scenarios are shown in Figure 5, where global CO 2 emissions in each scenario are projected. All pathways include energy-related emission, industry-process emissions (e.g., from cement production), emissions from deforestation and waste, and negative emissions (e.g., from reforestation and carbon-removal technologies such as bioenergy with carbon capture and storage, and direct air carbon capture and storage). Emissions from biotic feedbacks (e.g., from permafrost thawing, wildfires) were not considered. The red lines represent warming projections if policies are not applied: the lower bound is a "continued growth" pathway based on the IEA's World Energy Outlook 2019 current policies scenario; the higher bound is based on IPCC's Representative Concentration Pathway 8.5 [19]. It is possible to observe the need for immediate reduction of GHG emissions.  According to this study, if no changes are applied, the continued growth will lead to about 120 Gt equivalent of CO 2 emitted per year in 2050. However, to achieve the 1.5 • C pathway of the Paris Agreement, the CO 2 emissions should be 0 Gt by then.

Carbon Capture (Utilization) and Storage (CCUS or CCS)
Basically, carbon capture and storage (CCS) consists of the separation and concentration of CO 2 from power generation plants or industrial processes, its pressurization and transportation, via ship or pipeline, to specific locations where it should be permanently stored deep underground, in geological formations (depleted oil or gas reservoirs or deep saline aquifers) [20,21]. This technology has been identified as a priority, being a critical emissions reduction technology that can be applied across the energy system, expecting to play an essential role in meeting the global warming targets [22][23][24].
CCS is often used interchangeably with the term Carbon Capture, Utilization, and Storage (CCUS). The difference between the two terms presented is the 'utilization' word, which refers to the use of carbon for other applications. CCUS can contribute to almost one-fifth of the emissions reductions needed across the industry sector. CCUS will play a key role in reducing CO 2 emissions from fossil-fuel-based power generation and is the only option available to reduce direct emissions from other industrial point sources significantly [25]. It was estimated that the use of CCUS would address up to 32% of global CO 2 emissions reduction by 2050 [26]. More than 28 Gt of CO 2 could be captured from industrial processes until 2060, the majority of it from the cement, steel, and chemical subsectors [27].
CCS and CCUS technologies are developed slowly, mainly as a result of high costs and unsupportive policy and regulatory frameworks in many countries [28].
The economic penalty of the capture is the crucial obstacle to CCS/CCUS implementation. The efficiency of the CO 2 capture must be increased in the capture step of the processes, as it is estimated that the capture step is responsible for 60% to 80% of the overall CCS/CCUS economic penalty [8,20]. The capture part of the process represents the main promise for cost reduction and focuses on most of the research efforts. CCS or CCUS is far from the ideal solution because it does not directly use green fuels. Still, it is the only technology capable of maintaining the utilization of the existing power plants.
In these types of processes, CO 2 capture technologies can be classified into three groups: pre-combustion systems, post-combustion systems, and oxy-fuel or oxy-combustion processes. The first and second systems depend on whether carbon dioxide is removed before or after fuel is burned. In the third, pure oxygen rather than air is used for combustion [3]. Figure 6 shows a brief scheme of methods for carbon capture. In the production processes, namely in activities related to CO 2 and other harmful greenhouse gases, even in coal power plants, it is important to reduce the emissions. For that, energy production changes as technology advances. Energy companies and industries use several technologies. This way, Industry 4.0 and the external environment force the energy companies to constantly adjust goals [2,30]. Oxy-combustion capture is still under development and is not yet commercial. Reduction of NOx, SOx, Hg emissions, and methods of exhaust gas dedusting are also important.

