Characterization of biochar from fast pyrolysis and its effect on chemical properties of the tea garden soil

• Rice husk biochar and elm sawdust biochar were from fast pyrolysis in a fluidized bed reactor, which was different from the conventionally slow pyrolysis.
• The physical and chemical properties of the feedstocks and biochars were analyzed and the relationship between feedstock and biochar was described.
• The characteristics of the two biochars were compared.
• The Fourier Transform Infrared Spectroscopy (FTIR) results revealed that rice husk biochar had more functional groups than elm biochar.
• Incorporation of the rice husk biochar from fast pyrolysis could also significantly improve the soil properties.

The characteristics and application of biochar from conventionally slow pyrolysis have been studied a lot, but biochar, as a byproduct in the bio-oil production process, produced by fast pyrolysis was rarely studied. This work assessed the characterization and utilization of biochars derived from rice husk (RH) and elm sawdust (ES) by fast pyrolysis. Incubation experiment of rice husk biochar (RHB) and acid soil in a controlled cabinet was carried out to test the effect of biochar on soil available elements. The volatile and fixed carbon was 2.2 and 1.7-fold respectively higher in elm sawdust biochar (ESB) than those in RHB, but the ash content was 4.2-fold higher in RHB than that in ESB. Although the C, H, N, and O contents were significantly varied in two biochars, the ratio H/C and O/C were nearly the same. The Fourier Transform Infrared Spectroscopy (FTIR) results revealed that RHB had more functional groups than ESB. More surface area was found in RHB (78.15 m2 g−1) than ESB (0.22 m2 g−1) by BET test. Incorporation of the biochar improved the quality of acid soil properties. The levels of soil pH, K, Ca, Mg, Na and total C and N increased while the Al and Pb contents decreased. Total carbon and potassium increased by 72% and by 6.7-fold respectively over the control at 4% of rice husk biochar adding level.