Cluster of wind turbines

As humans, we tend to bucket things into two categories: good or evil, hard or easy, rich or poor, stupid or smart. The same could be said for how people understand different energy sources: renewable energy or traditional energy, green power or brown power, clean energy or dirty energy. However, such perfect binaries don’t really exist, and the clean energy / “dirty” energy dichotomy is no exception to this.

When you think of clean energy, you typically think of renewable energy sources such as solar and wind — and you’d be right! You’d also get a checkmark if you wrote nuclear energy on a test. But you’d probably get half credit if you penciled in natural gas, depending on the person grading, since there’s obvious debate whether fossil fuels can truly be clean.

At Chariot Energy, we believe clean energy is synonymous with renewable energy — energy that doesn’t emit greenhouse gases or other pollutants. Still, others claim that nuclear energy, natural gas and even clean-burning coal are on the cleaner end of the spectrum. In this article, we delve into the different sources of clean energy — including nuclear and natural gas — and ultimately why we believe “clean” should be synonymous with “renewable.”

Clean Energy Sources

We will start by examining the 6 main sources of clean energy. Out of all energy resources, we consider green power (solar, wind, biomass and geothermal) as the cleanest form of energy. So, if we were looking at clean energy on a spectrum, these would be farthest from “dirty” or emissions-heavy energy.

We’ll then discuss natural gas, which some energy experts classify as a clean energy source (but we don’t think it is). Finally, we’ll talk about one particular energy source that we simply cannot bring ourselves to include. We share why that is later in the post.

1. Solar Energy

Our beautiful bread and butter, solar energy. We experience this amazing clean energy source through sunlight and heat, and we can utilize this energy to create electricity through technology like solar panels or concentrating solar power plants (reflective mirrors). We generate this electricity without any emissions or pollution, so it earns a checkmark.

Source: EPA

2. Wind Energy

Another clean energy source, wind energy is technically another form of solar energy since the sun is partly responsible for all weather patterns on Earth. However, for the sake of how electricity is produced by solar panels and wind turbines, they are considered two different forms of energy.

Like solar energy, power generated from wind turbines produces no air pollutants. So, it’s an easy check on our list of clean energy requirements.

3. Bioenergy

Scientists are working to create a super species of algae that can produce copious amounts of fat, which can be converted into biodiesel.

This is a really fun source of energy! Well, not fun, per se, but it’s nonetheless interesting. This form of renewable energy is created by living organisms such as algae, wood, crop residue. It can also come from food waste, landfills and fermented crops. The most common application is fuel for transportation and heating buildings.

It’s such a versatile form of energy because, while it can and does generate electricity, its most prevalent use lies in the creation of biofuels for transportation as a replacement for fossil fuels. And since we need fuel for everything from our cars to airplanes, bioenergy lowers the carbon impact on the environment. Check!

4. Geothermal Energy

Unlike water, solar and wind, geothermal energy isn’t derived from the sun. Instead, it is energy in the form of heat from the Earth itself. Most often, geothermal is used to heat and cool people’s homes.

To create geothermal electricity, the Earth’s heat energy is used to boil water to create steam. This steam then rotates turbines that generate energy. It’s similar to a coal-powered power plant, but it’s run on the Earth’s heat instead of burning fossil fuels.

Another checkmark!

5. Hydropower

A hydropower facility

Again, another source of energy technically powered by the sun, hydropower is fueled by the water cycle. The sun evaporates water, which then forms clouds that then drop rainfall and snow that create rivers, streams and other large bodies of water. The famous Hoover Dam, the giant structure holding back the raging Colorado River, is only one example of how hydropower is used today.

Hydropower relies on the kinetic energy from flowing water and transforms it into electricity through spinning turbines located in a moving body of water. Hence, hydropower can be a large-scale operation like the Hoover Dam, or it can be small-scale without a dam. Most importantly, this process doesn’t create greenhouse gases when generating electricity.

6. Nuclear Energy

Nuclear power plant
These water cooling towers are practically a symbol of nuclear energy.

Now, we’re getting into more controversial territory. This is the test case for why “clean” energy is difficult to define for some. Technically, nuclear energy is emissions-free, and it is hugely efficient. One pellet of uranium fuel (approx. 1 cm x 1 cm) is the energy equivalent of approximately 150 gallons of gas or 17,000 cubic feet of natural gas. To put this in perspective, five grams of this tiny pellet can produce enough energy to power a normal household for 6 months.

The counter to that “clean” argument is that nuclear energy gives off radiation, which, if improperly handled, could contaminate air and water. However, even with the horrible outliers like Chernobyl and Three Mile Island, the risk of contamination is small since there are so many safety systems in place.

So, is this energy source truly clean? In our opinion, because of the waste created, nuclear energy is not clean. However, we can’t deny that nuclear power significantly reduces greenhouse gas emissions by replacing the need for fossil fuels. Ultimately, you have to decide for yourself whether this one checks the clean energy box.

7. Natural Gas

Natural gas burns on a stop top
Yep, gas cooktops in our home are a common use of natural gas in our everyday lives.

This is easily the most disputed inclusion on our list. In fact, the Department of Energy doesn’t even list natural gas as a clean energy source. It’s under the fossil fuels section because, fundamentally speaking, natural gas is derived from dinosaurs, and it does produce greenhouse gas emissions, specifically methane, when burned.

So, what’s the point of even considering natural gas on this list? According to the U.S. Energy Information Administration, burning natural gas results in fewer emissions of nearly all types of air pollutants than coal or petroleum products to create the same amount of energy. It’s considered “clean” because it’s technically “cleaner” than other fossil fuels and is the reason for its explosion in popularity amongst energy generators.

However, it definitely has drawbacks, specifically when you consider hydraulic fracking. While we won’t get into the nitty-gritty details behind how this process works, it’s essentially a low-cost way of extracting natural gas from rock. Fracking requires a lot of water, which creates a lot of wastewater, and it’s been known to cause earthquakes and contaminate water supplies.

Sorry, no checkmark for you!

‘Clean’ Coal: The Energy Source We Just Couldn’t Include

Coal mine
A coal excavation site

There have been endless internet memes created about clean coal for a reason: It’s the literal opposite of clean energy.

In reality, clean coal is no different from regular coal. It’s merely a public relations ploy designed to reshape public opinion on fossil fuels. Clean coal is dubbed “clean” because coal plants can capture the carbon dioxide (CO2) before it’s emitted into the air and bury it underground. The process is called carbon capture and storage, and we’re all for it — when implemented correctly.

To whit, carbon capture is a great way to tackle global warming, as it collects CO2 already in the atmosphere and puts it back into the earth. This is essentially what plants do; carbon capture and storage is just a man-made way of doing it.

What we’re not on board with is terming any aspect of the coal industry as “clean.” Coal creates significant environmental impacts beyond just burning it to create electricity. This includes mining, land erosion, acid rain, water pollution and much more.

This doesn’t get a checkmark. We give it a big red “X” — the kind you feared from your teachers in school.

Hopefully Clean Energy is a Little Less Murky

The more research you do into clean energy, the more confusing the term becomes. This is why there’s such a need for an official definition of the concept. That’s why we created one ourselves: Clean energy is any energy source that does not emit greenhouse gases or other pollutants. Hence, nuclear waste isn’t clean by that metric.

Well, isn’t that convenient? By our definition, clean energy really is just another term for renewable energy. Check!