Pre-Combustion
In power plants, in oil, gas, and chemical industries processes, where CO 2 is produced, the pre-combustion CO 2 capture can be used [3]. Technologies that separate this gas from gas streams have been used for many decades. The main objective of the industries is CO 2 removal to meet the required downstream product specifications, whether natural gas, hydrogen, or chemicals.
In pre-combustion CO 2 capture systems, the fuel source is decarbonized before combustion. More recently, in anticipation of the requirements to limit CO 2 emissions, plants design have been improved to convert the gas produced from gasification to hydrogen and CO 2 and remove CO 2 before the combustion of the hydrogen-rich gas in the turbine [31]. The gasification or partial oxidation process combines the reacting coal with steam and oxygen at high pressure and temperature. The product is a gaseous fuel consisting mainly of carbon monoxide and hydrogen, called synthesis gas or syngas.
After this, syngas is converted to more hydrogen and carbon dioxide by adding steam at a lower temperature. This is the Water Gas Shift Reaction (WGS) (Equation (1)). Before the combustion of the hydrogen-rich gas in the gas turbine, the CO 2 is captured. The concentration can be in the range of 15-60% (dry basis/% volume), and the total pressure is typically 2-7 MPa [3,31,32]: The WGS reaction is the desired route for industrial applications, most commonly in conjunction with the Fischer-Tropsch (FT) reaction to synthesize hydrocarbon fuels from syngas. The conditions used for the FT reaction lie in the range of 200-375 • C; lower temperatures for long-chain alkanes and higher temperatures for shorter [32].
When compared with post-combustion process, CO 2 presents a higher concentration in the pre-combustion gas stream (>20% in the H 2 + CO 2 stream vs. 5-15% in a postcombustion flue gas stream). Then, CO 2 /H 2 separation is somewhat more straightforward than the CO 2 /N 2 separation in the post-combustion process due to the difference in molecular weights and molecular kinetic diameters [33]. CO 2 and H 2 can be separated using several technologies. Solvent-based CO 2 capture can be applied by chemical or physical (such as the Selexol and Fluor processes) absorption of CO 2 from syngas into a liquid carrier and regenerating the absorption liquid by increasing the temperature or reducing the pressure to break the absorbent-CO 2 bond [34]. Sorbent, membrane, and hybrid systems that combine attributes from multiple technologies are under investigation to reduce costs and energy penalties, as well as, to improve performance [35].

Oxy-Combustion
The oxy-combustion processes were designed to remove the bulk nitrogen from the air before combustion. A combination of oxygen (95% of purity, approximately) and recycled flue gas is used for the fuel combustion. A mixture with CO 2 and H 2 O is generated by recycling the flue gas, and this mixture is ready for sequestration without stripping of the CO 2 from the gas stream [36]. The flame temperature is controlled by the amount of recycled flue gas. No chemical solvent or physical sorbent is required to separate CO 2 from the flue gas due to the high concentration in the stream. The carbon dioxide rich flue gas would then be delivered by pipeline to be sequestered.
This system was developed as an alternative to the more conventional post-combustion process in coal-fired power plants. The main reason is the reduced cost of oxy-combustion when compared with post-combustion. However, although good results were obtained in laboratory scale and pilot plants, commercial plants use is still scarce [3].

