In this blog post, we’ll examine the necessity and limitations of fossil fuels and explore how we can address sustainability and environmental issues.

Definition and Overview of Fossil Energy

The English word “energy” refers, in physics, to the ability to perform work. Furthermore, since an energy source is required to generate physical energy, the term “energy” is often combined with the name of the specific source—such as nuclear energy or hydroelectric energy—to denote that particular energy source. These energy sources are closely linked to the development of human civilization and play essential roles in our lives in various ways.
Fossil energy is one such energy source and is generally used to refer to fossil fuels. Fossil fuels are a form of energy among the various sources used by humans; they are energy resources formed from the remains of organisms that inhabited the Earth long ago. Types of fossil energy include coal, petroleum, natural gas, bituminous shale, tar sands, and oil sands. It is called “fossil energy” because it shares the same formation process as the fossils we commonly know.
Fossil fuels began to be converted into physical energy and used on a large scale with the spread of steam engines during the British Industrial Revolution. This period was not merely a time of mechanical and technological advancement but a revolutionary turning point that fundamentally transformed humanity’s way of life. Since then, as science has advanced, technologies have been developed not only for exploring, mining, and drilling for buried fossil fuels, but also for refining them from their natural state, transporting them to where they are needed, and maximizing efficiency when converting fuel into energy. Based on these technological advancements, fossil fuels currently account for the largest share of humanity’s energy sources.
Due to their high efficiency and reliability as an energy source, fossil fuels play an indispensable role in numerous industrial sectors. They are used for various purposes, such as power generation, transportation, and heating, and their economic importance is also significant. The U.S. Energy Information Administration estimates that the major energy resources are oil (36.0%), coal (27.4%), and natural gas (23.0%), and that fossil fuels account for 86.4% of global energy consumption. Furthermore, as the population grows, fossil fuel consumption is on an upward trend each year. Because fossil fuels account for such a massive share of human energy production, issues surrounding them affect every aspect of human life. Among fossil fuels, petroleum has a profound impact on the economic activities of ordinary consumers, and fluctuations in oil prices have become a key indicator of economic health.

The Formation Process and Characteristics of Coal

Coal is formed when ancient plants are buried underground and undergo metamorphism; however, there are two theories regarding the burial process. These are the non-depositional theory, which posits that plants were transported to a specific location by floods or other causes and then buried, and the in-situ depositional theory, which holds that plants were deposited and buried at the very site where they were produced. Both theories agree that it took a long time to form thick coal seams over a wide area, and that these seams were formed in locations such as sedimentary basins where the ground gradually subsided. It is believed that, as the ground subsequently subsided at a rapid rate, the coal seams were covered by soil and, after undergoing several cycles in which plants flourished anew on top of them, were eventually buried deep underground.
The plants that formed coal are believed to have been primarily terrestrial rather than aquatic, and in terms of age, about one-third of the world’s coal deposits date back to the Paleozoic Era (500 million to 200 million years ago), with most of the coal in Europe, North America, and Asia falling into this category. While coal has the advantage of being a relatively inexpensive energy source, it has the disadvantages of being difficult to mine and transport, and having a low calorific value when burned. Furthermore, the air pollutants generated during coal combustion can have serious impacts on the environment and human health.

