Reservoirs of oil are found between rocks in the earth, formed from fossilized animals (BBC, n.d.).
Oil is mainly used for transportation purposes. Several environmental issues are associated with the extraction, transportation, and combustion of oil, and include oil spills as well as the release of fine particulates and greenhouse gases (Environmental and Energy Study Institute, 2014)b. As conventional oil reserves are limited in supply and are running out, industries have more recently turned to unconventional sources such as tar sands and oil shale. The extraction of oil from unconventional sources generates a larger amount of greenhouse gas emissions as compared to conventional sources, further contributing to the problem of global warming and climate change.