1. Introduction

Global CO 2 emissions reached 36 gigatons (GT) in 2017; this translates to a loss of nearly 10 tons of carbon to the environment ^[1]. By 2050, there will be a profound transformation in carbon economics, spurred on by the desire to reduce carbon dioxide emissions and reuse the same in a wide range of advanced industrial processes that use modern technologies and artificial intelligence. All industries, especially those that consume a large amount of energy, must include low-carbon options, such as gaseous fuels and others ^[2]. However, there are two sides to this debate. One side argues that there is no relationship between global warming and CO 2. They think that measuring the effect of human activity on the climate is difficult and complex, and they cannot reconcile with the notion that CO 2 is a primary contributor to global warming ^[3]. The other side argues that CO 2 is the main reason for global warming. Studies show that the carbon dioxide levels in the atmosphere have increased since the beginning of the Industrial Revolution. However, what is the rate of warming that might arise due to the increased CO 2 concentration in the air? Natural experiments, based on real-world observations, indicate that global warming of no more than a few tenths of a degree can result from such an increase in carbon dioxide ^[4]. Recent research also shows that methane emissions outpace the impact of carbon sinks from trees in wooded wetlands ^[5].

Deforestation hurts the climate; this is evident in the worsening deforestation rates in the Amazon rainforest. In 2019, 10,129 km 2 of forest cover was cut. Unfortunately, the deforestation rate continued to grow by 9.5% in 2020, compared to the previous year ^[6]. Carbon stocks remaining in humid tropical forests are currently at risk of human deforestation, and there is a potential for these stocks to be released due to climate change Moreover, continued tropical deforestation will play a massive role in accumulating greenhouse gas concentrations in the future ^[7]. Tropical forests are a significant factor in stabilising carbon dioxide in the climate. As tropical forests greatly benefit the ecosystem, it is unfortunate that they are lost for unsustainable benefits. The actual loss is when environmental degradation remains over the years. Despite the constant prohibitions against deforestation and logging, only 12% of the original tropical forest cover remains; thus, the remainder of these forests must be preserved ^[8].

Between 1984 and 2016, 45,945.08 km 2 of vegetation cover was lost in Northern Nigeria. Bare land increased by 28,293.07 km 2, and the built-up area also increased by 11,422.48 km 2 within the same time ( Figure 1 ). The massive increase in the barren lands is associated with the intense creep of desert sand. Sand traps the incoming solar radiation during the day, which leads to a rise in the heating of the Earth’s surface. This, in turn, imposes extremely austere conditions that lead to the deterioration of the abundance of vegetation ^[9]. The circular carbon economy (CCE) is an integrated system that leans on reducing CO 2 emissions and manage them through an environmental and economical integrated management system that works on modern technologies ^[10]. The circular carbon economy (CCE) system achieves a balance by closing the carbon circle, capturing CO 2 emissions, and using them economically after their initial linear use ^[10]. This approach differs in that it does not focus solely on reducing or avoiding the increase in the amounts of carbon. The steady increase in carbon dioxide levels requires increased effort to mitigate their impact ^[11]. Carbon dioxide is sourced either naturally or through human intervention ^[12]. There are many uses for carbon dioxide; it can be used immediately after its capture or after being chemically reacted. These uses are considered to be the actual seizure of carbon dioxide, since they exploit carbon dioxide emissions for valuable materials. CO 2 capture and storage (CCS) effectively reduce carbon dioxide emissions ^[13].

Figure 1. Spatial variation and temporal changes in land cover are shown throughout the study from 1984 to 2016. Adapted with permission from Elsevier Ref. ^[9].

There are many techniques for removing carbon dioxide ^[14][15] that will be discussed from a technical and economic point of view, as well as the existence of masses of research methods that deal with the uptake and utilisation of carbon dioxide sequestration; however, the issue of taking advantage of carbon emissions, recycling and benefiting from them, and looking at carbon emissions from an economic perspective are topics that need more studies and research. Therefore, this article attempts to treat the subject from a holistic view and draw a roadmap for further research and studies in this field.