The Formation Process and Characteristics of Petroleum

There are two theories regarding the origin of petroleum: the “abiogenic theory,” which posits that methane was formed through a reaction between underground iron carbides and water, and the “biogenic theory,” which suggests that it was formed through a process of thermal maturation after organic matter—biological organisms—was buried along with sediment. Currently, the biogenic theory has become the generally accepted scientific consensus. Therefore, the potential for petroleum formation depends on when and where vast quantities of organic matter were buried, as well as the extent of the thermal maturation process they underwent.
According to the biogenic theory, organic matter is buried underground and transformed into petroleum or coal; depending on the type of organic matter, it is classified as either petroleum or coal, and petroleum is further divided into crude oil and natural gas based on the type of organic matter, as well as underground pressure and temperature. Generally, in the sedimentary environments of the continental shelf, when phytoplankton and algae accumulate in large quantities and undergo maturation at temperatures of 60–130 degrees—which is lower than the metamorphic temperature of rock—petroleum is formed; at higher temperatures, gas is produced. Furthermore, in terrestrial sedimentary environments, when terrestrial plants are buried in large quantities and undergo maturation, coal is formed.
When organic matter is buried along with sediment, source rock—the source material for petroleum—is formed. Furthermore, the rock in which the resulting petroleum migrates and accumulates is called reservoir rock, and the rock that caps the reservoir from above, preventing the accumulated petroleum from migrating elsewhere, is called cap rock. For petroleum to exist, source rock is required; black shale, formed between the Upper Jurassic and Lower Cretaceous periods, accounts for 85% of the world’s source rock.
In 1970, Moody analyzed giant oil and gas fields containing more than 500 million barrels and reported that 48% of these giant fields were distributed in the Mesozoic Jurassic and Cretaceous periods, while 39% were found in Cenozoic Tertiary strata; he also noted that trap systems forming collection basins were most likely to be located on the continental shelf. A trap refers to geological conditions that accumulate oil or gas generated from underground source rocks. The advantages of oil include its liquid state, which makes transportation and handling from extraction to use simple and convenient; its high calorific value; and its ability to be processed for various applications in modern industry. On the other hand, its disadvantages include significant regional disparities in reserves among countries and its high price relative to coal due to its smaller volume.

Formation Process and Characteristics of Natural Gas

Natural gas undergoes a formation process similar to that of coal. While it is sometimes produced mixed with crude oil, it is mostly produced separately. The main component of natural gas is methane, and it is highly valued as an energy source because it produces almost no pollutants when burned. It is also noteworthy for its low price and the fact that, being lighter than air, it poses little risk in the event of a leak. Natural gas is widely used, particularly as city gas and industrial fuel, and demand is increasing as its reputation as a clean energy source spreads.
However, natural gas has the drawbacks of being difficult to detect and, due to its gaseous nature, being inconvenient to transport and handle. Effective utilization of natural gas requires advanced technology, which can result in additional costs.

The First Problem with Fossil Fuel Use: Limited Reserves

As evident from the formation process of fossil fuels, their formation cycle spans millions of years, which is why they are classified as non-renewable resources. Therefore, if we recklessly consume the limited supply of fossil fuels generated within the finite space of Earth without any planning, these resources will eventually be depleted, and humanity will no longer be able to produce energy. This concern is one of the reasons that underscores the need for long-term management of energy resources and sustainable development.

The second problem associated with the use of fossil energy: environmental pollution

The conversion of fossil energy into usable energy generates significant amounts of carbon dioxide, which Earth’s plants are unable to absorb entirely. Consequently, the amount of carbon dioxide in the atmosphere will continue to rise, and many scientists argue that this increase in carbon dioxide levels is causing global warming. Global warming can lead not only to extreme weather events but also to various other unpredictable problems. Furthermore, nitrogen oxides and sulfur oxides emitted during the combustion of fossil fuels dissolve in rainwater, forming acid rain that increases soil acidity and causes environmental issues such as the erosion of historical sites.

The Future Direction of Energy and the Need to Replace Fossil Fuels

Modern society is focusing on developing various energy sources to replace fossil fuels. Renewable energy sources such as solar, wind, and geothermal power are emerging as alternatives capable of overcoming the limitations of fossil fuels. These renewable energy sources enable a sustainable energy supply while minimizing negative environmental impacts, and governments and companies around the world are striving to develop the necessary technologies and expand the infrastructure to support them.
In particular, reducing fossil fuel consumption and transitioning to clean energy are essential for maximizing energy efficiency and strengthening environmental protection. This goes beyond a simple energy transition; it is a necessary choice to protect the Earth’s environment and leave a healthy planet for future generations. Discussions on energy transition and sustainability have now become a global priority, and as these discussions gradually take shape, the future energy paradigm is shifting.