Fossil Fuels
Fossil fuels come from the organic matter of plants, algae, and cyanobacteria that were buried, heated, and compressed under high pressure over millions of years. The process transformed the biomass of those organisms into three types of fossil fuels: oil, coal, and natural gas.
Petroleum (oil)
Thirty-seven percent of the world’s energy and 43% of the United States’s energy consumption comes from oil. Scientists and policy-makers often discuss when the world will reach peak oil production, the point at which oil production is at its greatest and then declines. It is generally thought that peak oil will be reached by the middle of the 21st Century, although making such estimates is difficult because many variables must be considered. Worldwide reserves are 1.3 trillion barrels or 45 years left at the current production level.
Environmental Impacts of Oil Extraction and Refining
Oil is usually found one to two miles (1.6 – 3.2 km) below the Earth’s surface, whether on land or ocean. Once the oil is found and extracted, it must be refined, which separates and prepares the mix of crude oil into the different types for gas, diesel, tar, and asphalt. Oil refining is one of the top sources of air pollution in the United States for volatile organic hydrocarbons, toxic emissions, and the single largest source of carcinogenic benzene. When petroleum is burned as gasoline or diesel, or to make electricity or to power boilers for heat, it produces a number of emissions that have a detrimental effect on the environment and human health:
- Carbon dioxide (CO2) is a greenhouse gas and a source of climate change.
- Sulfur dioxide (SO2) causes acid rain, which damages plants and animals that live in water and increases or causes respiratory illnesses and heart diseases, particularly in vulnerable populations like children and the elderly.
- Nitrous oxides (NOx) and Volatile Organic Carbons (VOCs) contribute to ground-level ozone, an irritant that causes lung damage.
- Particulate Matter (PM) produces hazy conditions in cities and scenic areas and combines with ozone to contribute to asthma and chronic bronchitis, especially in children and the elderly. Very small, or “fine PM,” is also thought to penetrate the respiratory system more deeply and cause emphysema and lung cancer.
- Lead can have severe health impacts, especially for children.
Other domestic sources of oil are being considered conventional resources and are being depleted. These include tar sands – moist sand and clay deposits with 1-2 percent bitumen (thick and heavy petroleum-rich in carbon and poor in hydrogen). These are removed by strip mining (see section below on coal). Another source is oil shale, which is sedimentary rock filled with organic matter that can be processed to produce liquid petroleum. Extracted by strip mining or creating subsurface mines, oil shale can be burned directly like coal or baked in hydrogen to extract liquid petroleum. However, the net energy values are