Biochars from various agro-wastes in Vietnam: Insight into the influence of pyrolysis temperatures on characteristics for potential of waste management

Abstract

Vietnam’s thriving agricultural sector generates significant quantities of agro-waste annually, much of which remains underutilized or unmanaged. This creates environmental and economic challenges, including greenhouse gas emissions and soil and water contamination. This study explores the properties of biochars produced from common Vietnamese agricultural by-products—rice husk (RHB), coconut shell (CCB), durian shell (DRB), jackfruit shell (JFB), and coffee husk (CFB)—under various pyrolysis temperatures. Using advanced analytical techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET surface area calculations, and zeta potential measurements, we characterized the biochars’ physical and chemical attributes. The results showed that the biochars possess distinct porous structures, high carbon content (∼99 %), substantial surface areas up to 514.3 m2/g, negative surface charges, and high cation exchange capacity (CEC), with improved properties observed at higher pyrolysis temperatures. Additionally, heavy metal contaminants and polycyclic aromatic hydrocarbons (PAHs) were detected at negligible or undetectable levels, indicating the biochars are environmentally safe. These findings highlight the potential of biochar from Vietnam’s agro-waste as a sustainable soil amendment and contaminant adsorbent, offering an effective solution to agro-waste management while supporting environmental protection.