HRJ4 was cultivated to the logarithmic phase in LB medium, then centrifuged the bacterium suspension at the rotating speed of 5000 r/min. The supernatant was discarded and cells were suspended in sterilized normal saline water. This process was repeated for two or three times. The biochar/wood chips and HRJ4 cell suspension were mixed in 5:100 (W/V) ratios for 12 hr in a shaker at the speed of 150 r/min in order to absorb the bacterium sufficiently to biochar. The mixture was placed in refrigerator at 4°C for further use.