Optimization of elephant dung green fuel briquette production using a low-pressure densification technique and its characterizations, and emissions

Elephant dung is densely packed with undigested fiber, complicating disposal. To manage this waste more efficiently, the dung was converted into biofuel briquettes. Four variables in the briquette production were investigated using three levels of optimization techniques, including a response surface and a central composite design with 95 % confidence. The results show that when compressing a 7:3:1 weight ratio of elephant dung, binder, and water at 40 bars, a briquette density of 613 kg/m3 or 9.09 GJ/m3 could be achieved. Although its dimensional stability was consistent and its shatter resistance was acceptable, its water resistance was poor. The briquettes had atomic ratios of 0.15 and 1.17 for H/C and O/C, respectively. It had a high heating value of 17 MJ/kg and could enhance the stove's overall thermal efficiency by 22 %. The emission study demonstrated that the combustion of the briquettes released mainly CO2 (5.49 x 104 ppm), whereas other gases were negligible.