Fuels in the transportation sector are, for the most part, derived from petroleum. At each step in the energy cycle, there are impacts on the environment. Drilling for oil and gas obviously has consequences for the surrounding land, or water, in the case of offshore drilling. Extraction of coal impacts the land and may contaminate underground water tables. Mining and milling of uranium ore produce large quantities of radioactive materials which must be dealt with.
Useful work is obtained from energy resources by converting the energy from one form to another.
Heat, for example, which is used to warm buildings or generate high temperature steam to produce electricity, results from combustion of fossil fuels. The main point to be made here is that any energy resource, when used to produce useful work, will invariably impact the physical and biological environment. The task of energy planning, as is the goal of energy policies, is to determine the most rational mix of energy resources that have the least impact on the environment and are the most economical for a given region. The United States has a highly decentralized energy system, mostly owned and operated by the private sector. The coal, oil, gas, and nuclear industries are dominated by large private corporations, regulated by various local, state, and federal agencies.