ORGANIC PETROGRAPHIC AND GEOCHEMICAL CHARACTERISTICS OF LAFIA-OBI COAL MIDDLE BENUE TROUGH BASIN, NIGERIA

Coal is presently the most available fossil fuel resource in the world and can be seen as a necessary part of the world's energy resources for the future as well (Kettanah and Eble, 2017). Power generation from coal can, with proper exploitation, resolve several problems regarding energy diversification and self-sufficiency of developing nations. Coal is the main source of energy and has been an important part of the world's energy mix; it currently contributes 38% to global electricity generation according to Khan et al. (2018). Coal has contributed to the socio-economic growth and sustainable development of many countries worldwide, as observed by Kettanah and Eble, (2017), despite growing concerns over environmental degradation, global warming, and climate change reported by McGlade and Ekins (2015) and Meinshausen et al. (2009). According to the United States Energy Information Administration, the estimated world's total coal reserves stand at 926 Gt or billion tonnes with significant deposits located in China, USA, India, Australia, Indonesia, Russia, and Germany (IEA-OECD, 2002; Speight, 2012). Coal is classified into three major types namely anthracite, bituminous, and lignite. However there is no clear demarcation between them and coal is also further classified as semi- anthracite, semi-bituminous, and sub-bituminous. Anthracite is the oldest coal from geological perspective. It is a hard coal composed mainly of carbon with little volatile content and practically no moisture. Lignite is the youngest coal from geological perspective. It is a soft coal composed mainly of volatile matter and moisture content with low fixed carbon. Fixed carbon refers to carbon in its free state, not combined with other elements. Volatile matter refers to those combustible constituents of coal that vaporize when coal is heated. Dehydration is the most common reaction in the conversion of wood, cellulose, lignin, and peat to lignite. In the conversion of lignite to bituminous coal, decarboxylation is the most important reaction and demethanation reaction converts bituminous to anthracite coal (Takanohashi, 2016). Coal, as a sedimentary rock, is a complex mixture of organic and inorganic matter, containing intimately mixed solid, liquid and gaseous phrase which have allothigenic and authigenicorigins (Liu, 2006). Every deposit of coal has its plant constituents, regional deposition and paleo-environmental factors; the latter are responsible for specifying the predictable end products that develop for a definite set of conditions in the biological, chemical and physical environment where minerals can be formed. Hence, the final chemical and mineral composition of a given coal is a very important unique genetic code, indicating the changes at different stages during material deposition and coalfication (Liu, 2006). The mineral matter present in coal affects different aspects of coal mining and preparation. This inorganic constituent is responsible for various industrial, technological and environmental problems related to coal use (Liu, 2006). Coals generally contain 10-30% of inorganic material made up of clay minerals, quartz silt, and sand, thus contributing to metal emission load upon their combustion, (Saikia et al. 2009; Singh et al. 2015a; Dai et al. 2016). By igniting coal, the Sun energy stored in it is being released, thus producing heat and energy needed for industry, and generally, sustaining nations' standards of living. However, the fuel burning emissions are the largest source of anthropogenic greenhouse gases and aerosols (Kumar et al., 2017a).