The Carbon Dioxide Revolution: Challenges and Perspectives for a Global Society

By Michele Aresta and Angela Dibenedetto

This book focuses on carbon dioxide and its global role in our everyday life. Starting with society's dependency on energy, it demonstrates the various sources of carbon dioxide and discusses the putative effects of its accumulation in the atmosphere and its impact on the climate. It then provides an overview of how we can reduce carbon dioxide production and reviews innovative technologies and alternative energy resources. The book closes with a perspective on how carbon dioxide can be utilized reasonably and how mimicking nature can provide us with a solution. 

Using simple language, this book discusses one of today's biggest challenges for the future of our planet in a way that is understandable for the general public. The authors also provide deep insights into specific issues, making the book a useful resource for researchers and students.

• Language: English
• Publisher: Springer
• Release date: Jan 4, 2021
• ISBN: 9783030590611

Book preview

© Springer Nature Switzerland AG 2021

M. Aresta, A. DibenedettoThe Carbon Dioxide Revolutionhttps://doi.org/10.1007/978-3-030-59061-1_1

1. Energy and Our Society

Michele Aresta¹   and Angela Dibenedetto²  

(1)

LAB H124, Tecnopolis, Innovative Catalysis for Carbon Recycling, Valenzano, Bari, Italy

(2)

CIRCC and Department of Chemistry, University of Bari Aldo Moro, Bari, Italy

Michele Aresta (Corresponding author)

Email: [e-mail]

Angela Dibenedetto

Email: [e-mail]

Abstract

Fossil-C, in the form of coal, natural gas, and oil, covers 81+% of the energy necessary to satisfy the needs of our society. The continued use of fossil-C causes the accumulation of carbon dioxide in the atmosphere. The reduction of the emission of CO2 is becoming urgent.

1.1 Introduction

Humans, as all living organisms, emit bio-CO2 during the expiration (ca. 0.9 kg/day‧person, or 328 kg/y‧person, or ca. 25 t/person in a life of 75 y). Therefore, over 7 billion people in the actual world population emit ca. 7 MtCO2/day or 2.55 GtCO2/y just for the life’s very basic operations such as respiration.

Since man uses fire, it has also become an emitter of CO2 produced through the combustion of fuels in a variety of activities, including cooking. During 2018, the total World Energy Consumption (WEC) was of 13 978 Mtoe (Mtoe = million-ton-oil-equivalent, i.e., expressing all the energy used as oil), [1] continuing the growth observed over the last 28 years (Table 1.1).

Table 1.1

Total energy consumption as Mtoilequivalent and its segmentation per areas on earth

Note Only CIS has apparently shown a decrease of energy consumption (figures in parentheses) over the period 1990–2018 during which a variation of composition of the Confederation occurred. On the other hand, if calculated over the period 2000–2018, an increase of 20% in energy consumption for CIS is observed. The highest increase is observed for developing countries, with India, China, Middle East and Africa leading the world growth of energy consumption

Most of the total energy (81+%) comes from fossil-C-based sources (coal, lignite, oil, gas), which are converted into other forms of energy such as thermal, electrical, mechanical, etc. with a quite low efficiency in the range 27–50% and an average of ca. 30–33%. Major users are the production of electric energy, industries and transport. The remaining part of the original chemical energy of fossil-C is lost as heat, often at high temperature, that ends with a direct heating of the atmosphere and our Planet.

1.2 The Fossil-C-Based Energy Frame

Carbon-based fuels have been used by mankind as source of heat and energy, in general, since the first anthropogenic fire (Fig. 1.1). Man-controlled fire has a life of ca. 1.5 My.

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Fig. 1.1

The appearance of Hominins and Homo and the first anthropogenic fire. Reproduced from Ref [2] (CC BY 4.0). Pan Tr. = Pan Troglodytes; Pan pa. = Pan Paniscus; LCA = Last Common Ancestors of Hominins and Pan

Controlled fire has permitted the development of a quite large number of applications during millennia (heating, cooking, metal forging, electricity generation, transportation, etc.). Slowly, man moved from wood to coal, natural gas, and finally oil, always using C-based fuels (Scheme 1.1).

