Renewable energy and green energy are sometimes confused as the same thing, but, it’s important to identify that they are not.
You can have a renewable energy source that isn’t green, and vice versa.
We’ve made this guide very short, but we point out the important differences between the two – along with some examples.
Summary – Renewable Energy vs Green Energy
- Renewable energy is generally defined as energy that comes from a natural resource, and regenerates in a short period of time (and doesn’t deplete easily), or within a human lifetime (as opposed to fossil fuels for example that take thousands and millions of years to form). Renewable energy is not finite like fossil fuels
- Green energy doesn’t have one single definition, but it can also be described as clean, sustainable or eco friendly energy. A good way to define green energy might be an energy source that has a minimal impact on the environment and its resources over the lifecycle of the energy process, or specifically during operation and other stages of the energy process
- It’s easy to see how there can be natural energy sources that renew quickly, but when looking across their entire lifecycle, may require resources to make, may emit air pollution and emissions in use, and may have waste products after use
Examples Of Renewable Energy Sources
The short list is:
- Solar (PV – photovoltaic, and thermal)
- Wind (onshore, and offshore)
- Hydropower (run-of-river, storage, pumped-storage)
- Geothermal (steam, and water)
Examples Of Green/Clean/Sustainable/Eco Friendly Energy Sources
What is classified as a green energy source is more subjective.
But, in addition to renewable energy sources, nuclear may be seen as a green energy source as well – at least in operation (nuclear reactors have essentially no air pollution or greenhouse gas emissions while in operation). Having to mine uranium, and radioactive active waste as a by product though do take away from how green nuclear is as an energy source over it’s full lifecycle.
Fossil fuels such as coal, natural gas and oil are not seen as green or renewable energy sources. Coal especially is highly polluting and emits carbon dioxide. Natural gas tends to be the cleanest of the 3 fossil fuel energy sources.
An Example Of A Renewable Energy Source That Isn’t Always Green
Bioenergy and biofuel from biomass are a good examples.
Bioenergy comes in different forms, and is produced differently, as well as used for different things – so, not all bioenergy can be categorised under the same labels. This is especially true in the case of conventional vs modern bioenergy technology.
But, it usually comes from specially grown biomass crops, or from waste from various sectors.
In the case of crops grown for bioenergy or biofuels, it would be fair to say that these energy sources are not as green as other sources like wind and solar if there are issues like:
- Additional land clearing and deforestation to make land available for bioenergy crops
- Land degradation
- Inputs required to grow the crops like water, fertilizer and pesticides
- Biodiversity or monocropping issues from growing one type of biomass
- Issues to do with GE bio crops
- Pollution and emission issues from the growing of the crops and the refining of fuels or burning of organic matter to produce energy or fuels
- Lost energy and efficiency in converting crops into energy (biomass in general has been shown to be far less efficient than other energy sources in terms of energy conversion according to data on the efficiency of different energy sources)
Other resources on the questionable eco friendliness or green-ness of biomass, bioenergy and biofuels are:
An Example Of A Green Energy Source That Isn’t Renewable
Nuclear, and to a lesser extent bioenergy.
Nuclear is clean whilst in operation, but uranium isn’t a renewable resource yet. There is research being done of different types of reactors that would allow us to get more energy from the same amount of uranium, and also on how we can extract uranium from saltwater in a cost effective way at scale – and although this would make uranium incredibly abundant, neither method makes uranium technically renewable.
Bioenergy you could argue is renewable, but, it still takes far more time to grow crops or trees than it takes to instantaneously get energy from the sun or wind. You could also argue that resources required to produce bioenergy, even from waste products of other processes, could eventually become finite if critical resources like water start becoming scarce, or the environment starts to deplete and deteriorate to a critical extent.
What Energy Sources Are Renewable & Green?
Two energy sources that might best fit this description that are widely used today are solar PV energy, and wind energy.
Both use renewable sources of energy in the sun’s radiation, and the wind.
And, both have essentially no emissions or pollution whilst in use, and no waste product.
These sources aren’t without their cons though – as power density and variability can be just two of the drawbacks to solar and wind energy (they usually need a baseload backup energy source like some type of fossil fuel or nuclear).