This blog post examines how fossil energy, which propelled human civilization’s advancement, has led to environmental problems, highlighting its merits and demerits alongside future challenges.
The use of fire is an indispensable element in humanity’s establishment of civilized society. The background enabling the transition from the Stone Age to the use of bronze and iron tools involved smelting metals using fire. By harnessing the energy of fire, humanity overcame various constraints and achieved growth. In the past, wood was used to smelt metals and obtain the thermal energy necessary for daily life. For centuries, the utilization of thermal energy saw only gradual growth. Then, in the 18th century, the invention of the steam engine and the use of coal enabled a revolutionary leap in energy utilization. Improvements in steam engine design increased efficiency, and the use of coal—possessing vastly greater energy compared to wood—made it possible to convert enormous thermal energy into kinetic energy for use. The rapid growth of humanity in the 19th century was enabled by coal, which allowed the utilization of vastly greater energy compared to the past. Subsequently, in the 20th century, petroleum and natural gas drove the rapid advancement of civilization. Human prosperity was built upon the use of fossil energy. Now, let us explore fossil energy, which has driven the rapid development of human civilization.
Fossil energy, or fossil fuels, refers to natural resources buried underground, such as coal, petroleum, and natural gas. All fossil energy sources are essentially aggregates of organic matter containing large amounts of carbon. They are energy sources formed when the remains of ancient plants and animals were buried by tectonic forces, subjected to the Earth’s internal heat, and underwent long periods of displacement and transformation. Due to the advantage of yielding immense energy through combustion, their usage has surged dramatically since the Industrial Revolution. Fossil energy remains the most crucial energy source underpinning modern human civilization.
Coal is a fossil energy source formed from plant matter and primarily composed of carbon. When massive trees become buried and submerged in soil, more soil is deposited on top. After plant communities form, this process repeats. As the accumulated plant material underground is subjected to high temperatures and pressures, its hydrogen and oxygen content decreases while its carbon content increases. This phenomenon is called carbonification. Coal is classified according to its degree of carbonization, divided into peat, lignite, bituminous coal, and anthracite. The degree of carbonization increases from peat to anthracite, exhibiting higher carbon content and lower hydrogen and oxygen content. Because coal formed through the metamorphosis of plants, it is often thought of as a simple aggregate of organic matter. However, it actually exhibits a more complex composition. Coal is a complex mixture of microscopic organic components called macerals, identifiable under a microscope; ash, soil components mixed in since deposition; and volatile components, sulfur, and moisture, which are crucial alongside carbon content for coal combustion. Consequently, a series of processing steps, known as coal preparation, is necessary before coal can be used. The coal we utilize is the coal that has undergone this preparation process.
When considering the use of coal, one might think coal is synonymous with briquettes, recalling the volunteer briquette distribution scenes often seen in winter news reports. While briquettes are indeed a type of coal, they represent a rather low-grade variety. As can be inferred from the appearance of briquettes used as heating fuel, coal is an excellent energy source. Coal with high carbon content and a high volatile matter content, which provides good calorific value, is primarily bituminous coal or anthracite. This type of coal is used as an energy source in thermal power plants. Coal is used as the heat source to heat the boilers for power generation. This thermal energy is used to produce steam, which turns turbines to ultimately generate electrical energy. While the high efficiency of nuclear power plants and the promise of renewable energy might lead one to underestimate the role of coal-fired power plants, considering that coal still accounts for over 40% of domestic energy generation today, its importance is clear. Another major consumer of coal is the steel mill. At the boundary between bituminous and anthracite coal, certain types with unique properties exist; these are called coking coal and are used in steel mills to reduce iron ore and produce iron. Thus, coal is a particularly vital material in industry. Although it has been largely replaced as a transportation fuel since the advent of petroleum, it remains widely used as an industrial energy source.
Unlike coal, which is a solid composed of carbon, petroleum is a liquid hydrocarbon mixture. It is primarily formed when animal organic matter is deposited and then decomposed and altered by high temperatures and pressures within geological strata, or transformed into petroleum through microbial activity. This petroleum contains approximately 84–87% carbon and 11–14% hydrogen, along with small amounts of sulfur, nitrogen, oxygen, and other elements.
