This thesis focuses with an engineering approach on researching the literature and history of underground coal gasification. In specific, critically analysing the relations within the process incorporating tests and trials that have been carried out on a worldwide perspective. The relevance to the area of research is essential due to the renewed interest in utilisation of underground coal seams as an alternative source of improving fossil fuel power generation. Therefore, collating a substantial amount of available information relevant to UCG, such as understanding the history of the process, comparison of tests and trials, methods/procedures used and implemented/adopted over the years is essential. Other issues to be considered include focussing on alternative technology, demands, social, commercial, sustainability and environmental concerns.Knowledge uncovered by this investigation will assist other areas of research by highlighting all the relevant technical and practical issues that have occurred with the technological advancements over the past 100 years. It is essential to facilitate further developments, commercialisation, and the uptake of UCG technology for the power generation and chemical production as a competitive industrial fuel source for future sustainability. The other two major fuel sources that are currently utilised are oil and gas.....