Charcoal is a carbon-rich fuel produced predominantly from pyrolysis of wood. In this study, a natural draft-improved charcoal retort system was developed, and the produced charcoal has been analyzed and characterized. The optimal pyrolysis temperature of the retort was established to be 500 degrees C. At this temperature, the mass yield of charcoal was about 29.6 wt %. The energy yield was about 51.8% of the initial energy contained in the biomass. The fixed carbon content was about 78.1%. The charcoal heating value was about 30.8 MJ/kg. The charcoal produced from Prosopis juliflora can be used as a fuel for industrial heat production and in domestic cooking in rural areas. The retort system operates in an environmentally friendly way with very low emissions of CO, CO2, hydrocarbons, and particulate matter.