Post-Combustion
Post-combustion CO 2 capture systems have been used for many decades, and in this process, the CO 2 is captured from the products of burning fossil fuels (coal, natural gas, or oil) or combustion exhaust gases. The flue gas passes through a liquid solvent, solid adsorbent, membrane, or another medium, depending on the method/technology, allowing the separation of the CO 2 from the mixture. After that, CO 2 can be transported and stored.
The drawback of post-combustion carbon capture is the low carbon dioxide concentration in the flue gases, which leads to a relatively high energy penalty and high costs of carbon capture. On the other hand, pre-combustion strives to reduce these penalties by decarbonizing the process stream before combustion, resulting in more favorable conditions and more flexible implementation, significantly reducing capture costs [37].
Several technologies can be applied for separating or capturing CO 2 from a mixture of gases in an industrial process. The purification step and the technical approach used depend on the gas stream conditions, such as temperature, pressure, and concentration, and on the product purity required.
The captured and purified gas will be transported to its final destination. In the case of CCS, a pipeline is necessary to transport captured CO 2 for a storage site. When CCU is applied, a spur on the pipeline can take a slipstream from the main flow to be diverted to the chemicals or synthetic fuels plant. At the end of the supply chain, a minor quantity of CO 2 could still be emitted or stored [38].   The most common process used to separate the CO 2 from natural gas, refinery offgases, and synthesis gas processing is absorption technology [39]. This is characterized by using a liquid/solvent that selectively absorbs CO 2 from a gas stream. Afterwards, the solvent can be regenerated through a stripping or regenerative process by heating and/or pressurization [40]. Absorption processes can be chemical absorption, used in pre-combustion or post-combustion capture, or physical absorption, primarily used in pre-combustion capture. Selexol (with dimethyl ethers of polyethylene glycol solvent), Rectisol (with methanol solvent), and Purisol (with N-methyl-2-pyrolidone as solvent) are the most common physical processes. Typical chemical solvents are primary amines such as monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP), secondary amines such as diethanolamine (DEA), and ternary amines such as methyldiethanolamine (MDEA) [39,41]. However, in this type of process, gas streams are required at high pressure. Plants for CO 2 capture with processes based on chemical absorption using MEA solvent were developed over 75 years ago to remove acidic gas impurities like H 2 S and CO 2 from natural gas streams. Afterwards, the process was adapted to treat flue gas streams, and with this technology, about 85 to 95% of the CO 2 is captured, and a product stream of CO 2 can be produced with a purity higher than 99% [42].
The major challenges for CO 2 capture from flue gases by absorption processes are the sizeable volumetric flow rates at atmospheric pressure with large amounts of CO 2 at low partial pressures (10-15% of CO 2 ) at 40 • C. Then, the process presents several disadvantages, which are the high energy consumption due to the high thermal energy required, around 4.0 GJ/t of CO 2 captured [41] (considering 30 wt% MEA and 90% CO 2 removal), the presence of SOx and NOx contaminants, and the high oxygen partial pressure, which hinders the implementation of amine absorption process [43]. Besides, it leads to corrosive product formation due to the solvents' thermal and oxidative solvent degradation.
There are many studies about processual alternatives to reduce the costs involved in power plants to reduce the operating costs. Besides the physical and chemical absorption methods discussed above, other methods could be implemented, as verified in Figure 7.
Gas separation through adsorption processes can be used in pre-and post-combustion capture and are promising alternative separation techniques characterized by solid adsorbents capable of reversibly capturing CO 2. Novel adsorbent materials for CO 2 capture with specific properties can adsorb large amounts of CO 2 to be used or stored, being these materials instruments for CO 2 utilization and storage. Adsorbents are porous solids and have a large surface area per unit mass. Each type of molecule or component creates different interactions with the adsorbent surface, leading to an eventual separation [44]. There are many types of adsorbents, which could be applied to CO 2 capture by physical adsorption processes, including activated carbons, carbon fibers, zeolites [45], metal-organic frameworks [46], and organic-inorganic hybrid materials [47,48]. The adsorbent should be chosen taking into account economic and operational criteria, which are (i) high adsorption capacity for the target gas component, i.e., CO 2 , leading to the reduction of the adsorbent quantity and process equipment size; (ii) high CO 2 selectivity, representing a high adsorption capacity ratio between CO 2 and the other components in the stream, such as, nitrogen; (iii) fast adsorption and desorption kinetics; (iv) good physical and chemical stability during the cycles and regeneration steps; (v) be regenerable by modest pressure decrease or temperature increase, leading to the minimization of the operating energy costs. Furthermore, the adsorbent should ideally also have robust performance in the presence of moisture and other contaminants that may be present in the gas stream to treat. Then, there are essential features that should be considered for a successful operation of adsorbent material, such as composition, particle size, pore size, and pore connectivity.
Cryogenic carbon capture utilizes the principle of separation based on the cooling of CO 2 to low temperature. The CO 2 is separated from the flue gas mixture after cooling this gas below −73.3 • C at atmospheric pressure. After this, CO 2 is pressurized and delivered at pipeline pressure. Cryogenic separation can be applied for post-combustion processes in two different ways. In one of these methods, CO 2 can be de-sublimated to solid CO 2 on the heat exchangers, further heated and pressurized to obtain liquid CO 2 in the recovery stage. Clodic and Younes [51] proposed this type of separation. Tuinier et al. [52] proposed another method, with the use of packed beds for de-sublimation of CO 2 . CO 2 is recovered from the packing material by feeding a fresh gas stream to increase the temperature and enhance the concentration of the CO 2 recovered from the packed bed [53]. It may be a good technique because it does not involve any additional chemicals in the separation process. However, the high compression power requirements for this method are the major disadvantage [54].
Membranes are another potential alternative to conventional solvent absorption technology. The difference in physical and/or chemical interactions between gases and membrane materials is responsible for the CO 2 separation. The method presents many advantages, such as reduced equipment size, lower energy requirements, simplicity in the process, among others. Nevertheless, in the post-combustion process, particularly in the CO 2 /N 2 separation, due to the relatively low CO 2 concentration and pressure, the driving force for membranes to perform appropriately is weak, making their implementation difficult [55].
Another potential technique for removing CO 2 from flue gases is microalgae. Microalgae are microscopic organisms that typically grow suspended in water and are driven by the same photosynthetic process as higher plants [56].
Microalgal cells are sunlight-driven cell factories that can convert carbon dioxide into raw materials for producing biofuels (e.g., biohydrogen, biodiesel, and bioethanol), animal food chemical feedstocks, and high-value bioactive compounds [56].
The ability of these cells to absorb CO 2 can be applied as an attractive alternative for CO 2 sequestration. CO 2 fixation and storage via microalgae are essentially photosynthesis, transforming water and CO 2 into organic compounds without extra energy addition or consumption and secondary pollution.
Hydrate-based CO 2 capture (HBCC) technology emerges as a potential solution for CO 2 capture from gas streaming, e.g., fromCO 2 /N 2 or from CO 2 /H 2 of fossil fuel power plants. This technology is based on the hydrate cages formation by water molecules at high pressure and low temperature, where CO 2 molecules stay enclathrated, allowing their separation. It is estimated that this technology could have a cost reduction of CO 2 capture of about 45% when compared with the chemical absorption technology [57]. Recently, studies involving hydrate-base CO 2 capture and storage have increased [58,59].