2. The Circular Carbon Economy (CCE)

Reduce: Use pathways that reduce carbon emissions. For example, energy efficiency, in terms of both supply and demand, reduces energy consumption and the associated carbon. Likewise, carbon-neutral energy supply options, such as non-biotic renewable sources and nuclear power, reduce the flow of carbon into the system as well. However, they can indirectly lead to carbon emissions during its manufacture, construction, and installation.

Reuse: Carbon capture and utilisation mean that CO 2 does not chemically react to manufacture-enhanced or enhanced oil recovery material. In this context, the experience of the Saudi Basic Industries Corporation (SABIC) is considered a pioneer in storing and recycling carbon dioxide in the industry, to produce fertilisers and methanol, with 500,000 tons of carbon dioxide recycled each year ^[16].

Recycle: Chemical reactions conducted on carbon can convert it into new economically beneficial substances. Recycling is represented in the natural carbon cycle as natural sinks, such as plants, soil, and oceans, which pull CO 2 out of the atmosphere and then rerelease it through decomposition and combustion. Thus, carbon is recycled efficiently, and the bioenergy subsystem is considered zero-emission. As a result, an equivalent of biomass grows to replace what is consumed as biological raw materials, such as wood, fuel crops, and algae bioenergy.

Remove: Remove carbon from the system and store it either directly or from natural sources. This method is the most effective. The captured carbon can be converted into raw materials in “reuse” or removed by storing it through chemical or geological methods. CO 2 can be directly captured from industrial processes and combustion points, and it can also be captured directly from the air using direct air collection techniques. Also, land can be managed to become a natural sink for carbon in the atmosphere. Natural sinks, carbon capture and storage, bioenergy, and direct air harvesting can all close the loop of emissions elsewhere, in areas that may be difficult or too expensive to capture such emissions directly, such as from jet fuel combustion ^[8][17][18]. The economic importance of the carbon circle is limited to reducing carbon dioxide emissions and producing products with economic value.

3. The Application That Involves CO2 and Its Economic Impact

Carbon capture, utilisation, and storage (CCUS) emissions of chemical plants will eliminate 3.5 gigatons of carbon dioxide annually by 2030 ^[19]. It is possible to use CO 2 in many products, with economic and beneficial returns in various chemical and biological fields, such as in food and other technologies. This will achieve the required climate change goals in a valuable and intelligent way ^[20][21][22]. For example, carbon dioxide is consumed in oil and gas manufacturing, enhanced oil recovery, food production, plant growth stimulation, manufacturing processes, etc. ^[21]. The use of carbon dioxide in these technologies reduces carbon dioxide emissions by 13% when compared to use in energy, fuel, and industrial conversion, as demonstrated in Figure 2 . The production of chemicals, cement, and steel accounts for 60% of the total industry sector’s production ^[23].

Figure 2. Ratios of carbon dioxide consumption to its uses.

Carbon dioxide can be used in the production of many chemicals. Table 1 shows the amount of carbon dioxide consumed in producing some chemicals, along with their economic cost. The urea industry is the largest consumer of carbon dioxide in chemical production, consuming 130 gigatons of a total of 230 megatons of carbon dioxide per year ^[23]. Carbon dioxide reacts with ammonia at temperatures between 185 and 195 °C, to produce urea, which is distinguished as an agricultural fertiliser involved in the creation of some medicines and chemicals ^[24]. Many value-added materials can be produced on the market in fuel production, such as methane, methanol, gasoline, and engine fuel ^[21]. Two thousand gigatons of carbon dioxide per year are consumed in fuel production; this is considered a very high percentage ^[25]. In the production of enhanced oil recovery, carbon dioxide is used immediately after capture. As a result, 70–80 gigatons per year of CO 2 are consumed.

There are several uses of carbon dioxide in food production, one of which is as a coolant to preserve food and drinks, while another is the production of dry ice, which has a greater cooling capacity than water ice ^[28]. In addition, carbon dioxide has recently been used as a packaging gas in the food industry, preserving fresh products and freshness for meat, fish, and pre-packaged food products, by controlling their biochemical metabolism ^[29]. Carbon dioxide production from ammonia was found to be higher than any other chemicals that use carbon dioxide, as demonstrated in Table 2 .