By
Grace Smoot

Despite sometimes being used interchangeably, “renewable” and “sustainable” have different definitions which are important to understand when discussing our current climate crisis. Upon closer examination, these differences have varying implications on our environment. So we had to ask: What’s the difference between renewable and sustainable energy?

Renewable energy is the generation of energy from sources that can be replenished naturally over time. Sustainable energy is the generation of energy from sources that can replenish themselves faster than they are depleted. Knowing the differences between the two aids in the fight against global climate change.

So, can energy be both renewable and sustainable? Why is some energy classified as renewable but not sustainable, and vice versa? And which specific energy sources are a part of each? Keep reading to find the answers to all these questions as we’ll walk you through the differences between renewable and sustainable energy and why they matter.

How Are Renewable Energy and Sustainable Energy Defined

A common assumption is that “renewable” and “sustainable” are synonyms. They both aim to reduce global greenhouse gas emissions (GHGs) and mitigate climate change, but the differences in their definitions have different implications on our environment. 

What Does the Dictionary Say About Renewable Energy and Sustainable Energy

Renewable and sustainable energy sources are alternatives to fossil fuels and aid in the fight against global climate change because they help curtail GHGs. Knowing the difference between the two terms allows us to make better-informed decisions regarding our present and future energy usage.

“Renewable Energy: energy that is produced using the sun, wind, etc., or from crops, rather than using fuels such as oil or coal | types of energy that can be replaced naturally such as energy produced from wind or water”

Cambridge Dictionary

Renewable energy can be sustainable if the rate at which we harvest the resource remains below the rate at which the resource can naturally replenish itself. When we begin harvesting resources faster than they can be replenished, renewable energy becomes unsustainable. 

“Sustainable: The ability to be maintained at a certain rate or level | Avoidance of the depletion of natural resources in order to maintain an ecological balance”

Oxford Dictionary

Sustainable energy sources meet the needs of our current generation without compromising the ability of future generations to meet their own needs. They aim to limit GHGs while preserving the natural integrity of the environment.

To sum it up, renewable energy sources are flow-limited because there is a limited amount of energy available per unit of time. Renewable energy is sustainable as long as the rate of harvest stays below the rate of natural replenishment. 

What Do These Differences Mean

The differences in the definitions of renewable energy and sustainable energy have different ramifications on our environment:

• If energy is only renewable but NOT sustainable: The energy source is in infinite supply, but the rate at which we harvest the resource is higher than the rate at which the resource can naturally replenish itself.

• If energy is only sustainable but NOT renewable: This category does not exist because all sustainable energy is, by definition, also renewable energy.  

In short, renewable energy can be sustainable if the natural rate of resource replenishment is greater than the rate of resource utilization. But if not, then the energy becomes unsustainable. 

What Are the Differences and Similarities Between Renewable Energy and Sustainable Energy

Knowing which category each of the following energy types belongs to is important when discussing our present and future energy usage. Using energy sources that meet both the “renewable” and “sustainable” criteria can help reduce the amount of GHGs entering the atmosphere and preserve the natural state of the environment. 

Energy type	Energy source
Both Renewable Energy and Sustainable Energy	Solar, Wind, Micro/Low Hydropower, Geothermal, Tidal, Wave
Only Renewable Energy but not Sustainable Energy	Biomass, Large Hydropower
Only Sustainable Energy but not Renewable Energy	–
Clean energy that is neither Renewable nor Sustainable	Nuclear

Although all sustainable energy is also renewable energy, the reverse cannot be said. 

After researching the amount of the resource available and the rate of resource utilization, we can effectively categorize the following nine energy sources as either renewable and sustainable, only renewable, or neither. 

Which Energies are Both Renewable Energy and Sustainable Energy

If energy is both renewable AND sustainable, the energy source is in infinite supply, and the rate of resource harvest is less than the rate of natural resource replenishment.

Here are the energy sources that are both renewable and sustainable:

“Solar Energy: energy that uses the power of the sun to produce electricity”

Cambridge Dictionary

• Solar energy: The conversion of sunlight into electrical energy either through the use of photovoltaic (PV) panels or solar radiation concentrating mirrors. The energy produced is then used to generate electricity or can be stored in batteries or thermal storage for use at a later time. The three main types of PV solar cells are silicon, thin-film, and III-V solar cells. The three main types of concentrating solar thermal power plants are linear, dish/engine, and power tower systems.

Solar energy is a renewable energy source because solar energy can be harnessed as long as the sun continues to shine. It is also sustainable because it has minimal GHGs and does not negatively affect the environment, provided that proper siting and disposal methods are followed.

“Wind: a current of air moving approximately horizontally, especially one strong enough to be felt”

Cambridge Dictionary

• Wind Energy: Wind turns turbine blades around a rotor, which spins a generator to create electricity. An average annual wind speed of 9 miles per hour (mph) or 4 meters per second (m/s) for small turbines and 13mph (5.8m/s) for utility-scale turbines is necessary to economically harness wind energy. The two main types of wind energy are onshore wind energy and offshore wind energy. The former has lower construction, transportation, maintenance cost, and infrastructure needed to transmit electricity than the latter. The two types of wind turbines are Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT). The largest commercial turbines consist of 780 foot (240 m) tall towers and 530 foot (162 m) long blades that can generate anywhere from 4.8 to 9.5 MW of power. 