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Scheme 1.1

The use of C-based fuels over the time

1.2.1 A Short History of Coal

Coal was discovered around 3490 bC by Chinese people who soon started to make a household use of it. Later on, also Greeks and Romans started to use coal for diverse applications. Curiously, its brightness has suggested the use in jewellery and pieces of coal were used as pendants in necklaces or cufflinks by Aztecs, the earliest use of coal in Americas.

../images/490402_1_En_1_Chapter/490402_1_En_1_Figa_HTML.png

Still today, coal is used for making personal ornaments. Romans were the first to discover and extract coal in Britain, where already during the first two centuries after Christ coal was largely employed for many uses, including forging metals. The blooming of the Industrial age was possible thanks to coal. At the beginning of 1800, the countries today known as UK and USA were the largest producers and marketers of coal with 260 and 350 Mt/year, respectively. Since then, coal has been extracted all over the world where it is distributed with different abundance among countries. Australia, North America, Asia, Europe, and Africa are rich of coal that for decades has been the main source of energy.

W1.1 Average dry atmosphere composition and its pollution

Dry atmosphere, the gaseous mass that surrounds our Planet Earth, is composed of 78.08% N2, 20.94% O2, 0.93% Ar, 0.04% CO2, 0.00005% He, and other trace gases. Figures given above represent an average composition, which slightly varies with the height over the Earth surface: heavier gases (CO2, Ar, O2) are more abundant close to the surface, lighter (He) in the higher layers. Water vapor can be present in various amounts (humidity), depending on the climatic conditions. Emissions by fossil-C combustion cause accumulation in the atmosphere of pollutants that may cause damages to goods and humans. For example, the emission of S or N oxides (SOx, NOy) causes the formation of acid species which can fall down with rain (acid rain) and cause serious damages to humans, vegetation and even buildings.

Some apparently inert species can be converted by sunlight in the atmosphere and generate dangerous pollutants. Other gaseous species, like chlorofluorocarbons (CFCs) (vide infra), can pass the troposphere unaltered (Chap. 2) and reach the stratosphere where they are converted by UV solar radiations into species which destroy ozone and cause the known ozone hole. Particulate of various dimensions can be suspended in the atmosphere and reach a variety of targets. Inspiration of very fine particulate (PM2.5 and PM5, dimensions of 2.5 and 5 micrometers) is very dangerous as it can reach deep parts of the respiratory apparatus and cause cancer.

The actual worldwide production of coal is summarized in Table 1.2: it amounts to ca. 7 732 Mt/y, including lignite. China is the largest producer and user of coal, facing quite heavy environmental problems. As a matter of fact, coal is a strong emitter of pollutants when burned, because it contains sulfur that generates SOx and metals (even some toxic metals) that accumulate in ashes, in general, as oxides. During the combustion, a fine particulate is emitted that causes deep atmosphere alteration (W1.1). During the great coal age (1800s–1900s), when coal was largely used for heating civil buildings, smog was wrapping large cities (famous is the London gray-greenish atmosphere, after which a color was named, the London gray). After 1970s, the growth of the environmental consciousness pushed toward the cleaning of coal used in heating of civil buildings in cities and in industrial processes. Deep pre-treatment of coal (desulfurization) and abatement of particulate were implemented over a large scale, or even coal was substituted with cleaner fuels (natural gas) so that the situation is today much improved, even if largest cities, located in not well-aerated areas, have still to face critical situations. Technology innovation has made that the direct burning of coal is even avoided and instead it is converted into other forms of cleaner fuels, mostly through its conversion ("reforming process") into syngas—a mixture of CO and H2—which is converted through the catalytic Fischer–Tropsch (FT) process into gaseous, liquid, and solid products (see Chap. 2). South Africa and Malaysia make most of their gasoline through FT processes. The application of technologies such as Water–Gas Shift (WGS) to reforming allows to convert coal and water into H2 and CO2 (Eq. 1.1a–1.1b) that are separated and H2 can then be used in a clean combustion with oxygen affording water as combustion product. (Eq. 1.2). If such reaction takes place in a cell (fuel cell), electricity is produced.

