Carbon capture and usage technologies

Introduction

The fourth industrial revolution has engaged a swift pace of change that has disrupted businesses and society. The radical change in the way of work and life demands keeping up with technological change. The continuous expansion of the industry results in the emission of greenhouse gases with adverse impacts on climate change. According to research, Carbon dioxide (CO2) is the main gas and contributor to the greenhouse effect. It accounts for more than 70% of the global greenhouse gases, and with the intensified CO2 emissions, a series of problems have emerged that have provoked human concern. It has, therefore, become critical for manufacturers to find effective strategies to address the problem caused by CO2. With CO2 as a greenhouse gas and a potential carbon resource, how to capture and effectively use it is an essential aspect of the study. This paper offers a profound analysis of the carbon capture, and utilization technologies, their advantages and disadvantages.

Carbon Capture

Carbon capture and Usage technology provides a way to mitigate and adapt to climate change. It refers to a way of reducing CO2 from the emission sources such as industrial facilities and power plants. The process involves the removal of a relatively pure form of CO2, separation, treatment, and transportation to a long-term storage location, usually a geological formation. The emissions are captured at the source before they are released into the atmosphere. The technology captures CO2 from industrial processes and injects it deep underground to reduce emissions. The gas can also be incorporated into different types of products, such as chemicals, synthetic fuels, and concrete.

The rationale of Carbon capture technology is that it provides a unique way to reduce emissions. The technology can reduce emissions from the source and the existing CO2 in the atmosphere.   Through the technology, CO2 can be captured in the production process, converted, and used in different ways. The process not only enhances storage but also realizes recycling and reuse of CO₂ in a more practical way that provides economic benefit. The removal of CO2 at a large scale provides a relatively effective method to alleviate the greenhouse effect. The development of the technology using a wide-based strategy will ensure long-term stability and exploit its great potential.

Carbon Capture and Usage (CCU): How it works

CCU is a combination of technologies designed to prevent the release of CO₂ generated through industrial processes and conventional methods of power generation into the atmosphere. Instead, the technologies inoculate the CO₂ into appropriate underground storage reservoirs. The technology thus works by separating the CO₂ emissions from the process, compressing and transporting the CO₂ into identified underground storage locations and injecting it. Suitable methods of transporting the C0₂ have been identified through pipelines and shipping. Geological locations termed appropriate for storage of CO₂ are abandoned gas and oil fields, unmineable coal seams, and deep saline formations. The deployment of CCU in power generation and industrial plants is critical due to its role in reducing emissions. The technology allows continued use of fossil fuel through its substantial decrease in emissions.

C0₂ Capture Technologies

There are various technologies used in capturing, transporting, and geological storage of CO_2. Global analysis of Carbon dioxide capturing indicates an increase in CCU projects at the global level. According to the CCUS project Explorer Reports, there are currently 40 operational CCUSs, 25 are under construction and more than 300 are in the planning stages. The reports also show that the operational units capture between 42 and 49 million metric tons of CO₂ every year. Upon completion of all projects in the development stages, the report projects that a total capacity of 360 metric tons of C02 per year will be achieved, which translates to 0.7% of the current global greenhouse gases.

The operational projects are based in North America, which has the leading projects. Middle East, Europe, and other regions have a handful of projects with announced and planned projects in East Asia and Australia. However, to reach the envisioned Net Zero emissions, the Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency estimate that the CCU will contribute 6% of the mitigation and help reach the Net Zero by 2050 if the current economic, technological, and sociocultural barriers are eliminated.

Major Carbon Capture Technologies

The technologies employed in the capture, transportation, use, and storage adopt different forms. Research and development aims to improve the technologies and advance the process of separation of CO2 from other compounds that are emitted during the industrial process. The technologies used in the capture process are grouped into three main categories: post-combustion, pre-combustion, and oxyfuel combustion. Each approach is shaped by the industrial process and the type of power plant the process is taking place.

1. Pre-combustion Method

In the pre-combustion carbon capturing method, the primary fuel in the combustion process is mixed with steam and air or oxygen. It converts into a mix of carbon monoxide and hydrogen. In a shift reactor, the carbon monoxide gas is converted into CO2, which is then separated. Hydrogen is used to generate power and heat. The pre-combustion carbon capture method has been found suitable and applied in integrated gasification combined cycle plants. However, the pre-combustion method requires appropriate materials and specific conditions to meet the high-temperature requirements for the processes to take place. As a result, the development of the method is relatively low compared to others.

