Abstract. The biochar produced from the agricultural wastes was aimed to amend the extreme degraded soil. The properties of biochar prepared from Acacia wood and coconut shell were investigated by different pyrolysis conditions in order to identify the suitable initial biomass of biochar applied for sandy soil amendment. The slow pyrolysis was applied for preparing biochar under different conditions. The temperature was varied from 300, 400 and 500 o C meanwhile the pyrolysis times were varied to 1, 2 and 3 hours. The parameters indicating biochar property are SA, APD, elemental contents of C, H, O and N, pH, CEC, and WHC. The properties of Acacia biochar and coconut shell biochar were compared using paired T-test at 95% confident interval to analyze the significant difference. The results indicated that the types of the initial biomass and the pyrolysis conditions have an impact on the properties of biochar for both physical and chemical. The suitable temperature was 500 °C for 2 hours. The different types of biomass are significantly effect on the SA, C and O contents, pH, CEC and WHC of the prepared biochar (P<0.05). Properties of Acacia wood biochar indicate that it is more suitable than coconut shell biochar to be applied as sandy soil amendment due to its higher SA, higher CEC, and neutral pH. Meanwhile, coconut shell biochar also can be applied for the typical soil appropriate and increase crop yield.

This paper reports studies to investigate the relationships between hydrophobicity of biochar surface and soil water retention. The studied biochars were produced from acacia wood, cashew wood and bamboo. The resulting materials were oxidized via liquid oxidation to generate hydrophilic biochars containing oxygenated functional groups on the surface. All biochars were characterized and their ability as soil additives to enhance water retention was assessed. Our results suggest that hydrophobicity/hydrophilicity of biochars is not the major factor governing water retention ability of this particular soil. However, hydrophilicity of biochar helps improve soil permeability by providing better wettability to the soil.

Biochar was prepared from Acacia wood by slow pyrolysis process under different conditions in order to determine the optimum condition of the pyrolysis temperature and time. The temperature was varied from 300-500 O C meanwhile the time was varied from 1-3 hours. The regression analysis was applied to investigate the relationship between surface area, APD, and pH of biochar (response variables) and the independent factors (temperature and time). The response surface methodology was used for determining the optimum condition of biochar preparation from Acacia wood. The relationship between all response variables and the pyrolysis temperature and time is fit to the first order linear regression model. The pyrolysis temperatures have the significant impact (at 95% confident interval) on the surface area and APD of biochar meanwhile the pyrolysis times do not. The optimum condition for preparing biochar from Acacia wood using the laboratory electrical furnace is at 434.8 O C, 1 hour of pyrolysis temperature and time. In addition, the proposed range of the optimum pyrolysis temperature is 413-450 O C and the range of the optimum pyrolysis time is 1-2 hours.