The US consumes about 84 quads per year. World oil reserves are about 10,000 quads. World natural gas reserves are about 7500 quads. Oil shale and tar sand estimated resources are about 13,500 quads. Estimated coal reserves are about 135,000 quads.
Environmental problems exist for all fossil fuel resources.
At the production and transportation stage, oil spills can cause extensive damage to plant and animal life. Coal is produce most economically from large strip mines. 2 O to the atmosphere along with lesser amounts of SO 2 and NOx. Sulfur and nitrogen oxides cause acid rain, and CO 2 is a greenhouse gas. The amount of CO 2 in the atmosphere has been rising over the past 40 years.