1. Post Combustion

The method is widely accepted and used and can be considered as a mature technology in the industry. The method has demonstrated a high capture efficiency and good CO2 selectivity through its various techniques. The method removes C02 from flue gas as a result of the combustion of a fossil fuel. The separation process involves the use of a solvent that captures the CO2. The capture techniques include chemical absorption, use of a membrane, adsorption, cryogenics, hydrate, and microbial.

Chemical absorption

In the chemical absorption process, a chemical solvent-weak alkaline solution is used to react with the C02. The process generates compounds and carbon dioxide undergoes adsorption-attached to the surface of the compounds. The CO2 then undergoes desorption- released from the compound surface through a change in the eternal conditions and temperature of the process. The chemical absorbents used in carbon capture include ammonia solution, sodium hydroxide, and the organic amine solution. The amine solution is the most effective absorbent and is widely used.

Adsorption

The process involves the use of a solid-phase porous material. The process employs the van der Waals force between the porous solid adsorbent and the CO2 adsorbent to separate and capture CO2. The method has a high adsorption capacity and is preferred due to the low regeneration cost, lack of corrosion, and low consumption of energy. Ideal adsorbents are considered those with high adsorption capacity and selectivity for CO2. Other adsorbent materials include activated carbon, Zeolite, geopolymers, and hydrotalcite. Research has shown that as a carbon capture method, adsorption demonstrates a CO2 recovery of 72% and purity of 89.7%, making it a viable technology that should be further exploited.

Membrane Separation

It involves the separation of gases under pressure facilitated by differences in permeation rates of various gases. In CO2 capturing, inorganic membranes are used instead of polymer membranes due to their ideal CO2 selectivity. The inorganic membranes are also better in stability resistance to corrosion and have a higher separation performance and, thus, more suitable in the carbon capturing process.

Cryogenic Separation

A process through which solid CO2 is separated from the gas mixture. It involves desublimation under low temperatures in a physical separation process. The process can be used to melt solid CO2 and recover it in the form of a high-purity liquid that is convenient for injection into underground storage and use. The method results in the acquirement of high-purity CO2, and its concentration is also high, making it a suitable method of separation. It, however, consumes much energy and is suitable for cases of high CO2 concentration, which can discourage its use.

Hydrate Method

It is a gas separation technology that involves the formation of a cage-shaped crystal envelope as a gas hydrate. The cage is formed from a selective combination of hydrogen and water to form a bond. The method works under the principle of great pressure difference. As gas hydrates are formed, the components with low pressure are enhanced in the gas hydrate phase, while those with high pressure are left in the reactor. The result is a separation of the mixed gases. The method is characterized by a lack of corrosion, lack of pollution, low energy consumption, and a simplified process, making it suitable for carbon capture.

Microbiological Method

The microbial method involves the use of microorganisms in the capture of C02. The method entails the application of the photosynthesis process of absorbing and fixing C02 in plants. The microorganism’s principle allows a direct conversion of CO2 into organic matter. It is used due to its low energy consumption, lack of corrosion, and enhancing green environmental protection. Microbial carbon storage has a capacity of reaching seven billion each year which makes it an effective method to improve climate change globally. As an emerging carbon capture method, it has been accepted due to its utilization of the green environmental protection concept.

1. Oxy-Fuel Combustion

The method is used in capturing carbon dioxide by combusting the primary oxygen instead of air. The combustion process produces a flue gas containing water vapour and a high concentration of carbon dioxide approximated to be 80%. The flue gas is cooled to condense the water vapour, leaving a high concentration and pure CO2 stream. The method is, however, not commonly used due to the requirement for certain conditions to be met to produce the high temperatures required. The method also demands the use of additional equipment for the extraction of oxygen from the air.

