How Do Renewable and Low-Carbon Energy Differ?

• Group asking: does nature replenish the source
• Group asking: little carbon emitted when power is made
• Nuclear power: in the low-carbon group but outside the renewable group

What you will learn

• Tell renewable sources from nonrenewable ones.
• Say by which standard energy is called low-carbon.
• Explain why nuclear power pulls the two ideas apart.

Before you start

You only need to know that electricity is made from many kinds of sources. No specialist knowledge is needed.

What is renewable energy?

It is energy from sources that nature replenishes. A page from the U.S. Energy Information Administration (EIA) says renewable energy comes from sources that are naturally replenishing but flow-limited. They are virtually inexhaustible but limited by availability: another EIA page gives the example that solar energy is available only when the sun shines.

The opposite group is nonrenewable sources. According to EIA, they are called that because their supplies are limited to what we can mine or extract from the earth. Coal, natural gas and petroleum formed from the remains of ancient organisms, which is why they are also called fossil fuels.

• A tank refilled continuously: a renewable source
• A tank that only drains and is not refilled: a nonrenewable source

What is low-carbon energy?

It is a label about emissions when power is made, not about whether the source is replenished. An article from the U.S. Department of Energy describes nuclear power as a source of low-carbon electricity. Heat from fission makes steam that spins a turbine. EIA's nuclear power and environment page distinguishes the boundaries: reactors do not emit carbon dioxide while operating, but uranium mining, fuel production and plant construction use energy and have associated emissions. Low-carbon does not mean every stage is emission-free.

On the renewable side, EIA says renewable energy can play an important role in reducing greenhouse gas emissions, and can help reduce fossil fuel use, the largest source of U.S. carbon dioxide emissions. These sources do not compare the carbon of each renewable source, so the article gives no figures.

• Fossil-fuel plant chimney with red smoke
• Cooling tower of a nuclear plant, steam only

Why do the two ideas not coincide?

Because they ask two different things. Renewable asks: does nature replenish the source? Low-carbon asks: what is emitted when power is made?

Nuclear power shows the gap. EIA treats uranium as a nonrenewable source even though it is a common metal found in rocks worldwide, and all nuclear power plants use nuclear fission. The Department of Energy article, meanwhile, places nuclear power among low-carbon electricity. A source can be nonrenewable and still low-carbon.

• Fossil fuels: nonrenewable and emitting harmful byproducts
• Nuclear power: nonrenewable but low-carbon
• Empty cell: the article places no source here

Real-world example

Think of two ways to describe a car. One speaks of where the fuel comes from and whether it is replenished. The other speaks of the exhaust leaving the tailpipe. The two descriptions do not replace each other, and a car can be praised by one and criticised by the other.

Ask yourself: when someone calls a power source clean, are they talking about how it is replenished or about what it emits? Asking that helps you pick the right word.

Common misunderstandings

Low-carbon does not mean renewable. Nuclear power is described as a low-carbon electricity source, yet uranium is a nonrenewable source.

Renewable does not mean always available. Renewable sources are virtually inexhaustible but limited by availability, as solar energy is available only when the sun shines.

Nonrenewable does not mean rare. Uranium is a common metal found in rocks worldwide, yet it is still considered nonrenewable.

Frequently asked questions

Is nuclear power renewable or low-carbon?

According to the sources used, it is described as a low-carbon electricity source, while uranium is considered a nonrenewable source.

Does renewable energy help cut emissions?

EIA says renewable energy can play an important role in reducing greenhouse gas emissions and can help reduce fossil fuel use.

Which group do fossil fuels belong to?

The nonrenewable group, because their supply is limited to what we can mine or extract from the earth.

Summary

• Renewable is about whether nature replenishes the source.
• Low-carbon is about what is emitted when power is made.
• Nuclear power shows that a source can be nonrenewable and still low-carbon.