Green energy is the umbrella term that covers sustainable energy, renewable energy and low carbon energy.  Renewable energy sources are all sustainable, but they aren’t all low carbon. Here’s our guide to the jargon, so that you can tell your biomethane from your solar power.

Sustainable energy

Coal and oil are running out and there will come a point when the supplies disappear completely. They’re not sustainable sources for gas and electricity because we can’t create more fossil fuels. Instead, sustainable energy comes from energy sources that will still be available in the future, no matter how much of them we use up now. For example, biomethane is a gas that is created when dead plant or animal matter is anaerobically digested. It can be used in place of natural gas.

Whether nuclear power is renewable as well as sustainable has been a matter for debate. However, although the next wave of nuclear reactors will be fast neutron reactors, which are sustainable, the energy is not renewable.

Renewable energy

This is energy generated from sources that, well, are renewed: for example, wind, sun, water, tides. There may not be enough wind or sun to generate power every day, but there will be more wind and more sun. And, the amount of sunshine or tidal power that is used today has no effect on how much is available in the future.

Low carbon energy

Energy is classed as low carbon when it causes fewer carbon emissions than fossil fuels. That’s not just when it’s burnt but also takes into account what carbon emissions are generated in the production of the energy source. Renewable energy is usually also low carbon.

Carbon neutral energy

This is energy or fuel that either does not add to overall greenhouse gases in its production and use. Or, it does add slightly to greenhouse gases but that is balanced out by other carbon reduction activity. For example, your energy supply may also be carbon neutral because the carbon emissions created during its generation have been offset by planting trees.

Biomass boilers are a carbon neutral form of heating. They burn wood chips or pellets that are from sustainably farmed forests. When burnt, the wood only emits as much CO2 as the tree took in during its lifetime.

Table of energy sources

Energy/heat source Sustainable Renewable Low carbon
Coal gas NO NO NO
Nuclear YES NO YES
Biomethane YES NO YES
Geothermal YES YES YES
Hydropower YES YES YES
Tidal power YES YES YES
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