Table 1.2

Worldwide production of coal

$$ {\text{C + H}}_{ 2} {\text{O}} \to {\text{CO + H}}_{ 2} \to \left( {\text{syngas}} \right) $$

(1.1a)

$$ {\text{CO }} + {\mathbf{H}}_{{\mathbf{2}}} {\mathbf{O}} \to CO_{2} + H_{2} \left( {\text{WGS}} \right) $$

(1.1b)

$$ H_{2} + { 1}/ 2 {\text{O}}_{ 2} \to {\text{H}}_{ 2} {\text{O }} + {\varvec{Energy}} $$

(1.2)

This approach is at the basis of the innovative technology known as Integrated Gasification Combined Cycle (IGCC) that allows decarbonization of fuels with CO2 capture prior to combustion for making electric energy (see Chap. 2).

1.2.2 Natural Gas: Its Discovery, Early and Actual Uses

Natural Gas (NG) is known since 1000 bC and was discovered in China. Spontaneous emissions were used as flames in front of or inside temples by antic Greeks. Such emissions were also known as "eternal fires," mostly used as house ornament. Chinese people first tried to transport NG using bamboo pipes. In 1800, NG was transported using cast iron pipelines and largely used for lightening houses and streets (UK, since 1785, and USA were pioneer in such application). The discovery and exploitation of oil pushed NG to a second level of importance because of the easier transportation of oil and its higher energy density. Today, NG is coming back to massive use because it emits less CO2 than oil and coal for the same energy generated. In fact, for producing one kWh of electric energy, ca. 1 kg of CO2 is produced burning coal, while only 0.5 kgCO2 are emitted using NG, with oil sitting in the middle. NG is considered a clean fuel for use in houses (heating, cooking), transport (cars), industry (process powering), and electricity production. Table 1.3 gives the worldwide production of NG.

Table 1.3

Worldwide yearly production of natural gas as billion cubic meters (bcm)

NG, which is made mainly of methane, is also used in the chemical industry as starting material for producing chemicals (see Chap. 2) through its conversion into syngas (methane reforming). The recent economic implementation of the technology of "shale fracking" (hydraulic fracturing of shale clay rocks that contain gas formed upon decomposition of organic materials) has opened a new market that is already exploited at an interesting level in USA.

1.2.3 Oil and Its Superior Properties

The discovery of oil dates back to 650 bC in China where first attempts to transport by pipelines (made of bamboo) were also made. It had a spot utilization until 1859, when it was discovered and drilled in Pennsylvania, USA. With the discovery of the Texas-USA wells in 1901, the large-scale commercialization of oil started. Today, oil is drilled all over the world not only on Earth surface, but also in seas and oceans, reaching deepness (7 000+ m) not imagined 40 years ago. Oil is the main source of fuels and chemicals today. On oil refining and conversion is based the largest chemical industrial sector: petrochemistry. The total production of oil today is reported in Table 1.4.

Table 1.4

Worldwide production of oil in Mt/y 2018

Oil is the most concentrated form of solar energy. Table 1.5 reports the energy density of several vectors. Long-chain liquid hydrocarbons distilled from oil are by far the most efficient energy carrier, better than coal, NG, methanol and much better than H2 and batteries. This property makes oil the most suited source of fuels for cars and several other applications. Oil is easy to ship everywhere and can be easily stored in tanks without problems. If it is carefully handled and used, it does not create any problem to the environment and health. For this reason, oil finds ubiquitous use and is difficult to substitute in transport and other applications.

Table 1.5

Energy density of various vectors

1.3 The Fossil-C Availability

Fossil-C is, in principle, renewable, but, unfortunately, it cannot be regenerated at the rate we use it: its availability is got to inexorably decrease with time. This is due to the difference between the rate of combustion of biomass and that of biomass generation: the former is some 1 000–10 000 times faster than the latter. In fact, the rate of production of CO2 by combustion of carbon-based materials (6 − 15 gCO2 m−2 s−1 for several kinds of wood [3]) is much faster than the fixation of CO2 by photosynthesis (the best values are observed in microalgae [4], more efficient fixing agents than terrestrial plants, in the range 0.1−1.7 gCO2 L−1day−1 or 0.00057 − 0.0098 gCO2 m−2s−1). Additionally, the increasing population (our planet population is 7 Bpersons today and is expected to grow to 10 Bpersons by 2030), the ethic question of assuring a decent quality of life to 1.1 Bpeople (UNICEF 2017) who live in poverty (with 750 Mpeople living in extreme poverty), and the general wish of improving the worldwide average standard of life demand more energy.

