Physical Science Ch. 9: Energy Sources

The largest portion of our energy needs is supplied with fossil fuels The largest portion of our energy needs is supplied with fossil fuels. However, since these are limited in supply, alternative energy sources will be needed to satisfy our growing U.S. population.

Fossil Fuels Fossil fuels are hydrocarbons (compounds composed of H and C) which are made up of decayed remains of plants and animals. About 85% of all energy used in the U.S. comes from fossil fuels. Q. Stop and Think: Are fossil fuels renewable resources?

Fossil fuels are considered nonrenewable resources - not naturally replaced as quickly as they are used. In order to be renewable, it would need to be replaced nearly as quickly as it is used, like solar power.

Petroleum Petroleum (crude oil) is a liquid fossil fuel. It comes out of the ground as crude oil, and is then separated into different petroleum products by a process called fractional distillation. (refining crude oil into usable products) These products include: natural gas, kerosene, gasoline, heating oil, diesel fuel, and lubricating oil.

The U.S. imports over 50% of it's petroleum from foreign countries. As a result, a sizeable portion of our economy depends on regions which are quite often politically unstable.

Coal Coal is a solid fossil fuel. Coal must be either strip mined or subsurface mined It is used as a fuel primarily in industries (steel mills, power plants, etc.). It produces pollutants when it is burned.

Strip Mining Strip mining uses large scrapers to remove the surface layers of the earth to get at layers of coal which are close to the surface. Strip (or surface) mining is used when layers of coal are close to the surface.

Strip mining is a relatively safe, simple and inexpensive means of collecting coal. However, it is harmful to the environment. It removes vegetation and habitat, and leads to excessive run-off which can erode the land.

Sub-surface Mining Sub-surface mining is where vertical and/or horizontal shafts are dug into the earth to access underground coal deposits.

Sub-surface mining is better for the environment, but is more expensive and more dangerous for the miners. Mine collapses and "black lung" are not uncommon.