Nonrenewable Energy Sources

Geological Reserves of Nonrenewable Sources Are Finite

Non-renewable energy sources come from limited stocks that form much more slowly than people consume them.

Let $r_{\mathrm{use}}$ be the human use rate and $r_{\mathrm{form}}$ the natural formation rate:

r_{\mathrm{use}}\gg r_{\mathrm{form}}

The symbol $\gg$ means "much greater than". To judge a fuel supply, check how much is available and how quickly it is being used.

Fossil Fuels and Nuclear Fuel

The two main groups of non-renewable sources are fossil fuels and nuclear fuel. Fossil fuels formed from ancient living remains that were buried, then changed by pressure and heat over $\text{millions of years}$ .

Nuclear fuel is used in fission, a process in which a heavy atomic nucleus splits and releases energy. Nuclear power plants do not burn carbon at the plant. They use uranium as fuel.

Source	Initial energy	Origin and use
Coal	Chemical energy	Coal forms from ancient plant remains that changed into carbon-rich solid fuel.
Petroleum	Chemical energy	Petroleum is a liquid hydrocarbon mixture refined into fuels such as gasoline and diesel.
Natural gas	Chemical energy	Natural gas consists mainly of methane, which can be burned to produce heat.
Uranium	Nuclear energy	Uranium comes from minerals mined for nuclear reactor fuel.

The term "non-renewable" includes both fossil fuels and nuclear fuel. Coal, petroleum, and natural gas are burned, while uranium releases energy through nuclear fission.

Heat Is a Shared Conversion Step

Many power plants using non-renewable sources produce electricity through heat. The plants differ in how they produce that heat.

In fossil fuels, chemical energy becomes heat through combustion. In uranium, nuclear energy becomes heat through nuclear fission. After heat is available, many power plants use steam to spin a turbine and generator.

Fossil fuels and uranium both reach the same final energy form, electricity. The early path is different, but each source still needs a conversion device before its initial energy becomes useful energy.

Different Roles on the Power Grid

Power plants do not all supply electricity in the same way. Nuclear plants usually run continuously at a steady output. Natural-gas combined-cycle plants can raise or lower their output as demand changes. When demand reaches a peak, combustion turbines fueled by natural gas or petroleum can add electricity for a few hours.

In the U.S. electricity system, these are called base-load, intermediate-load, and peak-load roles.

This operating pattern determines whether a plant supplies steady base load, follows changes in demand, or serves a short peak. Evaluating its energy source also requires checking the fuel stock, emissions, waste, and the effects of mining or drilling.

Risks Across the Full Energy Chain

The effects of a non-renewable source begin before the power plant and continue after energy production.

Risk	What to check
Limited stock	Check whether use depends on reserves that become harder to obtain.
Combustion emissions	Check exhaust gases such as carbon dioxide and air pollutants.
Extraction impact	Check how mining and drilling affect water, soil, and nearby habitats.
Nuclear waste	Check radioactive material storage and reactor safety standards.

Carbon dioxide is written as $\text{CO}_2$ . Natural gas consists mainly of methane, written as $\text{CH}_4$ . Burning fossil fuels releases carbon dioxide.

Using a non-renewable source draws down a stock that returns very slowly. Whether that choice is appropriate depends on its purpose, effects, and available alternatives.

Assess each source by its stock, conversion path, useful energy, waste, and effects on communities and ecosystems.