Clean Energy Fuel What Are They?

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Clean energy fuel definitions can greatly vary depending on who you ask

Clean energy fuel definitions vary, depending on who you ask or where you look to for an answer. Some people think natural gas is a clean burning energy source and it is widely advertised as being “clean”, however it is not clean by any means. When we look at the power plant, the burning of natural gas produces nitrogen oxides and carbon dioxide, but in lower quantities than burning coal or oil.

Methane (CH₄) is a primary component of natural gas and a highly potent greenhouse gas which can also be emitted into the air when the gas is not burned properly and completely. Similarly, methane can be emitted as the result of leaks and losses during transportation. Emissions of sulfur dioxide and mercury compounds from burning natural gas are negligible.

Methane remains in the atmosphere for approximately 9-15 years and is 25 times more effective in trapping heat in the atmosphere than carbon dioxide (CO₂) over a 100-year period and 72 times more potent over a 20 year period. It is emitted from a variety of natural and human-influenced sources. The human-influenced sources include landfills, natural gas and petroleum systems, agricultural activities, coal mining, stationary and mobile combustion, waste-water treatment, and certain industrial processes.

The average emissions rates in the United States from natural gas-fired power generation are as follows:


Natural Gas Emissions Table

Emission Material:

Emission Rate:

Carbon Dioxide (CO₂) 1135 lbs/MWh
Sulfur Dioxide (SO₂) 0.1 lbs/MWh
Nitrogen Oxides (N₂O) 1.7 lbs/MWh


Compared to the average air emissions from coal-fired power plants, this gas produces half as much carbon dioxide, less than a third as much nitrogen oxides, and one percent as much sulfur oxides at power plants. Additionally, the extraction process, treatment, and transportation of the gas to the power plant also generate additional emissions. Fracking to extract the gas is also highly controversial, and is at this point considered by most environmentalists as a bad thing for the environment and local residents.

Clean Energy Fuel




Hydrogen Renewable Water Vapor – Hydrogen
Natural Gas Non-Renewable (See Above Table)
Propane Non-Renewable 20% to 90% Reductions in CO
Biodiesel Renewable CO₂ B20 11% Reduction

B100 78.5% Reduction

Ethanol Renewable Ranges from 19% to 86% less CO₂ emissions than gasoline
Solar Renewable None
Wind Renewable None
Tidal Renewable None
Wave Renewable None
Nuclear Non-Renewable 13 g/kWh
Geothermal Renewable None


CO2 Emissions By Fuel

CO2 Emissions By Fuel

All of the fuels listed in the table above are all better for the environment, but most also come with some drawbacks as well. We mentioned the problems with natural gas, and as we have seen from Japan over the past year or so, nuclear also has issues. They also have other emissions, but we limited those to CO₂ emissions primarily for the purpose of this article making the term “clean” come into question, and it should be redefined to only include truly clean burning energy sources, and place the rest in the alternative energy category.

Our current president, Barack Obama even has a broad definition of the term: “Obama’s definition of ‘clean energy’ is broad one”.

President Obama wants 80 percent of the nation’s electricity to come from clean energy sources by 2035. Achieving this, he says, will take a mix of solar, wind, nuclear, and even fossil fuels like natural gas and coal.

It may also take a liberal definition of “clean.”

Obama’s plan is to force the generation of electricity from coal and natural gas, which together account for 70 percent of the nation’s fuel mix, to get cleaner. At the same time the government would spur the growth of nuclear power and renewables like wind and solar.

The president also pointed to biofuels as a way to “break our dependence on oil” and predicted the country would have one million electric vehicles on the road by 2015.

But what exactly will be considered clean or dirty is not yet known. The answers will depend on whether the concern is greenhouse gases like carbon dioxide or hazardous chemicals like mercury and sulfur dioxide, or, most likely, some combination of both.

It will also depend on whether the environmental hazards caused by mining coal or uranium, drilling for gas or plowing new fields to grow biofuel crops will be considered along with the hazards of burning them for power.

How “clean” is ultimately defined by the administration and Congress will determine how the nation’s energy mix changes over the coming decades — if at all.

Other cleaner fuels in the table have to depend on some other uncontrollable external factors for power, such as the wind, sun, waves, tides which makes them somewhat questionable and not 100% dependable like coal or oil. If we combine them together though, then we could achieve our goal to minimize climate change to 2° C and avoid some of the catastrophic climate change events associated with our reaching higher than the 2° C currently marked by experts in the field.

One other point to consider is the life cycle of fossil fuels, which are approaching their final stages. Oil is becoming harder to find, and the new sources we do find are becoming increasingly difficult and more expensive to extract, and coal will wind up becoming similar in nature and more expensive. Another point to consider is some may also consider the new ‘clean coal myth‘, primarily sponsored by, you can probably guess this one, the Coal Industry! However you choose to look at it, there is nothing clean about coal, nor will there ever be, but it can be burned cleaner than what most power plants are producing today, but at a much higher cost, which would make solar and wind and other cleaner sources of energy much more attractive to both power companies and consumers alike. Either way, even with subsidies at the current levels, fossil fuels will become more expensive as time goes by, making alternatives much more attractive and affordable, and with advancing technologies, that may happen sooner rather than later!

With our list of clean energy fuel and brief description, we hope we have answered all of your questions regarding these types of fuels as we move forward.

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