If a source of energy is renewable, that doesn’t mean it produces little or no greenhouse gas emissions. It can be toxic, hazardous, or environmentally catastrophic. A renewable source is basically something that can’t be used up because it can be recreated somewhat quickly.

Fossil fuels and nuclear aren’t renewable because these fuels were created millions of years ago.  Meanwhile, wood, ethanol, biodiesel, agriculture waste, and methane from cows are considered renewable, even though using these for fuels generates plenty of carbon dioxide. Some of them, like wood, produce hazardous airborne particulates, too.

The difference is that these renewable energy fuels came from plants that grew relatively recently. Proponents argue that growing new plants for the next cycle of fuel will trap carbon dioxide from the first cycle’s emissions. In practice, this argument doesn’t always hold, for various reasons. In some regions, dense carbon-trapping rainforest was removed to grow a single layer of plants for biofuel production, creating a net increase in carbon dioxide that will not be compensated. Also, biofuels are processed and transported using forms of energy that are largely still fossil-based. Furthermore, using food plants for fuel increases the food prices and has already resulted in food shortages abroad.

Some renewable fuels do a better job of having a closed cycle of plants to fuel to plants than others, but most government incentives and rules don’t prefer one kind to another. And some rules designed to support methane production from biological sources like agriculture end up benefiting natural gas producers that drill for methane (natural gas) produced millions of years ago.

Of course, renewable fuels like wind, sun, geothermal, and ocean energy don’t rely on agriculture at all.


Sources of energy that do not produce significant greenhouse gas during generation include geothermal, wind, ocean energy, nuclear, hydroelectric, and solar. Nonetheless, except ocean, wind, and a special type of solar called photovoltaic, all of these “zero emission” sources require energy-dependent water to cool them or to run steam turbines. Some rely on petroleum fuels for construction and workers’ transportation, especially for remote wind and solar installations. Nuclear energy produces nuclear waste.

If reducing greenhouse gas emissions is a national goal, it’s important to get the whole picture of a source of energy, from sourcing a fuel to what happens to the byproducts. All renewable sources of energy are not equal.


All sources of energy have an effect on the plant and animal world. Though they avoid carbon or toxics emissions, tidal energy and hydroelectric power plants can interfere with the movements of fish and other aquatic life. Ocean thermal power plants can disturb the temperature distribution in water, which can be detrimental to aquatic life.

Solar and wind power needs lots of land area, which can disrupt wildlife. Windmills kill birds and bats sometimes. Solar thermal uses water for turbines, and that can be a problem if a solar plant is located in a desert. Solar photovoltaic use nasty chemicals for producing the solar panels.

Nonetheless, fossil fuels are probably, by any measure, far less environmentally responsible. All of them add more carbon dioxide into the atmosphere, contributing to greenhouse gas emissions.

Coal is the most notorious source. It adds to airborne particulate matter, mercury contamination of water, and sulfur oxides and nitrous oxides –which contribute to acid rain. Coalmines are destructive to humans, water sources, and the natural environment. However, coal power plants have been hit with increasingly strict emissions rules, and American coal in general is cleaner than other coal sources worldwide. Coal is an even bigger environmental hazard abroad, like in China.

Burning natural gas is much cleaner than coal, and if burned in combined cycle power plants, natural gas produces less carbon dioxide than coal. However, the new technology of hydrofracking for shale gas is thought to cause widespread groundwater contamination.

Petroleum also emits carbon dioxide when it’s used, and it comes with particulate matter. Every year there are countless oil fires, oil spills and drilling accidents, some small and some on the scale of the 2010 Deepwater Horizon in the Gulf of Mexico.