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A guide to green energy and renewable sources

Caitlin Ritchie
By Caitlin Ritchie September 5th, 2019
6 min read

What are ‘renewable resources’?

According to the Organization of American States, renewable resources are “energy resources and technologies whose common characteristic is that they are non-depletable or naturally replenishable.” Green energy, on the other hand, comes from renewable resources and results in little to no carbon impact.

Consumption of green energy and other sources.

As an example, think about solar energy – while it may not be sunny every day, there is no limit on the amount of sunshine we can receive, so the energy that we can generate from solar panels is “non-depletable or naturally replenishable.”

An example of a renewable resource that isn’t green is one of the oldest energy sources in the world – wood. Humans have been using wood as a source of light and heat for thousands of years. To this day, wood is considered renewable because trees are naturally replenishable (especially with a little help from humans).

See how green energy has become more prominent.

Types of renewable resources:

There are several types of renewable resources. Read about several different types below:


The term “biomass” simply means energy that comes from plants and animals. The U.S. Energy Information Administration explains why biomass is useful: “Biomass contains stored energy from the sun. Plants absorb the sun’s energy in a process called photosynthesis. When biomass is burned, the chemical energy in biomass is released as heat.”

Solid forms of biomass include wood, crops and animal manure, both of which could be burned for heat and fuel. Alternatively, biomass can also be turned into biogas or biofuels – these can also be burned for energy.





Following are the top 10 states in generating electricity from wood and other biomass, in thousand megawatt hours:

Here’s the “but.” Burning biomass releases carbon dioxide into the air, which can be harmful to the environment. Carbon dioxide is a greenhouse gas also released by nonrenewable resources and contributes to global warming. However, plants that create biomass also absorb carbon dioxide through photosynthesis. Some lawmakers insist the process is carbon neutral, but scientists disagree.


A large portion of renewable energy generated in the U.S. comes from wind power. Historically, we used windmills to pump water. Now, we rely on wind turbines, which are essentially giant pinwheels that collect the wind’s energy. When the wind blows, the turbine’s blades rotate. Those turbines are connected to electric generators, so the movement from the wind generates electricity.

Texas leads the country in wind power, producing nearly 28 percent of the nation’s electricity from wind as of June 2019. Following Texas in wind production is Oklahoma and Iowa.

Wind is a renewable resource because it occurs naturally and will never run out. Wind turbines are considered green energy alternatives because they don’t release harmful emissions or pollutants into the air or water and have a minimal impact on the ecosystem. That being said, wind can be inconsistent and a day without wind means less energy will be generated. For example, the U.S. produced 11.6 percent less electricity in June 2019 than in May.

Following are the top 10 states generating wind power, in thousand megawatt hours:


It may sound like a superhero power, but hydropower is simply energy created by moving water. Sources of water (such as rivers, lakes and waterfalls) have the potential to generate electricity – or hydroelectric power – through movement.

Like wind turbines, hydroelectric power is produced when flowing or falling water turns the blades of a turbine, which is connected to a generator. Water can be funneled through pipes or dams to effectively turn the turbine blades.

There are a few concerns about the environmental impact of hydropower. Building dams can negatively affect the ecosystem of a location, while some dams create reservoirs – such as lakes and ponds– that emit greenhouse gases including carbon dioxide and methane. However, hydropower remains an efficient green energy option because of hydropower plants don’t rely on fossil fuels to operate and produce electricity using a renewable resource.


Following are the top 10 states in generating electricity from hydropower, in thousand megawatt hours:


Solar power is energy produced by the sun. Solar power relies on devices that convert sunlight into electricity, the most well-known being the solar panel. Sunlight is made of photons, which are particles of energy. When absorbed by a device like a solar panel, we can turn these photons into electricity.

California leads the U.S. in solar energy production, generating more than 40 percent of the country’s solar power as of June 2019. Trailing California are Arizona and North Carolina.

Solar energy systems do not negatively impact the environment or produce harmful air or water pollution. One drawback is that the weather is inconsistent from day to day. Because of this inconsistency, solar energy generation fluctuates from day-to-day. For example, U.S. solar energy production increased more than 9 percent

Following are the top 10 U.S. states generating solar energy, in thousand megawatt hours:


To put it simply, geothermal energy is heat generated within the earth and is renewable because the earth never stops producing this heat. Geothermal energy is produced naturally through volcanoes, hot springs and geysers and is incredibly powerful – scientists have determined the earth’s inner core is as hot as the surface of the sun!

There are a few different ways to harness geothermal energy, but the most impactful method in the U.S. is geothermal electricity generation. Using incredibly hot water or steam, geothermal power plants can generate electricity. The U.S. leads the world in geothermal power plants, with California producing more than 70 percent of the country’s geothermal electricity.

According to the EIA, geothermal power plants emit 99 percent less carbon dioxide than fossil fuel power plants. Geothermal energy is also consistent and reliable, making it a stable form of green energy. As is the case with other forms of renewable energy, building geothermal power plants can impact the ecosystem of the landscape. However, many geothermal features occur naturally and are key features in the landscape’s ecosystem, such as the Old Faithful geyser in Yellowstone National Park.

Following are the seven states that generate electricity from geothermal sources, in thousand megawatt hours:

Why does this matter?

Scientists warn that climate change and global warming will continue to worsen in the near future. Recent reports predict we have 18 months to cut carbon emissions by 45 percent or risk permanent damage to the environment.

More than 75 percent of the carbon dioxide produced in 2016 – the most recent year for which statistics are available – came from burning fossil fuels and other nonrenewable resources. Carbon dioxide contributes to the “greenhouse effect,” which NASA explains is “warming that results when the atmosphere traps heat radiating from Earth toward space.” The greenhouse effect is a leading factor in global warming.

To put it bluntly, renewable and green energy resources are important because fossil fuels are incredibly harmful to the environment. By opting for green energy plans using renewable resources, each household can slow down the harmful effects of nonrenewable resources and contribute to a healthier Earth.

To learn more about green energy options and see where your state ranks for wind, solar or carbon dioxide production, visit our Choose Energy Data Center.

Caitlin Ritchie is a writer within the energy and power industry. Born in Georgia, she attended the University of Georgia before earning her master’s in English at the University of North Carolina at Charlotte.

Image credit/Shutterstock

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