Current Progress of CCUS Facilities
Since 1972, CCS has been applied to capture CO 2 from an extensive range of sectors and industries [7]. Typically, the progress of technology development contains a series of scale-up steps: first, laboratory scale or bench; second, pilot-scale; third, demonstrationscale; fourth, commercial scale. Currently, there are eighteen large-scale facilities in operation in the world, five under construction, and twenty in various stages of development [14] (see Table 1).

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [61]. Started in 2007, Svante designed and built a CO2 capture facility to capture half a tonne of carbon per day. This technology captures carbon dioxide from flue gas, concentrates it, then releases it for safe storage or industrial use, in 60 s. Today, Svante has several industrial-scale carbon capture projects and collaborations.
Another application example is Air Products. This company possesses solutions for CO₂ capture from fossil fuel conversion before it reaches the atmosphere.

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [61]. Started in 2007, Svante designed and built a CO2 capture facility to capture half a tonne of carbon per day. This technology captures carbon dioxide from flue gas, concentrates it, then releases it for safe storage or industrial use, in 60 s. Today, Svante has several industrial-scale carbon capture projects and collaborations.
Another application example is Air Products. This company possesses solutions for CO₂ capture from fossil fuel conversion before it reaches the atmosphere. The technology has designed and constructed a large-scale system to capture CO₂ from steam methane reformers, which are located within the Valero Refinery in Port Arthur (TX, USA). Air Products has a technology that already separate, purify and transport CO₂ from natural Post-combustion amines (power plants)

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [61]. Started in 2007, Svante designed and built a CO2 capture facility to capture half a tonne of carbon per day. This technology captures carbon dioxide from flue gas, concentrates it, then releases it for safe storage or industrial use, in 60 s. Today, Svante has several industrial-scale carbon capture projects and collaborations.
Another application example is Air Products. This company possesses solutions for CO₂ capture from fossil fuel conversion before it reaches the atmosphere. The technology has designed and constructed a large-scale system to capture CO₂ from steam methane reformers, which are located within the Valero Refinery in Port Arthur (TX, USA). Air Products has a technology that already separate, purify and transport CO₂ from natural Pre-combustion NG processing

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [61]. Started in 2007, Svante designed and built a CO2 capture facility to capture half a tonne of carbon per day. This technology captures carbon dioxide from flue gas, concentrates it, then releases it for safe storage or industrial use, in 60 s. Today, Svante has several industrial-scale carbon capture projects and collaborations.
Another application example is Air Products. This company possesses solutions for CO₂ capture from fossil fuel conversion before it reaches the atmosphere. The technology has designed and constructed a large-scale system to capture CO₂ from steam methane reformers, which are located within the Valero Refinery in Port Arthur (TX, USA). Air Products has a technology that already separate, purify and transport CO₂ from natural Transport on-shore & off-shore pipelines 1 Transport ships Saline formations CCUS Notes: BECCS corresponds to bioenergy with CCS, IGCC corresponds to integrated gasification combined cycle, EGR corresponds to enhanced gas recovery, EOR corresponds to enhanced oil recovery, NG corresponds to natural gas; CO 2 utilization (non-EOR) reflects a wide range of technologies, most of which have been demonstrated conceptually at the lab scale. C-Capture; T-Transport; U-Utilization; S-Storage.

