The percentages of carbon, hydrogen, nitrogen, sulfur and oxygen (by difference) of the EFB sample were determined after complete combustion of the sample using a CHNS/O Analyzer (model LECO TruSpec CHN, USA) following the ASTM D-5291 method. Approximately 5.0 mg of grained EFB samples were placed in a tin capsule and the capsule was crimped. This capsule, together with capsules serving as a blank and capsules containing a standard (sulfamethazine) were placed into the autosampler of the CHNS/O analyzer. The analyzer oxidation temperature was set at 1000 °C. Helium, oxygen and nitrogen were used as carrier combustion, autosampler injection gases, respectively.