In several areas, deforestation is pervasive (land is used as arable soil or for setting new production sites or inhabitations): the agents able to fix CO2 (trees) are decreasing in number while the emitters (humans) are increasing with time, reinforcing the CO2 accumulation in the atmosphere.

However, our society is squeezed between two walls: from one side the increasing need of energy for satisfying wishes of a high standard of life of an ever-increasing number of persons and from the other the impossibility of satisfying such necessity in the usual way (use of fossil carbon), because of the scarce availability for the future generations and the putative negative effects of the emission of CO2 on climate.

For how long can we rely on fossil carbon, then? Table 1.6 gives an estimate of the reserves of fossil carbon per geographic area. The distribution is important because political factors may affect the general usability of resources.

Table 1.6

Estimated world fossil-C reserves (Gtoe)

The total amount of extracted fossil-C in 2018 was categorized below:

Oil: 4 472 Mtoil,

Coal and lignite: 7 732 Mtcoal and lignite, and

Natural gas: 3 955 Bm³of natural gas.

Not all such carbon was used. For example, oil was used at a rate of 4 300 Mt in 2018.

When burned, fossil fuels and biomass all produce CO2 and the total amount of emitted CO2 by fossil fuels use was 32 000 MtCO2 in 2018. Fossil-C is used at a large extent for producing electric energy. Different C-fuels have different specific capacities of producing electricity and cause different specific emissions. Table 1.7 shows how differently various C-sources behave with respect to the production of a given amount of electric energy (1 kWh, Column 2, or 1 GJ, Column 3) and the relevant CO2 emission: if compared to natural gas (last entry in Table 1.7), oil (Entry 8) emits 40% more CO2, hard coal (Entry 8) 70%, and lignite (Entry 3) 80%. Peat and wood are still worst. The use of biomass as source of energy is becoming quite appealing with respect to fossil-C because biomass is formed from atmospheric CO2 and, in principle, would produce energy at quasi-zero CO2 emission. Indeed, the zero-emission option is not feasible because even using spontaneous natural biomass, energy is used in the collection-transport-processing of biomass that must be taken into account.

Table 1.7

CO2 emission in the combustion of various C-based fuels (natural or man-made) for producing 1kWh (1 GJ, Column 3) of energy

*) Commercial quality pellets are considered as a widespread thermal energy source. See Chap. 4

Different biomasses have different energy contents, much lower than fossil-C, and emit larger quantity of CO2: humanity today and in future cannot leave on biomass as the only source of energy (See Chap. 4).

Table 1.8 reports the capacity of biomass power plants in selected countries and worldwide in 2018 (in gigawatts) [5]. As capacity is intended the total installed power, even if not really used.

Table 1.8

Capacity of biomass power plants in selected countries, GW

Currently, biomass covers approximately 10% of the global energy supply, of which two-thirds are used in developing countries for cooking and heating. In 2009, about 13% of biomass use was consumed for heat and power generation, while the industrial sector consumed 15% and transportation 4% [6].

Another point of consideration is that direct burning of biomass is not a clean process: it has a strong environmental impact in terms of emitted particulate, unburned materials, N-containing organic pollutants derived from wood-endogenous-N, dioxins, etc. For the large-scale combustion of biomass, especially in large cities, clean technologies are needed that prevent atmospheric pollution.

The benefit is in the fact that biomass is produced from atmospheric CO2: the International Panel on Climate Change (IPCC) estimates that the modern biomass usage has a large carbon mitigation potential. The mitigation potential for electricity generation from biomass will reach 1 220 MtCO2eq for the year 2030; a substantial fraction of it at costs lower than 19.5 US$2005/tCO2.