Global Facilities of CCUS
More than 30 new integrated CCUS facilities have been announced since 2007, mostly in the United States and Europe, although projects are also planned in China, Australia, Korea, the Middle East and New Zealand [60]. One of them was developed by Svante [61]. Started in 2007, Svante designed and built a CO 2 capture facility to capture half a tonne of carbon per day. This technology captures carbon dioxide from flue gas, concentrates it, then releases it for safe storage or industrial use, in 60 s. Today, Svante has several industrial-scale carbon capture projects and collaborations.
Another application example is Air Products. This company possesses solutions for CO 2 capture from fossil fuel conversion before it reaches the atmosphere. The technology has designed and constructed a large-scale system to capture CO 2 from steam methane reformers, which are located within the Valero Refinery in Port Arthur (TX, USA). Air Products has a technology that already separate, purify and transport CO 2 from natural gas reforming, management of syngas from gasification, and oxyfuel combustion in markets such as steel and glass [62].
The Global CCS Institute provides a database of CCUS facilities operating in the world. This organization establishes as large-scale integrated CCSU facilities in its database comprising the capture, transport, and storage of CO 2 at a scale of at least 800 kt of CO 2 annually for a coal-based power plant, or at least 400 kt of CO 2 annually for other emission-intensive industrial facilities (natural gas-based power generation is included). The remaining facilities and initiatives in the database are mentioned as in advancement/deployment status [63]. The last update of the database refers to October 2019.
Currently, there are several CCS facilities in Europe, and they can be classified in three different classes: (1) Commercial Carbon Capture and Storage Facilities-CO 2 can be captured and transported to be permanently stored; have economic lives similar to the host facility whose CO 2 is captured; must support a commercial return while operating and meet regulatory requirements; (2) Carbon Capture and Storage Hubs-Commercial facilities although not having a full-chain (capture, transport and storage) operation; several models are considered, combining multiple capture facilities, or CO 2 transport and storage; (3) Pilot and Demonstration Facilities-CO 2 is captured for testing, developing or demonstrating CCS technologies/processes; CO 2 captured may or may not be transported for permanent storage; A commercial return during operation is not expected.
Taking into account this classification, actually in Europe (accessed data at 1st of April 2021), there are 13 commercial CCS Facilities, two CCS Hubs (one in The Netherlands and another one in United Kingdom), and 29 Pilot and Demonstration facilities [63]. Figure 8 shows the map of the worldwide distribution of CCUS facilities, focusing on Europe.    As demonstrated with the set of works in development presented in Table 2, great efforts have been made to apply capture, storage, and utilization processes in plants. However, there are only a few large-scale CCS plants in operation in Europe so far. This is related to a series of obstacles preventing this technology from being adopted more widely. In most European countries, the nature of the challenges can be political, economic, technical, and social [64][65][66][67].

•
Political: lack of political commitment with CCS by some member states; • Economic: high investment, high operational costs, lack of competitiveness compared with other low carbon technologies; no financial compensation for the additional capital and operating costs associated with CCS; Long-term funding commitments from various public and private sources ensure the continuity of research programs which are necessary for the development of CO 2 utilization; • Technical: lack of infrastructures for transport and storage; • Social: CCS is unknown for the overall public; resistance to CO 2 storage concept; environmental risks concerning health and water pollution.
Efforts have been made to combat these barriers. As mentioned, to reach the targets defined in the Paris Agreement, immediate/prompt action would be required to reduce CO 2 emissions. Processes related to CCS can be classified as carbon-positive, near carbonneutral, or carbon-negative. Carbon positive corresponds to the majority of the processes, which still emit CO 2 for the atmosphere. Carbon-neutral and carbon-negative emissions are responsible for zero carbon emissions (neutral) and CO 2 emissions reduction to the atmosphere. Examples of the "negative" processes able to capture CO 2 are Bioenergy with Carbon Capture and Storage (BECCS) and Direct Air Capture (DAC).