The Use of Carbon Capture Technologies

The separation technologies can be used in various industries such as natural gas processing, steel, cement and in the production of Ammonia. The C02 capture technologies are also used in primary industries where large amounts of CO2 are produced. Research shows that industries that deal with iron, steel, cement and chemical industries produce large amounts of CO2 due to the consumption of fossil fuels for their operations. The most widely used carbon capture method is the chemical absorption method. Carbon capture technologies have vastly improved the carbon capture rate with significant reduction of emissions with their various advantages and disadvantages and the ability to combine different technologies for use. The use of the technologies is in line with the effort to achieve net zero emissions by 2050. Carbon capture technologies can successfully capture 85%-95% of all C02 gas produced. After successful capturing of the gas, it is then transported to suitable locations for storage, such as uninhibited gas and oil fields in deep saline formations with sufficient temperature and pressure to keep the C02 in a liquid state.

Utilization of Captured CO2

After capturing C02, a large number of projects have been launched around the world for storage. However, high uncertainty and cost of storage have increased the preference for technologies that allow CO2 to be reused. According to research, storage of C02 in underground geological locations faces a potential challenge of leakage. It has also been found that high amounts of CO2 increase pressure that can cause small earthquakes. However, a comparison of CO2 storage and utilization shows that reusing C02 cannot permanently remove the gas from the atmosphere and hinders the achievement of harmful emissions as envisioned. The use of CO2, however, plays a critical role in addressing the problem of C02. Resource utilization of CO2 is therefore common in the following aspects.

Physical Utilization

CO2 is mainly used physically in refrigeration for the storage of food and in petroleum and other industries. In most cases, except in carbon flooding, the physical use of CO2 delays its release, but it is eventually released back into the atmosphere. Therefore, the physical utilization of CO2 does not sequester it from the environment and cannot be considered as a decarbonization technology. The physical use of C02 has economic benefits as it lays the foundation for its future use in capture and storage projects. Some of the common physical uses of captured CO2 include use in beer and carbonated drinks, preservation of fresh frozen food, C02 gas-shielded welding, and C02 flooding, where C02 is inoculated into a formation to increase oil flow and recovery. Other uses include its use in the process of expanding shredded tobacco, use of CO2 as a cleaning agent, use in fluid extraction, and as a fracturing medium in unconventional oil and gas reservoirs.

Chemical Use

CO2 is an essential raw material in the chemical industry. It is mainly used as a reactant in chemical reactions that produce urea, salicylic acid, organic acids, hydrocarbons, and polyesters. However, like in the physical use of CO2, the chemical products produced using CO2 are oxidized, fostering C02 emission into the atmosphere. The main uses of CO2 in chemical industries include the production of synthetic bulk chemicals such as methanol and formic acid. It is also used in the production of synthetic polymer materials, such as polycarbonate and polyurethane, used in the manufacturing of foams and sponges,

Biological Use

C02 is used in biotechnology in the process of designing new artificial photosynthetic systems. In bio-utilization, CO2 is used in the simulation of the photosynthesis of plants or microorganisms in nature and converts them into different products of high value. The primary use of CO2 in bio-utilization is in the conversion of plant aerosol fertilizers and biofuels. The use of CO2 in photosynthesis is a direct way of using the gas with high effectiveness and sustainability. It promotes plant growth, increases plant yields, and is simple and cheap to operate. The amount of CO2 released determines the process with high concentrations offering better growth. Carbon Sequestration by microalgae to produce biofuels is also an attractive option for using CO2 in bio-technology.

Mineralization Use

In the mineralization process, CO2 is used to form carbonate precipitates. It is used in direct and indirect mineralization. In direct mineralization, C02 is used to facilitate weathering such that the mineralized raw materials react with CO2 to produce valuable products that can be sold. In indirect mineralization, a chemical is added to convert mineralized raw materials into intermediate products. CO2 is used to improve the reaction rate, and different high-value products are obtained.

Conclusion

Carbon capture and usage is one of the many ways being used to address climate change and reduce emissions. The technologies are mainly used in power plants and industries, especially those that specialize in the production of cement, steel, and chemicals. There has, however, been a slow adoption of carbon-capturing technologies due to fear that they perpetuate the use of fossil fuels, which have adverse health and social impacts. Addressing the various challenges in CCU and enhancing responsible deployment of the technology will make them effective at reducing emissions, which will benefit humanity and the environment. The full benefit of carbon capture technologies can only be realized through strong governance and implementation of the regulatory framework that will place the technologies where they should be to reach climate goals. The use of CCU and plans to implement it should engage the local community to help understand the communal perspectives on the project and share information on the expected environment and health impacts as well as the benefits.