Coal is a combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds or coal seams.
Evolution dates back to pre-historic times – to approximately 325 million years ago when the region was covered in lush, dense vegetation.
Coal beds consist of altered plant remains. When forested swamps died, they sank below the water and began the process of coal formation. However, more than a heavy growth of vegetation is needed for the formation of coal. The debris must be buried, compressed and protected from erosion. Even though all the biological, geographic and climatic factors may be favourable, coal could not be formed unless the plant debris was submerged and buried by sediments.
Coal liquefaction is one of the backstop technologies that could potentially limit escalation of oil prices and mitigate the effects of transportation energy shortage that will occur under peak oil. This is contingent on liquefaction production capacity becoming large enough to satiate the very large and growing demand for petroleum.