Why we rely on fossil fuels?

Our society has been relying on fossil fuels such as oil, natural gas, and coal. However, the concept of carbon neutrality has now been set as a global target, necessitating citizens, policy-makers to consider decarbonization. Among fossil fuels, coal is considered the most carbon-intensive that releases carbon dioxide the most, while natural gas is included in EU taxonomy.^[1] Why have we relied so much on fossil fuels?

The simple answer would be "because fossil fuels contains so much of energy". This post summarizes the benefit of fossil fuels with focus plased on energy.

This figure below (in Japanese, to be translated into English) illustrates the flow of fossil fuel usage. Upper in the figure, the higher in energy.

エネルギー：Energy
化石資源：fossil fuels
石油化学製品：chemicals、高付加価値製品：value-added product
焼却処理：combustion
二酸化炭素：carbon dioxide
電力や燃料：electricity, fuels

Fossil fuel as a source of energy (anticlockwise direction in the figure)

Among the usage of fossil fuel as an energy source, the most representative is the generation of electric power. The electric power generations starts with combustion of fossil fuel to generate heat, which evaporates the water into steam. The change in phase from liquid to gas accompanies a significant increase in its volume, which is used to turn the turbine. "combustion of fossil fuel" corresponds to the exothermic reaction described below:
fossil fuels + O₂ --> CO₂ + H₂O ...(1)
In other words, the energy stored in fossil fuel is rearranged into energitically poor CO₂ and H₂O, by which we extract the energy of fossil fuels.

Fossil fuel as a source of chemical production (clockwise direction in the figure)

Carbon, hydrogen, and oxygen constitue the most of chemicals that we use in our daily life, including plastics and medicines. The chemicals are produced by making use of hydrocarbon frameworks that the fossil fuels contain (for instance, C-C and C=O boinding, benzine rings). Because the bonding corresponds to energy (to be described in another upcoming post), and fossil fuels contain a lot of energy, such an arrangement of bonding is possible. After the use, the chemicals can be burnt and broken into CO₂, for instance.

Making good use of fossil fuels allowed us to develop the current society. However, it has accompanied emission of sigificant amount of CO₂ into atmosphere. From the view-point of energy, it would be a key to making good use of CO2 located at the bottom of energy landscape for realization of carbon-neutrality.

References

1. European Commission, "EU Taxonomy: Commission begins expert consultations on Complementary Delegated Act covering certain nuclear and gas activities", https://ec.europa.eu/commission/presscorner/detail/en/ip_22_2 (accessed on 2022/02/02)