The energy sources most commonly used by industrialized nations are fossil fuels: coal, oil, and natural gas. Energy for manufacturing, transportation, household and commercial electricity all use non-renewable fossil fuels. Renewable energy sources have remained less developed and only reflect 3% of the world’s commercially traded energy.
Reserves are known deposits from which materials can be extracted profitably with existing technology under present economic conditions. Resources are naturally-occurring substances of use to humans that can be extracted using current technology.
Surface mining can be more efficient than underground mining because it removes most of the coal in a vein and can be used profitably for a seam of coal as thin as half a meter. The disadvantage of surface mining is that it disrupts the landscape, and reclamation is expensive and often not successful.
Mining coal is more disruptive to the environment than drilling and extracting oil. Coal mining generates a great deal of dust causing local air pollution. Burning coal releases millions of metric tons of material, carbon dioxide, and acid deposition into the atmosphere. Environmental impacts of oil extraction and use include oil spills and air pollution.
Limiting factors in the development of hydroelectric sites include displacement of people and plant and animal species from the site, loss of farmland, destruction of the natural ecosystem, and a reduction of nutrient-rich silt deposition.
The cost, low energy output, and disruption of the normal estuary limit the development of tidal power. Power plant sites are limited to those sites with the greatest tidal change, such as narrow bays and estuaries which are near the poles.
Geothermal energy is available in areas where molten material from the Earth's core is near enough to the surface to heat underground water and form steam. The United States has about half of the world’s geothermal electrical generating capacity.
The sun heats the Earth's atmosphere and creates air currents that cause wind.
A passive solar system is a design that allows for the entrapment and transfer of heat from the sun to a building without the use of moving parts or machinery. An active system is one that traps sunlight energy as heat energy and uses mechanical means to move it to another location.
Problems with using solid waste include the need for sorting burnables from non-burnables, the need for a large and dependable supply, and the air pollution produced when it is burned.
Energy conservation techniques include the use of fluorescent bulbs, energy-efficient appliances, and low-emissive glass.
