Umudike Journal of Engineering and Technology

The global energy sector is under increasing pressure to reduce emissions from coal-fired power plants. A way to transition from fossil fuels to renewable energy using existing infrastructure is to co-fire with biomass pellets. This study evaluated the emission and energy characteristics of sub-bituminous coal–coconut shell pellets bound with waste paper using ultimate analysis and stoichiometric combustion calculations. Coal from Enugu was blended with coconut shell at ratios of 100:0, 90:10, 80:20, 70:30, 60:40 and 50:50 (coal: coconut shell) and pelletised with a waste-paper binder. Six samples were characterised for ash content, calorific value, elemental composition (C, H, N, S, O) and theoretical wet- and dry-basis emissions of CO₂ and SO₂. Results showed that calorific value decreased progressively with increasing coconut-shell content from 19.78 MJ/kg (100 % coal) to 15.70 MJ/kg (50 % coal–50 % coconut shell). Ash content declined from 18.5 % to 10.9 %, while sulphur and nitrogen contents also decreased. Both wet- and dry-basis SO₂ emissions fell with higher biomass proportion; wet-basis CO₂ remained relatively stable. Blends containing 20–40% coconut shell provided the optimal trade-off between energy density and emissions reduction. The pellets, produced from agricultural and paper wastes, constitute a cleaner co-firing alternative that can partially displace coal in industrial boilers and power plants. It is recommended that pilot-scale combustion trials be conducted on the 20–40 % blends to confirm operational performance before full-scale adoption.