Bioenergy with Carbon Capture and Storage (BECCS)
Bioenergy has always been present in the world and used by humans to produce heat. Bioenergy is used in vehicles as fuel (bioethanol) and provides electricity by burning biomass [14]. BECCS is part of the broader CCS technology and is emerging as one of the most advanced technologies to decarbonize emission-intensive industries and sectors and enable negative emissions [14]. This is a group of different technologies to produce energy from biomass and CO 2 storage. This process using biomass as a fuel source because biomass feedstock draws down CO 2 from the atmosphere through photosynthesis. Biomass is burned (combusted or converted) to biofuel, using digestion or fermentation processes. The heat generated can be used for electricity generation or industrial applications, such as cement, pulp and papermaking, waste incineration, steel and iron, and petrochemical. Conversion leads to gaseous (when digestion is applied) or liquid (when fermentation occurs) fuels production. In the liquid case, it leads to the production of bioethanol. Then, CO 2 is captured from a biomass energy conversion and permanently stored in a suitable geological formation. At the end of the process, the CO 2 emitted during bioenergy production, the CO 2 transported, converted, and utilized should be lower than the CO 2 stored to achieve the primary target-negative emissions. Figure 9 presents a scheme of the BECCS.  The Global CCS Institute (2019 data) [14] reports the existence of five facilities (one large-scale and four small-scale) actively operating using BECCS technologies worldwide. Approximately 1.5 million tonnes of CO 2 per annum (Mtpa) are captured by these facilities. Table 3 shows a description of these BECCS facilities and the planned projects. Table 3. Brief description of BECCS facilities operating today and planned projects (Notes: Mtpamillion tonnes per annum; tpa-tonnes per annum; tpd-tonnes per day).

Operating Today-Five Facilities in USA
Illinois CCS (USA)-1 Mtpa Ethanol is produced from corn at its Decatur plant, producing CO 2 as part of the fermentation process Kansas Arkalon (USA)-200,000 tpa CO 2 is compressed and piped from an ethanol plant in Kansas to Booker and Farnsworth Oil Units in Texas for EOR Bonanza CCS (USA)-100,000 tpa CO 2 is compressed and piped from an ethanol plant in Kansas to nearby Stewart Oil field for EOR Husky Energy CO 2 Injection (Canada)-250 tpd CO 2 is compressed and trucked from an ethanol plant (Saskatchewan) to nearby Lashburn and Tangleflags oil fields for EOR Farnsworth (USA)-600,000 tonnes CO 2 is compressed from an ethanol plant (Kansas) and fertiliser plant (Texas) and piped to Farnsworth oil field for EOR

Planning-One facility in Asia and Two facilities in Europe
Mikawa Power Plant (Japan) Retrofit of a 49-MW unit power plant (Omuta, Fukuoka Prefecture) to accept 100% of tonne of biomass with a CO 2 capture facility.Current situation: identify a secure offshore storage site Drax Power Plant (UK) Biomass power generation pilot (North Yorkshire): high potential to develop CO 2 capture and storage Drax Power Plant (UK) BECCS integration into waste-to-energy and a cement plants: Plant: plans to capture 400,000 tpa of CO 2 (Klemetsrud waste-to-energy)Currently co-fires up to 30% biomass and plans to capture up to 400,000 tpa of CO 2 (Norcem Cement plant) CO 2 will be sent to a storage site (Norwegian North Sea) from waste-to-energy and cement plants Note: Mtpa is million tonnes per annum of CO 2 ; tpa is tonnes per annum of CO 2 ; tpd is tonnes per day of CO 2 .