The massive use of pellets for heat generation in urban areas is causing the formation of heavy smog. In order to reduce the environmental burden, it is necessary to process biomass into clean fuels before using it: this will rise issues about its economic and energetic cost. Even if the use of renewable sources (biomass) and perennial energies (solar, wind, geo, hydro-SWGH power) will be expanded, it is unlike that perennial and renewable sources will cover the need of energy of humanity. The use of fossil-C use will be progressively reduced up to minimize it, but will not reach zero. Most likely, fossil-C will still be necessary for feeding high-density and high-intensity uses, such as heavy electric terrestrial transport, naval transport and aeronautics, and as raw material for the chemical industry (that cannot be decarbonized), while perennial and renewable sources will likely be used for low-density and low-intensity uses (domestic uses and some kind of light transport). However, the combustion of fossil-C is causing the emission into the atmosphere of large amounts of CO2 which accumulates and rises serious concerns about its putative impact on climate change. Therefore, the reduction of CO2 emission is a must for our generation.

This urgency is aggravated by the fact that natural resources are not infinite: even if the availability reported in Table 1.6 can somehow be expanded by discovering new oil or gas fields or coal mines and by developing technologies that will allow the exploitation of fields today not reached, it is a matter of ethics to save resources for next generations, limiting consumption today: they will not last forever. At the actual rate of consumption, we have enough fossil-C for only 70 years. Our dilemma is that our society demands more energy, while we should use less C-based primary sources. How to match, thus, the request of more energy and the need to reduce the use of fossil-C that provides 81+% of the total energy used today? The most intuitive answer is: increasing the efficiency in the production and use of energy and exploiting alternative non-C-based energy sources. This is all? Any other innovative solution? Yes. A revolutionary approach to problem-solving based on "Carbon Recycling-CR" is growing, based on technology innovation, system integration, and coupling chemistry–catalysis–biotechnology. Carbon recycling merges the intensity typical of man-made (or industrial) processes with the Nature-inspired "cooperative-systemic-cyclic concepts. The aim is a Man-made C-cycle" that may enhance the rate of CO2 conversion with respect to natural processes, and its integration with the natural C-cycle for producing goods and fuels: recovery and reuse of carbon is a new paradigm in the CO2 problem. It is our firm belief that such a complex problem, namely, the CO2 emission reduction, cannot be solved by a single option exploitation, and requires instead an integrated solution and C-recycling is a strong part of it.

1.4 Recovery and Reuse of Goods

Recycling of goods is a practice applied to several materials since very long time: it is time now that we apply the same concept to carbon. Metals (aluminum, copper, iron, gold, silver, and many others) are recovered from industrial slags and/or used products and reused in order to save natural resources and, in some cases, prevent pollution and save energy. Also, municipal or industrial wastewater is treated, sanitized, and reused at large extent in some geographical areas. Glass is recovered at the end of life of bottles and other goods and reused. Paper is recovered and reused. It is becoming more and more imperative these days to recover and reuse plastics.

Now, it is time that we learn to efficiently recover and reuse carbon. Here is our future.

Table 1.9 gives an idea of the nature and percentage of goods that are recovered and recycled. It is worth to mention that recycling of a given good can be performed either in the same production cycle (primary recycling) or in a different process that produces goods of lower quality and use. For example, plastic used for food packaging once recovered and recycled most likely will not be used for producing the same quality plastics because of potential pollutants that are incorporated in it.

Table 1.9

Some hints in recycling of goods in anthropic activities

Unless food-level purity is matched, recovered plastics will be used in a lower level application: they will be suited, thus, for producing items not used in the food sector, such as materials for industrial applications or pipes for irrigation. Medical plastics are not reused as they can be carriers of infectious microorganisms and cells.

Reuse requires a lot of care, for avoiding that health of humans may be affected: this is true for all goods, including carbon. Recovered (from power plants or industry) CO2 can find use in several non-chemical applications (see Chap. 8), including additive to beverages, preservative of food, and modified packaging: only food-grade CO2 will be used in the three latter applications. Table 1.9 shows that carbon (in the form of coal, oil, gas, and biomass) is by far the most used good, but also the one that is less recycled (as %), as for now. The reasons why will be discussed in following chapters and how such situation is changing will be described.

References

1.

https://​yearbook.​enerdata.​net/​total-energy/​world-consumption-statistics.​html

2.

Gowlett JAJ (2015) The discovery of fire by humans: a long and convoluted process. Phil Trans R