Influence of hedge bamboo moisture content on wood vinegar quality in a direct-heated gasifier-burner-kiln system

Abstract

This study investigates a direct-heated gasifier-burner-kiln system in which high-temperature hot gas is supplied directly to a charcoal kiln adapted from a reused 200 L drum for carbonizing hedge bamboo. The effect of feedstock moisture content was examined using bamboo with three moisture levels (10%, 20%, and 30%). Product yield, quality, and energy performance were evaluated for biochar, wood vinegar, and pyrolysis gas (non-condensable gas). Increasing moisture content significantly prolonged processing time, from 225 min at 12.5 wt% to 365 min at 30.3 wt%. Biochar yield and energy yield decreased slightly, while fixed carbon content increased (83.0-85.2 wt%) and volatile matter declined, with biochar maintaining a high LHV of 31.6–31.9 MJ kg⁻¹. Electrical properties shifted toward higher conductivity, as low-resistivity biochar increased markedly at higher moisture levels. Wood vinegar quality met Thai standards at all conditions (pH 2.6-2.9), supporting 30 wt% as a practical upper moisture limit. However, higher moisture reduced non-condensable gas quality and combustion completeness. Overall, the proposed system demonstrates effective bamboo waste valorization with improved heat utilization and controlled product quality.