Direct Air Capture (DAC)
Industrial applications containing air capture technology are not new and have existed since 1930 [68].
In contrast to carbon dioxide capture from sources, such as cement or biomass plants, direct air capture (DAC) is a technology that captures CO 2 directly from the ambient air and generates an enriched stream of CO 2 for storage or use. The process can be denominated as physical or chemical separation. Figure 10 presents a scheme of the DAC process. It is common to divide the DAC process into three different classes, regarding the approach to separate CO 2 from the air: chemical, cryogenic, and membranes [70].
Two technology approaches are being used to extract CO 2 from the atmosphere in the chemical systems: liquid systems (liquid solvents) and solid systems (solid sorbents) direct air capture. In the cryogenic processes, CO 2 is removed from the air by freezing as a by-product of cryogenic oxygen separation. Membranes are used to separate CO 2 from the air and seawater. Chemical systems are the preferred processes of DAC used by companies.
Liquid systems pass air through chemical solutions, which removes the CO 2 while returning the rest of the air to the environment. For example, a typical process used is when sodium hydroxide is the solvent applied (used in the pulp and paper industry). CO 2 reacts with sodium hydroxide (NaOH) and precipitates sodium carbonate (Na 2 CO 3 ), which produces a highly pure gaseous CO 2 stream when heated; after that, sodium hydroxide is recycled from sodium carbonate.
The reaction occurs between NaOH and CO 2 , as presented in Equation (2): This process has a high potential to obtain high loadings of CO 2 over a wide range of operating conditions and system designs because of the strong binding energy associated with the reaction presented in Equation (2). A disadvantage is the high energy requirements for releasing the CO 2 during the regeneration stage [20]. Figure 11 shows a brief scheme of this process. Figure 11. Brief scheme of a liquid solvent process used for capturing CO 2 from air, using NaOH as the absorber (adapted from Mazzotti et al. [71]).
Solid direct air capture technology makes use of solid sorbent filters that chemically bind with CO 2 . When the filters are heated, they release the concentrated CO 2 , which can be captured for sequestration or utilization.
However, CO 2 in the air is approximately 300 times (~400 ppm) more dilute than in flue gas from a coal-fired power plant, which results in a costly process to separate CO 2 with the same end purity as the one obtained in the CO 2 captured from fossil fuel power plants [72]. Figure 12 shows a brief scheme of the DAC process.
At present, few companies are involved in the DAC field, all designing or using different technologies of DAC, and different markets are focused. Carbon Engineering Ltd. (CE, Vancouver, BC, Canada) uses liquid alkali metal oxide sorbents regenerated by heat at around 800 • C. CE uses natural gas to power its machines, co-capturing CO 2 from the flue gas stream of the burned natural gas in addition to atmospheric capture [74,75].
Global Thermostat (GT, New York, NY, USA) is a US company which uses a solid amine-based sorbent material for CO 2 capture from air, regenerated at around 80-100 • C [76].
Also, using DAC design, Climeworks AG (Zurich, Switzerland) capture CO 2 with a system based on an adsorption-desorption process with alkaline-functionalized adsorbents. The adsorption is performed at ambient conditions while the desorption occurs using a temperature-vacuum-swing (TVSA) process. The pressure decrease and the temperature increase from 80 to 120 • C, allow to release the CO 2 [76]. The enriched stream of CO 2 is produced at 1 bar with a purity of >99.8%. If the relative humidity on the feed is high, the H 2 O is also extracted from the air as a by-product [77]. The first commercial DAC plant was presented in 2017 in Switzerland from Climeworks, with a capacity for 900 t of CO 2 captured per year from the air.
Currently, in Europe, in the United States (US), and in Canada, there are more than 15 DAC plants operating worldwide, most of them are small and sell CO 2 captured for use (in carbonated drinks, for example). However, the first large-scale DAC plant has been developed in the US by a Carbon Engineering Ltd. and Occidental Petroleum partnership. The plant will capture up to 1 MtCO 2 (metric tonnes of CO 2 ) per year for EOR. This unit could become operational as early as 2023 [76]. Table 4 presents the companies that are working to commercialize DAC systems nowadays.
Several studies have been presented with direct air capture applications to obtain climate change mitigation, some more optimistic than others. Creutzig, et al. [78] estimates that DAC will reach 1 Gt of CO 2 per year in 2050. Fasihi, et al. [79] presents an estimative of about 7 Gt of CO 2 captured per year in the energy system, and about 8 Gt of CO 2 captured per year in carbon dioxide removal in the same year.
Today, the costs involved in direct air capture systems are approximately 510 € per tonnes of CO 2 captured [80].
The transition to a net-zero energy system, in which the amount of CO 2 released to the atmosphere is equivalent to the amount being removed, is highly dependent on the carbon removal processes. The application of decarbonization strategies in the several sectors as aviation and heavy industry would be very difficult. In these cases, carbon removal technologies can be the key for an effective transition. In the 2030 Sustainable Development Scenario, it was defined that CO 2 capture by direct air capture should reach almost 10 Mt of CO 2 per year (in 2030) [76].