Wind energy is a renewable energy source because as long as the wind blows, its power can be harnessed. It is also sustainable because it does not emit greenhouse gases and land use, wildlife impact, and public health concerns are mitigated by proper planning and siting of wind farms.

“Geothermal: involving or produced by the heat that is inside the earth”

Cambridge Dictionary

• Geothermal Energy: The decay of radioactive materials in the rock and fluid of the earth’s core produces geothermal energy. Drilling down to hot water reservoirs up to a mile below the surface creates steam that rotates a turbine, which spins a generator to generate electricity. Geothermal is found along major tectonic plate boundaries where volcanoes are located. The three main types of geothermal power plants are dry steam, flash steam, and binary steam. 

Geothermal energy is renewable because the Earth has an almost unlimited supply of heat generated by its core. It is also sustainable because it produces low levels of GHGs and does not adversely affect the environment. 

“Hydropower: hydroelectric power (= the production of electricity by the force of fast-moving water)”

Cambridge Dictionary

• Hydropower Energy: To harness energy from water, flowing water turns turbines and spins a generator to generate electricity. Micro hydropower generates 100 kilowatts (kW) or less of power, and low-impact hydropower (Low Hydro) generates between 100 kW and 10 MW. 

Hydropower is renewable because the water cycle is a continuous process that recharges itself. It is also sustainable because it produces fewer GHGs than large hydro and has a minute environmental impact.

“Tidal Power: power that comes from the movement of the tide (= the rise and fall of the ocean that happens twice every day) and that can be used especially for producing electricity”

Cambridge Dictionary

• Tidal Energy: The gravitational pull of the sun and moon coupled with the rotation of the earth creates tides in the ocean. A minimum tidal range of 10 feet is required to harness tidal energy economically. The three types of tidal energy technology are stream, barrage, and lagoon systems which use the rise and fall of tides to spin a generator to produce electricity

Tidal energy is renewable because the rotation of the earth and the gravitational pull of the sun and moon will continue until the end of time. Overall, lagoons are the most sustainable form of tidal energy, followed by tidal streams and lastly by barrages. 

“Wave Power: electrical energy generated by harnessing the up-and-down motion of ocean waves”

Britannica

• Wave Energy: Waves are formed when the wind blows over the surface of the water on oceans or lakes. 95% of the wave’s energy is stored between the surface of the water and the top 1/4th of the wave’s length. The three types of wave energy technology are float/buoy, oscillating water column, and tapered channel systems. They use the rise and fall of waves to produce electricity. 

Wave energy is renewable and believed to be sustainable because as long as the sun shines, waves are produced and can be used to generate power. 

Which Energies Are Only Renewable Energy But Not Sustainable Energy

If energy is only renewable but NOT sustainable, the energy source is in infinite supply, but the rate of resource harvest is greater than the rate of natural resource replenishment.

Here are the energy sources that are only renewable but not sustainable:

“Biomass: natural materials from living or recently dead plants, trees and animals, used as fuel and in industrial production, especially in the generation of electricity”

Oxford Dictionary

• Biomass Energy: Biomass is renewable organic material that comes from plants and animals. It is incredibly versatile and can be used to produce fuel, energy, and everyday products that contain plastics. To harvest biomass energy, wood, agricultural crops, biogenic materials, animal manure, and human sewage are burned or are converted to release stored chemical energy from the sun. Biomass can be used to produce biofuels, biopower, and bioproducts. 

Biomass energy is a renewable energy source because it can be replenished by planting trees and agricultural crops. But it is not sustainable because the rate of plant harvest often exceeds the rate of plant growth. It could take anywhere from decades to well over a century before we start receiving the climate benefits provided by biomass, which is well outside the timeframe of averting our current climate crisis. Also, per kWh, biomass power plants emit 150% the carbon dioxide (CO₂) of coal and between 300% – 400% the CO₂ of natural gas, making them a major contributor to climate change. 

“Hydropower: hydroelectric power (= the production of electricity by the force of fast-moving water)”

Cambridge Dictionary

• Hydropower Energy: To harness energy from water, flowing water turns turbines and spins a generator to generate electricity. Large hydropower (Large Hydro) generates 30 MW or more of power. 

Large hydro is renewable because the water cycle is a continuous process that recharges itself. But it is not sustainable because it can potentially alter the natural state of the environment via interfering with fish migration, blocking aquatic movement up/downstream, and altering temperature and dissolved oxygen concentration. Also, Vegetation inundation and decomposition in hydropower reservoirs can release GHG emissions in the form of both CO₂ and CH₄. CH₄ has a global warming potential 28-34 times that of CO₂ and can make up 80% of the emissions from dam reservoirs, as a study from Washington State University found. 

