By
Grace Smoot

Sustainable energy sources can reduce the effects of global warming by limiting global greenhouse gas (GHG) emissions. Because they are in infinite supply and produce less carbon dioxide (CO₂) emissions than traditional fossil fuels, it is important to understand what they are and how they work. So, we had to ask: What is sustainable energy really, and how could it help us mitigate climate change?

Sustainable energy (solar, wind, micro/low hydropower, geothermal, tidal, and wave) is an energy substitute for fossil fuels that combats climate change, has various environmental benefits, and produces less CO₂ than traditional fossil fuels (between 4.5 and 48 gCO₂ on a life-cycle basis).

Keep reading to find out all about what sustainable energy is, its global capacity, its carbon footprint, its environmental benefits and drawbacks, and how it can combat climate change.

The Big Picture of Sustainable Energy

Sustainable energy encompasses the energy sources that are infinite in supply so long as the rate of harvest remains below the rate of natural replenishment. 

How Is Sustainable Energy Defined

Sustainable energy sources are energy substitutes for fossil fuels (e.g., coal, oil, natural gas) that can reduce the effects of global warming by limiting global greenhouse gas (GHG) emissions whilst preserving the natural integrity of the environment. They meet the needs of our current generation without compromising the ability of future generations to meet their own needs.

“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

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 sustainable energy are all areas where the energies could become unsustainable. 

What Are the Different Types of Sustainable Energy 

The 6 types of sustainable energy are: solar, wind, hydropower (micro/low), geothermal, tidal, and wave energy. 

• Solar energy is the conversion of sunlight into electrical energy either through the use of photovoltaic (PV) panels or solar radiation concentrating mirrors. 

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

Cambridge Dictionary

• Wind energy is the conversion of moving air into electrical energy. It is a form of solar energy that is caused by the uneven heating of the earth’s surface, irregularities of the earth’s surface, and the earth’s rotation. 

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

Cambridge Dictionary

• Hydropower energy is the conversion of moving water into electrical energy through the use of various types of hydroelectric facilities.

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

Cambridge Dictionary

• Geothermal energy is the conversion of heat inside of the earth into electric energy. It is created by the decay of radioactive materials in the rock and fluid of the earth’s core. 

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

Cambridge Dictionary

• Tidal energy is the conversion of the earth’s tides into electrical energy. It is created by the gravitational pull of the sun and moon coupled with the rotation of the earth.

“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

• Wave energy is the conversion of the up and down motion of waves into electrical energy. It is created when the wind blows over the surface of the water on oceans or lakes. 

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

Britannica

These 6 types of sustainable energy could play an important role in mitigating climate change, so let’s have a closer look at them next.

What sustainable energy is	Sustainable energy sources are those that meet the needs of our current generation without compromising the ability of future generations to meet their own needs.
What the different types sustainable energy are	The 6 types of sustainable energy are: solar, wind, hydropower (micro/low), geothermal, tidal, and wave energy.
How sustainable energy works	Sustainable energy works by harvesting the kinetic energy of a specific sustainable energy source, which turns a turbine and spins a generator to produce electricity.
The global capacity of sustainable energy	Global renewable energy capacity is over 3,000 gigawatts. Only a few countries have renewables as their primary energy source, but capacity growth is expected to increase as more effort is put into reducing global GHG emissions to mitigate climate change.
The carbon footprint of sustainable energy	On a life-cycle basis, the carbon footprint of sustainable energy ranges anywhere from 4.5 to 48 grams of CO2 equivalent per kWh (gCO2/KWh) of electricity produced.
The environmental benefits of sustainable energy	Sustainable energy promotes energy independence, creates jobs, produces less CO2 than traditional fossil fuels, and mitigates climate change.
The environmental drawbacks of sustainable energy	Sustainable energy can cause land degradation, habitat loss, threats to terrestrial and aquatic wildlife, changes in water quality, and earthquakes, depending on the source.
Sustainable energy and climate change	Sustainable energy combats climate change because it emits less GHGs than traditional fossil fuels and aims to have minimal impacts on the environment.

How Does Sustainable Energy Work

In general, sustainable energy works by harvesting the kinetic energy of a specific sustainable energy source which turns a turbine and spins a generator to produce electricity. 

How Does Sustainable Energy Actually Produce Energy

More specifically, each sustainable energy source is harvested in different ways.

Solar energy uses either photovoltaic (PV) solar cells or concentrating solar thermal plants (CSP) to produce electricity. The former absorbs energy from sunlight, creating an electrical charge which moves in response to an internal electric field in the cell, causing electricity to flow. The latter reflects and concentrates sunlight onto receivers that collect and convert solar energy into heat. 

