There are four main types of non-renewable resources: oil, gas, coal and nuclear. Oil, gas and coal are collectively referred to as fossil fuels. Fossil fuels are formed on Earth over millions of years by dead plants and animals – hence the name "fossil" fuels. They exist in layers of rock and sediment underground. Pressure and heat work together to convert plant and animal remains into crude oil (also known as oil), coal, and natural gas.
Plants and animals that became fossil fuels lived during the Carboniferous period, some 300 to 360 million years ago. The energy in plant and animal remains originally came from the sun; through photosynthesis, solar energy is stored in plant tissues, which animals then consume to replenish their own bodies. When fossil fuels burn, this captured energy is released.
Crude oil is a liquid fuel Fossil fuel, which is mainly used to produce gasoline and diesel fuel for vehicles, as well as for the manufacture of plastics. It is found in rocks below the Earth's surface and pumped out through wells.
Natural gas is widely used in cooking and home heating. It is mainly composed of methane and is found near petroleum deposits below the Earth's surface. Natural gas can be pumped out by the same well used to extract crude oil.
Coal is a solid fossil fuel used to heat and generate electricity in homes. It exists in fossil swamps buried under layers of sediment. Since coal is solid, it cannot be extracted like crude oil or natural gas; it must be dug out of the ground.
Nuclear energy comes from radioactive elements, mainly uranium, extracted from mined ores and then refined into fuel.
Unfortunately, human society is temporarily dependent on non-renewable resources as its main source of energy. About 80% of the world's total energy use each year comes from fossil fuels. We rely on fossil fuels because they are energy-rich and have relatively low processing costs. But a major problem with fossil fuels is that, in addition to limited supply, burning them releases carbon dioxide into the atmosphere. Rising levels of endothermic carbon dioxide in the atmosphere are the main cause of global warming.
Alternative energy sources, such as wind and solar, are possible solutions to the depletion of non-renewable resources. Both clean energy sources can be supplied indefinitely.