Improved yield and higher heating value of biochar from oil palm biomass at low retention time under self-sustained carbonization

Oil palm biochar with high yield and higher heating value under low energy requirement is required for improved waste management and utilization in the palm oil industry. This paper presents, a self-sustained carbonization of oil palm empty fruit bunch biomass, without internal heating element, which produced high biochar yield and higher heating value. Three different particle sizes of pressed-shredded oil palm empty fruit bunch biomass, i.e. below 29 mm, 30–99 mm and 100–150 mm, at 8–10% moisture content were used. The carbonization temperature was monitored and used as an indicator to stop the carbonization prior to harvesting. The maximum carbonization temperature recorded was 600 °C. In our previous report, harvested at 300 °C under uncontrolled exhausted air flow rate and found that the higher heating values obtained were 23.0–25.0 MJ/kg. However the biochar yield was only 14–16 %. In order to increase the yield of biochar, the exhaust air flow rate has been fixed at 36 m3/hr by using an air suction blower to ensure uniform circulation and distribution of hot air from top to bottom before being discharged. The biochar was harvested when the temperature of the bed decreased to 500 °C. The particle size range from 100 to 150 mm produced the highest biochar yield of 26.0 ± 1.2% with higher heating value of 23.0–23.5 MJ/kg within 5–8 h retention time. The gaseous emissions were lower than permitted level set by the environmental authorities. The technology developed in this study should be used to improve the management and utilization of oil palm biomass towards a more sustainable palm oil industry.