Combustion profiles: A means to characterize the Cretaceous-Cenozoic coals in the Benue Trough, Nigeria: An insight for Electricity Power Generation.

Abstract

This study presents an integrated geochemical, petrographic, and thermogravimetric 
assessment of Cretaceous–Cenozoic coal deposits from the Benue Trough, Nigeria, with 
the objective of characterizing their combustion behavior and evaluating their suitability 
for thermal power generation. The Benue Trough is a major NE–SW trending 
intracontinental rift basin extending from the Gulf of Guinea to the Chad Basin and hosts 
significant coal-bearing successions of economic importance. Despite the global 
transition toward low-carbon energy systems, coal remains a strategic component of the 
global energy mix, particularly in developing economies where energy demand continues 
to increase and infrastructure for renewables remains limited. Twenty-nine 
representative coal samples collected from multiple sub-basins within the trough were 
subjected to proximate analysis, total sulfur determination, bomb calorimetry, 
reflected-light petrography (maceral quantification), and thermogravimetric analysis 
(TGA). Proximate data indicate generally high volatile matter contents and low ash yields, 
consistent with sub-bituminous to high-volatile bituminous rank. The average gross 
calorific value is 24.82 MJ/kg, suggesting moderate-to-high energy potential. Total 
sulfur contents are generally low to moderate, supporting their potential for relatively 
cleaner combustion compared to high-sulfur coals. Petrographic examination reveals that 
the organic fraction is dominated by vitrinite (mean 59.3 vol.% on a mineral-matter-free 
basis), indicating significant contribution from woody precursor material deposited 
under predominantly reducing conditions. Inertinite contents show marked variability 
across the Upper, Middle, and Lower Benue sub-regions, reflecting spatial differences 
in paleofire intensity, oxidation conditions, and depositional regimes. Liptinite macerals 
are sparse and notably absent in samples from the Middle Benue Trough, suggesting 
limited preservation of hydrogen-rich algal or resinous components. Thermogravimetric 
profiles demonstrate characteristic devolatilization and combustion stages consistent 
with vitrinite-rich coals. Except for samples 01 and 17, which exhibit anomalously high 
ash yields (73.03 wt.% and 81.57 wt.%, respectively) and are thus unsuitable for efficient 
combustion, the majority of the samples meet fundamental criteria for coal-fired power 
applications. Overall, the results establish that most Benue Trough coals possess 
favorable combustion characteristics and calorific properties, supporting their strategic 
potential for domestic power generation and energy security in Nigeria.