Compositional characteristics and theoretical energy potential of animal droppings from Adamawa region of Cameroon

Animal droppings are a source of severe environmental and health problems if not well managed. The goal of this study is to evaluate the energy potential of animal droppings from the Adamawa region of Cameroon and to predict suitable thermal conversion technologies. Structural, proximate analyses, and higher heating value (HHV) were determined experimentally, while ultimate analysis, higher heating value and flue gases were modeled from structural and proximate analyses. This study reveals that animal droppings are estimated at 3,292 972 tons of dry bone per year with cattle droppings being the most dominant. Their theoretical energy potential ranges from 48GJ/year to 58GJ/year against 46GJ/year for the experimental energy potential of combustion energy. The average absolute errors (AAE) are 4% and 6% for energy potential from ultimate and proximate analyses, respectively. These AAE are negligible and can justify the reliability of theoretical estimation of energy potential from proximate and ultimate analyses. Results also showed that flue gas released does not have a negative impact on the environment as the values are within admissible limits, and the pollutant emissions are below the regulated threshold values. The animal droppings properties studied show that they can be efficiently used in thermal conversion processes such as pyrolysis, gasification, and biogas as well as catalysts in the thermal conversion technologies. This could produce 7.81 × 10⁸ Nm³/year and 7.70 × 10⁵ m³/year, for annual syngas and methane, respectively. Nevertheless, the levels of S and N could be taken into account in the design of a gasification plant to control the emission of NO₂ and SO_x-derived pollutants as their values are more than 0.2% and 0.6%, respectively. These droppings can be used as alternative energy sources as they are highly available and can improve environmental sustainability.