Physico-hydraulic properties of sugarcane bagasse-derived biochar: the role of pyrolysis temperature

Abstract

The study of biochar properties has received increasing attention by the scientific community in recent years. This study aimed to identify the most environmentally-relevant physico-hydraulic characteristics of slow-pyrolysis sugarcane bagasse-derived biochar prepared at temperatures of 300 (BC300), 400 (BC400), 500 (BC500), and 600 °C (BC600) and comparing the properties to those of the sugarcane bagasse (BG). The real density (RD) of biochar samples significantly increased from 1.42 to 1.64 g cm−3 as pyrolysis temperature increased from 300 to 600 °C. BG and BC600 showed the lowest and the highest N2 adsorption, specific surface area, total pore volume, microporosity, and adsorption energy, respectively. The average pore diameter of resultant biochars decreased with increasing pyrolysis temperature. The adsorption behavior of biochars was more like mesoporous materials, and the hysteresis effect increased with raising the pyrolysis temperature. Biochars were hydrophilic and were able to immediately absorb water, while BG showed hydrophobic properties with contact-angle (θ) of 107.6°, ninety-degree surface tension (γ90°) of 35.0 mN m−1 and solid–air surface tension (γs) of 8.7 mN m−1. The pore-size-distribution (PSD) curve based on water adsorption data gives clearly better results about large PSD responsible for water and solute transport than N2 adsorption. Thereby, it seems that high RD biochars may have high residency time and be more suitable for carbon-sequestration purposes. Biochar produced at low temperature (BC300) may improve nutrient-availability and crop productivity in acidic/alkaline soils, whereas high-temperature (BC600) may enhance long-term soil carbon-sequestration. Biochars produced at intermediate temperature (BC400 and MC500) seems be better in improvement of soil hydraulic properties associated with plant growth.