Properties of Biochars Prepared from Local Biomass in the Mekong Delta, Vietnam

Loc Xuan Nguyen, Phuong Thi My Do, Chiem Huu Nguyen, Royta Kose, Takayuki Okayama, Thoa Ngoc Pham, Phuong Dat Nguyen, Takayuki Miyanishi

Abstract


Wood- (bamboo and melaleuca) and herbaceous-based (rice husk and water hyacinth) biochars, produced from local biomass by slow pyrolysis at 500 °C, 700 °C, and 900 °C, were examined for their physical and chemical properties. The wood-based biomass produced biochars with lower ash contents (<14 wt.%db ash) and higher fixed carbon contents (> 54 wt.%db), greater higher heating value (>23 MJ/kg), higher degree of aromaticity (with O/C, H/C, and volatile matter/fixed carbon ratios were less than 0.08, 0.51, and 0.61, respectively), and smaller amount of salt nutrients (<76 g/kgdb) compared with those of the herbaceous-based biochars. Their unique properties have generated more interest in using them as a solid fuel, for carbon sequestration, and for soil amendment. The rice husk biochars contained more than 300 g/kgdb silica, which is potential for silicophilic plants. The water hyacinth biochars with the greatest volatile matter/fixed carbon (ranging from 0.72 to 2.35), and highest O/C ratios (0.11 to 0.18), indicating the lowest aromaticity among studied biochars and thus maybe least suitability for carbon sequestration. They also possessed a highest soluble salts content (>240 g/kgdb), highest electrical conductivity (>6489 S/cm), and greatest liming potential (>6.56 %CaCO3–eq), which may not be suitable for salt-sensitive plants or low-buffer capacity soils.

Keywords


Biochar; Physicochemical properties; Bamboo; Melaleuca; Rice husk; Water hyacinth

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