• Enough sunlight strikes the surface of the earth in an hour and a half to account for the world’s energy consumption in a year. Because solar energy has such a large electricity generation potential, it is important to understand how it works.

Wind energy is generated when wind turns onshore or offshore wind turbine blades, producing electricity. 

• The global installed capacity of wind energy increased by a factor of 75 between 1997 and 2018, growing from 7.5 GW to over 564 GW. Because wind energy is one of the cheapest and fastest-growing renewable energy technologies with a low carbon emissions profile, it is important to understand how it works.

Hydropower energy is generated when run-of-river, storage, pumped storage, and offshore hydroelectric facilities use flowing water to produce electricity. 

• Because hydropower is one of the oldest forms of renewable energy generation and makes up more than 60% of global renewable energy generation, it is important to understand how it works. 

Geothermal energy is generated when drilling down to hot water reservoirs up to a mile below the surface creates steam which is used to produce electricity.

• Because geothermal systems have a life-cycle global warming emission of approximately 0.2 pounds of carbon dioxide (CO₂) equivalent per kilowatt-hour, compared to 1.4-3.6 pounds for coal, it is important to understand how it works..

Tidal energy is generated when tidal turbines, barrages, and lagoons use the rise and fall of tides to produce electricity.

• Because estimates for the life-cycle global warming emission of tidal energy are below 0.05 pounds of CO₂ equivalent per kilowatt-hour, compared to 1.4-3.6 pounds for coal, it is important to understand how it works.

Wave energy is generated when float/buoy, oscillating water columns, and tapered channel systems use the rise and fall of waves to produce electricity. 

• The market for wave energy is expected to reach $141 million by 2027. Because the generating potential for wave energy is so high, it is important to understand how it works.

What Is the Global Capacity of Sustainable Energy

All sustainable energy is by definition also renewable energy. Renewable energy is infinite by definition because the resources naturally replace themselves over time. It is mostly non-polluting, low-maintenance, and promotes the decentralization of energy supply.

Driven by decreasing costs and improved technology, renewable energy capacity grew over 4 fold from 2000-2021, increasing from 754 gigawatts (GW) to 3,064 GW. This is as more and more effort is put into reducing global GHG emissions to mitigate climate change

However, only a few countries have renewables as their primary energy source, while the vast majority of countries still have a long way to go. Approximately 11% of global primary energy came from renewable energy technologies in 2019. 

What Is the Carbon Footprint of Sustainable Energy

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the GHG emissions associated with consumption, but also includes other emissions such as methane (CH4), nitrous oxide, and chlorofluorocarbons.

“Carbon footprint: the amount of greenhouse gasses and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

On a life-cycle basis, the carbon footprint of sustainable energy ranges anywhere from 4.5 to 48 grams of CO₂ equivalent per kWh (gCO₂/KWh) of electricity produced. 

Type of Sustainable Energy	Carbon Footprint
Solar	Concentrated: 38 gCO2/KWhPV roof: 41 gCO2/KWhPV utility: 48 gCO2/KWh
Wind	Onshore: 11 gCO2/KWhOffshore: 12 gCO2/KWh
Hydropower (Micro/Low)	Low: 4.5-13.6 gCO2/KWh
Geothermal	38 gCO2/KWh
Tidal	22 gCO2/KWh
Wave	Relatively low, but more research is needed

Have a look at the illustration below to see the average life-cycle CO₂ equivalent emissions of the sustainable energy sources and how they compare to the other energy types.

When discussing the carbon footprint of certain sustainable energy types, we must take into account carbon emissions across the energy’s building, operating, and building back phases.

The life-cycle stages of sustainable energy	Each stage’s carbon footprint
Building of sustainable energy	Construction of sustainable energy power plants and electricity delivery mechanisms.
Operating of sustainable energy	Little to no CO2 emissions or waste products
Building back of sustainable energy	CO2 emissions from decommissioning the sustainable energy power plant and subsequent land restoration

Because sustainable energy is becoming a greater part of our energy mix, it is important to understand what its carbon footprint is. And what its environmental benefits and drawbacks are.

How Environmentally Friendly Are Sustainable Energy Sources

The overall environmental friendliness of sustainable energy depends on which specific type of energy is being discussed.

“Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

There are collective, as well as unique, benefits and drawbacks to sustainable energy. 

What Are Environmental Benefits of Sustainable Energy

All 6 sustainable energies have the following environmental benefits:

• Climate change mitigation: The above-mentioned energies have an average life-cycle CO₂ equivalent emission value between 4.5 and 48 gCO₂/KWh, which is much less than, e.g., coal at 820g of CO₂ equivalent per kWh. This reduction in CO₂ emissions, in turn, reduces the effects of global climate change including increasing temperatures, rising sea levels, melting of sea ice, changing precipitation patterns, and ocean acidification.

