Abstract
Physicochemical properties of biochar, which are used as a soil amendment material in agricultural fields, are different depending on biomass feedstock and pyrolysis processes. In this study, we evaluated the influence of feedstock type and pyrolysis temperature on the water-retention related properties of biochar. Wood-chips [cedar (CE) and cypress (CY)]; moso bamboo (MB); rice husk (RH); sugarcane bagasse (SB); poultry manure (PM) and agricultural wastewater sludge (WS) were each pyrolysed at 400, 600 and 800 °C with a retention time of two hours. Scanning electron microscopy micrographs (SEM), hydrophobicity indices, pore-size distribution measured by mercury-intrusion porosimetry, water-retention curves (WRCs) and plant-available water capacities (AWCs) of the biochars were measured to evaluate their potentials as soil-amendment materials for improving soils’ water-retention. As the pyrolysis temperature was increased, the hydrophobicity index decreased. On the other hand, pyrolysis temperature did not affect the distribution of micrometre-range pores, which are useful for plant-available water, of biochars. The AWCs of the biochars formed from CE, CY and SB were greater than those produced from other feedstocks, at 600 and 800 °C. Therefore, we can suggest that the biochars derived from wood-chips (CE and CY) and SB have greater potential for enhancing soils’ water-retention.
Highlights
Biochar is the solid product obtained from thermochemical conversion of biomass in an oxygen-limited environment [1]
The biochar yields were influenced by the feedstock and pyrolysis temperature
(22–41%, 23–39%, 25–39% and 19–28%, respectively) from the CE, CY, moso bamboo (MB), and sugarcane bagasse (SB)-derived biochars, which may have been due to the higher ash content of Rice husk (RH), Poultry manure (PM), and wastewater sludge (WS) [23]
Summary
Biochar is the solid product obtained from thermochemical conversion of biomass in an oxygen-limited environment [1]. When biochar is used as a soil-amendment material, it can affect the soil’s physical properties such as texture, porosity and pore-size distribution (PSD) because of its highly porous structure [2]. These changes influence plant growth because the availability of water within the root zone is primarily determined by the physical properties of the soil around the roots. Improving soils’ water-retention with biochar is partially dependent on the physical and chemical properties of the biochar, which are determined by the type of feedstock and pyrolysis processes used to produce the biochar and the amount of biochar added to the soil [4]. Certain feedstocks may be selected and the pyrolysis conditions may be tailored to produce biochars that maximise soils’
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