Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geological formations beneath the Earth’s surface. Petroleum is also the raw material for many chemical products (petrochemical) like pharmaceuticals, solvents, fertilizers, pesticides, and plastics.
Some petroleum industry operations have been responsible for water pollution, or the contamination of bodies of water, such as lakes, rivers, oceans, aquifers, and groundwater, through by-products of refining and oil spills, or the release of a liquefied petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution.
The combustion of fossil fuels produces greenhouse gases (GHG), a gas in an atmosphere that absorbs and emits radiation with the thermal infrared range, and other air pollutants as by-products. These includes: nitrogen oxide, referring to a binary compound of oxygen and nitrogen, or a mixture of such compounds like nitric oxide (also known as nitrogen monoxide, NO; nitrogen(II) oxide), nitrogen dioxide (NO2; nitrogen(IV) oxide), nitrous oxide (N2O; nitrogen(I) oxide), nitrosylazide (N4O; nitrogen(I) oxide + diatomic nitrogen), nitrate radical (NO3; nitrogen(VI) oxide), dinitrogen trioxide (N2O3; nitrogen(III) oxide), dinitrogen tetroxide (N2O4; nitrogen(IV) oxide), dinitrogen pentoxide (N2O5; nitrogen(V) oxide), and trinitramide (N(NO2)3); sulphur dioxide, the chemical compound with the formula SO2; volatile organic compounds (VOCs), organic chemical that have a high vapor pressure at ordinary, room-temperature conditions; and, heavy metals, member of a loosely-defined subset of elements that exhibit metallic properties.
As petroleum is a non-renewable natural resource, which occur naturally within environments that exist relatively undisturbed by mankind, in a natural form, the industry is faced with an inevitable eventual depletion of the world’s oil supply. The BP Statistical Review of World Energy 2007 listed the reserve/production ratio (RPR or R/P), or the remaining amount of a nonrenewable resource, expressed in years, for proven resources worldwide. The study placed the prospective life span of proven reserves in the Middle East at 79.5 years, Latin America at 41.2 and North America at only 12 years.
The Hubbert peak theory, which posits that for any given geographical area, from an individual oil-producing region to the planet as a whole, the rate of petroleum production tends to follow a bell-shaped curve, introduced the concept of peak oil, the point in time when the maximum rate of petroleum extraction is reached, after which the rate of production enters terminal decline, and questions the sustainability of oil production. It suggests that after a peak in oil production rates, a period of oil depletion, occurring in the second half of the production curve of an oil well, oil field, or the average of total world oil production, will ensue. Since virtually all economic sectors rely heavily on petroleum, peak oil could lead to a partial or complete failure of markets.
According to research by IBISWorld, biofuels (primarily ethanol, but also biodiesel) will continue to supplement petroleum. However, output levels are low, and these fuels will not displace local oil production. More than 90% of the ethanol used in the US is blended with gasoline to produce 10% ethanol mix, lifting the oxygen content of the fuel.