Another difference between petroleum and coal is that petroleum exhibits regional distribution. The majority of reserves are held by the United States, South America, the Middle East, Russia, and other regions. This regional distribution is linked to the principles of petroleum formation. Because petroleum is liquid, it cannot remain stationary in the terrain where it was formed. Instead, it migrates and accumulates in areas where it can pool, forming oil fields. While it is primarily found in sandstone layers—porous rocks suitable for petroleum infiltration—this is not true for all sandstone formations. Petroleum is mainly discovered in topographies structurally designed to trap it. One example is strata where geological structures like folds form, and overlying cap rocks exist that prevent further migration of the oil. Therefore, exploration targets such topography, and when an economically viable oil field is discovered, facilities are installed to begin production. An oil field does not simply contain liquid crude oil like water in a vessel. Rather, crude oil is trapped within the empty spaces, or pores, within the rock, much like water saturated within a sponge. When a metal pipe is installed through drilling between these rocks, the pressure in the fractured area is low. Consequently, the crude oil, which existed under high pressure, naturally rises through the low-pressure pipe. Traditionally, oil has been produced through such wells. However, due to pressure decline in the reservoir caused by continuous production and the need to ensure economic viability, new technologies like hydraulic fracturing are being introduced.
The produced crude oil is a mixture of various hydrocarbons and other compounds. Therefore, a process is necessary to remove impurities and separate the components by type. Refining utilizes the differences in volatility among the components within the crude oil. Separation proceeds from the lowest boiling point components, starting with gasoline, followed by diesel fuel, heavy oil, liquid paraffin, petroleum jelly, and finally asphalt remaining above 400 degrees Celsius. Gasoline is commonly used as fuel for passenger vehicles with gasoline engines or as a raw material in the chemical industry, known as naphtha. Diesel fuel and heavy oil are used as fuel for internal combustion engines like diesel engines or boilers. Asphalt, as commonly known, is extensively used in road paving. Recently, processes to decompose high-molecular-weight hydrocarbons and convert them into gasoline—a product with high demand and added value—are being researched and utilized.
Natural gas refers to a combustible gas primarily composed of gaseous hydrocarbons, especially methane. Since it is stored underground, it is produced using drilling wells, similar to petroleum. Natural gas is classified based on its production context: oil field gas, gas field gas, and coalbed methane. Oil field gas shares the same origin as petroleum; it exists alongside crude oil and is extracted during oil field development. Gas field gas is gas that has separated from oil fields, migrated, and accumulated independently within specific geological structures. Coalbed methane is gas trapped within coal seams that is released during coal mining.
Compared to liquid petroleum, natural gas was slower to be utilized as a fossil fuel due to challenges in handling and application. Refined natural gas has excellent value as a fuel. During the liquefaction process, impurities like dust, sulfur, and nitrogen are removed, resulting in minimal pollutant emissions during combustion, making it a viable clean energy source. It is used not only as fuel but also as a crucial feedstock in the chemical industry. Natural gas can be classified into liquefied natural gas (LNG), which is refined from standard gaseous natural gas and liquefied by compressing it approximately 600 times; compressed natural gas (CNG), which is compressed 200 to 250 times and stored in pressurized containers; and pipe natural gas (PNG), which is supplied via pipelines.
We have examined the fossil fuels we primarily use: coal, oil, and natural gas. Fossil fuels power cars and trains, making the use of appliances like computers and mobile phones a given. They are the foundation of the convenient lives we enjoy compared to past generations, and they continue to drive the world at this very moment. We cannot imagine abandoning automobiles and reverting to burning wood for fire. The brilliant civilization of modern humanity was made possible through the use of fossil energy.
However, this prosperity is not unconditionally positive. The indiscriminate use of fossil fuels for human convenience and profit has led to reckless development and worsening environmental pollution. Examples include uncontrolled development for resource extraction, global warming caused by massive carbon dioxide emissions, ozone layer depletion from nitrogen oxides, and acid rain and smog from sulfur oxides. Efforts are made to mitigate environmental pollution, such as removing sulfur through desulfurization equipment, eliminating nitrogen oxides via catalytic reactions, and using component conversion to remove toxic substances. However, these measures only delay greater damage; they are not complete solutions.
Alongside environmental pollution, fossil fuels demonstrate a serious risk of depletion due to their non-renewable nature, formed over millions of years. In fact, depletion is already occurring. Yet, the unfortunate reality is that alternative energies like nuclear power and renewables cannot yet fully replace fossil fuels. While it’s impossible to immediately eliminate all fossil fuels for the sake of the future, a new approach to fossil energy is necessary from the perspective of sustainable development. The fossil fuels that drove the evolution of human civilization will face new challenges in the 21st century.