Which Clean Energies Are Neither Renewable Energy Nor Sustainable Energy

If energy is NEITHER renewable NOR sustainable, the energy source is finite in supply, the rate of resource harvest is greater than the rate of natural resource replenishment, or both.

Here are the clean energy sources that are neither renewable or sustainable: 

“Nuclear Power: the power produced when the nucleus (= central part) of an atom is divided or joined to another nucleus”

Cambridge Dictionary

• Nuclear Energy: The two ways to generate nuclear power are nuclear fusion and nuclear fission. In the former, atoms are combined or fused to create larger atoms. In the latter, electromagnetic radiation is used to split the nucleus of a uranium atom, which releases an enormous amount of energy. 

Nuclear energy is not renewable or sustainable because nuclear power plants use the second most common isotope of Uranium (U-235) which has a relative abundance of only 0.7%. Most of the original U-235 on earth has already decayed because it has a half-life of about 700 million years.

Just because nuclear energy isn’t renewable or sustainable doesn’t mean that it isn’t a viable substitute for fossil fuels though. Nuclear energy is classified as clean energy because no greenhouse gases are emitted during its operation. Clean energies play a vital role in combating climate change because they have such low levels of CO₂ emissions.

Why Is it Important to Differentiate Difference Between Renewable Energy and Sustainable Energy

	Renewable Energy	Sustainable Energy
Benefits	Infinite energy supply, promotes decentralization; potentially no greenhouse gas emissions and non-polluting	Limited GHG emissions, non-polluting, climate mitigation benefits, preservation of natural resources
Drawbacks	Some have intermittent production, geographic limitations, lower quantities of energy produced	–

Renewable energy is by definition infinite because the resources naturally replace themselves over time. It is also mostly non-polluting, low-maintenance, and promotes the decentralization of energy supply. On the flip side, renewable energy comes with intermittent energy production, geographic limitations, and lower immediate quantities of energy compared to non-renewable energy sources (e.g., coal and oil). 

Sustainable energy aims to limit GHG emissions while preserving the natural integrity of the environment. An energy source can be sustainable as long as the rate of resource harvest stays below the rate of natural resource replenishment. Harvesting, utilizing, operating, and building infrastructure for renewables are all areas where the energies could become unsustainable. 

How Do Renewable Energy and Sustainable Energy Benefit the Environment

Fossil fuel combustion is the main contributor to atmospheric CO₂ levels. Climate Change occurs when CO₂ and other air pollutants absorb sunlight and solar radiation in the atmosphere, trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). The current global annual temperature rise is 0.18C, or 0.32F, for every 10 years. 

Using renewable and sustainable energy instead of fossil fuel energy helps mitigate the following negative effects of climate change:

• Increasing temperatures: Earth’s atmosphere has warmed 1.5℃ since 1880. This may not seem like a lot, but these degrees create regional and seasonal temperature extremes, reduce sea ice, intensify rainfall and drought severity, and change habitat ranges for plants and animals.

• Rising sea levels: Global sea levels have increased approximately 8-9 inches since 1880, displacing people living along coastlines and destroying coastal habitats. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, and landfills remain at risk if sea level rise goes unchecked. 

• Melting of sea ice: Since 1979, arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 

• Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.

• Ocean acidification: The ocean absorbs 30% of the CO₂ released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must limit global warming to 1.5C by 2040. 

The more we reduce CO₂ emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

Renewable energy and sustainable energy also benefit the environment in the following two ways: 

1. Energy Independence: Being able to produce our own electricity in the U.S. without the aid of foreign countries is an important step to help us become more self-sufficient instead. Former President George W. Bush signed the Energy Independence and Security Act of 2007 to reduce U.S. dependence on oil, expand the production of renewable fuels (and confront global climate change). 

2. Employment Opportunities: The renewable energy sector employed 11.5 million people worldwide in 2019. Renewable energy jobs continue to increase as we start to realize just how beneficial renewable energy is for our environment. 

We still have a long way to go to make clean or renewable energy sources our primary form of energy. Only a very few countries have renewables as their primary energy source, while the vast majority of countries are still far off. Renewable energy only accounted for 11% of total energy consumption in the United States in 2019. But experts predict renewable resource consumption will continue to increase through 2050 as more and more effort is put into reducing global greenhouse gas emissions.

Final Thoughts

All sustainable energy is by definition also clean renewable, but the reverse is not always true. Renewable energy means the resource is infinite in supply, and sustainable energy means that the rate of resource harvest is below the rate of resource replenishment. When discussing climate change, it is important to differentiate between the two.  

Solar, wind, micro/low hydropower, geothermal, tidal, and wave energy are all both renewable and sustainable, whereas biomass and large hydro energy are renewable but not sustainable. Nuclear power is a clean energy that is neither renewable nor sustainable, but this doesn’t necessarily make it a bad choice when discussing substitutes for fossil fuels! Other factors must be considered, including GHG emissions.

Stay impactful,

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