**2. Carbon Dioxide Employment**

*2.1. CO2 Management—Obligation and Opportunity*

The first motif of CO2 managemen<sup>t</sup> results from the regulations, e.g., of the European Union [11]. Because a positive balance of emission is related to high financial penalties, the possibility of reducing emission is attractive in economic terms. Table 1 presents the CO2 emission for selected economies of the European Union countries.

**Citation:** Lach, D.; Polanski, J.; Kapkowski, M. CO2—A Crisis or Novel Functionalization Opportunity? *Energies* **2022**, *15*, 1617.https://doi.org/10.3390/ en15051617

Academic Editor: Wasim Khan

Received: 28 December 2021 Accepted: 19 February 2022 Published: 22 February 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

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**Table 1.** Reduction of greenhouse gas and carbon dioxide emissions in selected countries of the European Union (UE). Own study based on data from [11–15].

Greenhouse gases (GHG) emission reduction by 2030 as against this emission in 2005 [11]. 2 Greenhouse gases (GHG) emission in 2005 based on [12]. 3 Averaged value of CO2 share in greenhouse gases (GHG) based on the UNFCCC (2017) [13] and IPCC (2014) [14] data.

As the most recent regulation on greenhouse gases (GHG) emission reduction [15] stipulates, the European Union member states shall reduce the GHG emission in the years 2021–2030, depending on the country, from 0 to 40% below the 2005 level. Carbon dioxide is the dominating component of greenhouse gases. Depending on the source, its share ranges between 65% and 81% [13,14].. In the near future one should expect the economy to be subordinated to the EU requirements and based on so-called smart carbon footprint managemen<sup>t</sup> [16–21].

The second motif results from the size of the share of individual emission sources. The highest CO2 emission is now related to the industry, namely power plants, oil and gas processing, cement production, iron and steel metallurgy, or petrochemical industry [10,22,23]. Figure 1 presents the percentage share of individual industry sectors in their total annual carbon dioxide emission.

**Figure 1.** Percentage share of selected industry sources in their total annual CO2 emissions in the European Union. Data for 2019, extracted from [24].

The anthropogenic impact of carbon dioxide emissions offers a grea<sup>t</sup> opportunity for using CO2 as a raw material or even a feedstock wherever it is currently treated as pollutant or waste. Relatively pure carbon dioxide may be recovered from the production of hydrogen, ammonia, ethylene oxide, gas processing, natural gas liquefaction, hydrocarbons production in the Fischer-Topsch process, or biorefineries, e.g., from ethanol production [20,25]. Such technologies provide a possibility to expand simply the existing plants with units for CO2 conversion to products useful on the chemical market. Carbon dioxide is now used in the synthesis of urea, salicylic acid, or pigments [10]. In addition, two basic product types may be distinguished, in which CO2 plays the role of the main raw material. The first type includes inorganic or organic products, the structures of which contain the entire motif of CO2 molecule. The second type comprises products formed in reactions, in which C-O bonds are broken. This division is of key importance in terms of energy balance and application. The first type of reaction (both inorganic and organic)

is not energy-intensive [26] and can frequently proceed spontaneously (at unfavorable kinetics), as in the production of inorganic carbonates. In the case of the second product type, the breaking of C-O bond is energy-intensive and requires the application of reducers, e.g., hydrogen. In the context of smart managemen<sup>t</sup> of carbon dioxide balance [16–21] it is important that the energy necessary for such reaction would originate from renewable energy sources (solar, wind, geothermal, etc.) or at least from sources different than coal (e.g., nuclear energy). Otherwise, the balance of CO2 conversion will be reduced by the amount of CO2 emitted in the process of energy generation, used to carry out the reaction. It is also necessary to remember such factors as the blocking (storage) time of CO2 molecules in the product. Attention was drawn to this in the report of the Intergovernmental Panel on Climate Change (IPCC) on the capture and storage of carbon dioxide [27]. A long period of use of a product formed from carbon dioxide will block CO2 for a longer period of time, in this way preventing the reintroduction of carbon dioxide to the atmosphere. In relation to this the first type of product is more stable, e.g., inorganic and organic carbonates, and ensures long-term (from decades to centuries) immobilization of CO2, while the second type (e.g., fuels or chemicals) immobilizes CO2 usually for periods of months to a few years. As the second type of product over years may be subject to several cycles of processing and CO2 releasing (depending on the product life), with the use of renewable energy sources, such technologies are at least equally as attractive as the CCS (carbon capture and storage) technologies [16].