Industrial Processes
Industrial processes are responsible for raw materials conversion into useable products, which results in energy consumption and CO 2 emissions. For this conversion, fossil fuels continue to satisfy most of the industrial energy demand. However, these processes can be transformed to meet global climate changes. The industrial CO 2 emissions can be categorized into four main groups [27]: • Energy-related emissions: combustion of coal, oil, and natural gas (considering biomass with an emission factor of zero); • Process emissions: associated with chemical and physical reactions, such as the production of aluminum, ferroalloys, lubricants and paraffins, and fuels through coal and gas-to-liquid processes, etc.; • Direct emissions: all emissions associated with industrial processes, except the electricity, heat, and steam purchases (energy-related emissions plus process emissions); • Indirect emissions: all emissions "out of the facilities", including electricity, heat and steam purchased.
Industry is responsible for about one-quarter of CO 2 emissions from energy and industrial processes, being 90% of the direct GHG emissions from industrial production, and 40% of global energy demand, especially in cement, in iron and steel and in chemicals industries, which are the most challenging for emissions reduction. Between 1990 and 2017, industrial CO 2 emissions increased 70%. According to Clean Technology Scenario (CTS), consistent with the Paris Agreement defined targets, more than 28 Gt of CO 2 must be captured from industrial facilities until 2060 [27]. CCUS can be a critical factor in the industry decarbonization action. CCUS technologies will contribute to a reduction of 21 Gt of CO 2 of emissions (27%) in the period of 2017-2060, from the cement (18%, capturing 5 Gt of CO 2 ), iron and steel (15%, capturing 10 Gt of CO 2 ), and chemical subsectors (38%, capturing 14 Gt of CO 2 ) [27].
Several industrial sectors produce CO 2 at different temperatures, concentrations, purities, pressures, and volumes, and for all of them, carbon dioxide capture technologies could be applicable. This will be vital for energy-intensive industries, such as those listed below to capture carbon if the EU is to reach its climate targets. These industry subsectors consider iron and steel, chemicals and petrochemicals, cement, pulp and paper, aluminium, and other industries such as ceramics and glass production.
The costs involved in CO 2 capture vary greatly by point source and by capture technology. Costs range from 15 USD per tonne of carbon dioxide (USD/t of CO 2 ) to 60 USD/t of CO 2 for concentrated CO 2 streams (e.g., natural gas processing and bioethanol production through fermentation), or from 40 USD/tCO 2 to 80 USD/tCO 2 for coal-and gas-fired power plants. The costs can be over USD 100/t of CO 2 for smaller or more dilute point sources (e.g., industrial furnaces) [27].
The current status of industrial sectors is encouraging. Several works are in development today, especially involving the CO 2 capture from high -purity CO 2 sources.

Conclusions
International climate obligations, especially the values established in the Paris Agreement, require detailed monitoring and reporting of greenhouse gas emissions, which allowed to observe the increase of CO 2 emissions over time. These scary numbers allow understanding the immediate need to act to reduce the emissions. In this regard, CO 2 capture, utilization, and storage have demonstrated a high potential to be used to reduce global warming potential from power plants. CCS/CCUS has many challenges to overcome. For that, continuous advancement of knowledge is essential to improve the economic and environmental feasibility and technologies potential. As can be seen, several projects are under study to improve the capture of CO 2 and utilization/storage. In the future, some technologies may offer a range of potential opportunities for a sustainable global industry, supporting the climate change objectives, the circular economy, renewable energy deployment, the evolution of CO 2 capture systems, among others. With the 1.5 • C pathway of the Paris Agreement, CO 2 emissions should be 0 in 2050. Therefore, there is still a long path ahead.   Initiate a low cost full chain CCS project in the North East of Scotland; cluster of capture, transport and storage infrastructure; CO 2 is separated from natural gas and vented, adjacent to an offshore transport pipeline, which connects to a well understood offshore basin, rich in storage opportunities Designed by Axens, started in 2020 at the ArcelorMittal steelworks site in Dunkirk; able to capture 0.5 metric tonnes of CO 2 an hour from steelmaking gases by 2022 Consisted of an initial oxy-fuel technology mapping phase followed by testing of a 40-MWth oxy-fuel burner at Renfrew, Scotland, under realistic operating conditions and included testing adaptation from air-firing to oxy-fuel firing on pulverized coal; the pilot facility completed 20 test days