• Energy independence: Being able to produce our own electricity in the US without the aid of foreign countries is an important step to help us become more self-sufficient. 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). 

• Employment opportunities: The renewable energy sector collectively employed 12 million people worldwide in 2020. Renewable energy jobs continue to increase as we start to realize just how beneficial renewable energy is for our environment. 

There are also specific benefits unique to each sustainable energy type: 

• Solar: Throughout its life cycle, concentrated solar energy produces 0.04%, PV roof solar energy produces 0.05%, and PV utility solar energy produces 0.06% of the CO₂ emissions per unit of electricity that coal produces. 

• Wind: Throughout its life cycle, wind energy produces 0.02% of the CO₂ emissions per unit of electricity than coal produces. And after 3 to 6 months of operation, a wind turbine has effectively offset all emissions from its construction, which means it can operate virtually carbon-free for the rest of its lifetime.

• Micro/low hydropower: Hydropower has the potential to reduce overall GHG emissions by 5.6 gigatons by 2050, which is equivalent to nearly 1.2 billion passenger vehicles driven in a year. This would also save around $209 billion in damages caused by climate change. 

• Geothermal: Throughout its life cycle, geothermal energy produces 5% of the CO₂ emissions per unit of electricity that coal produces. In the US alone, annual geothermal energy resources effectively offset the emission of 4.1 million metric tons (t) of CO₂, 200,000 t of SO₂, 80,000 t of nitrogen oxides, and 110,000 t of particulate matter when compared to conventional coal-fired plants.

• Wave: Tidal and wave energy could help reduce global CO₂ emissions from fossil fuel electricity generation by around 500 million tons by the year 2050. 

What Are Environmental Drawbacks of Sustainable Energy

Each sustainable energy type comes with its own set of environmental drawbacks that should be taken into account when discussing its carbon footprint. 

• Solar: The scale of land degradation and habitat loss depends on the technology, site topography, and intensity of the solar resource. Siting large-scale solar farms on abandoned land and small-scale farms on top of buildings or homes can minimize negative environmental impacts. Water is used for the construction of PV components, and CSPs require water for cooling. Hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride, 1,1,1-trichloroethane, and acetone are all used to manufacture PV cells. If not handled and disposed of properly, these hazardous materials could present a serious risk to environmental and public health.

• Wind: Wind farms use a substantial amount of land, but the areas between and around turbines can be used for livestock grazing, agriculture, highways, and hiking trails. Turbine blades are large and can pose a threat to flying wildlife such as birds and bats. Extensive research and technological advances have reduced turbine-caused wildlife death. Turbines can also cause mechanical and aerodynamic noise pollution when constructed close to residential areas. Siting wind farms in remote locations or on abandoned lands can reduce this effect.

• Micro/low hydropower: Hydropower can affect aquatic organisms by interfering with fish migration, blocking movement up/downstream, and altering water flow patterns and quality conditions. Hydropower reservoirs can retain so much water that the water body below the dam dries up. Diversion projects take water away from the river and return it to the river downstream. The water released from the dam may experience changes in temperature and dissolved oxygen concentration. 

• Geothermal: Geothermal reservoirs occur deep underground and are not detectable from the surface. Areas where geothermal does come to the surface are only found near tectonic plate boundaries. Also, high-pressure fluid injections close to neighboring fault lines have the potential to trigger earthquakes. 90% of all earthquakes occur in the Ring of Fire, an area that coincides with the highest concentration of geothermal resources. 

• Wave: The main environmental concern with wave energy is the impact on aquatic wildlife. Construction and operation of marine energy technology may negatively impact estuarine ecosystems via underwater noise pollution, habitat changes, and wildlife collisions with turbines. Because wave energy is a relatively new technology, more research needs to be done to fully understand this environmental impact.

Why Is Sustainable Energy Important to Fight Climate Change

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 sustainable energy (solar, wind, hydropower, geothermal, tidal, and wave 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 cut current GHG emissions by 50% by 2030 and reach net zero by 2050, as outlined in the 2015 Paris Climate Agreement.

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. 

Final Thoughts

Harnessing the kinetic energy of sustainable energy (solar, wind, micro/low hydropower, geothermal, and wave energy) spins a turbine and powers a generator to produce electricity. The capacity for sustainable energy is great, but few countries currently source most of their energy from sustainable sources. 

Sustainable energy has a lower carbon footprint than fossil fuels, combats climate change, creates jobs, and promotes energy independence, making it an environmentally friendly energy source. Any environmental concerns can all be mitigated by careful siting of power plants and proper disposal of any waste materials. Sustainable energy benefits both our atmosphere and Earth’s biota.

Stay impactful,

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