Comparative study of one-step and two-step slow pyrolysis of bamboo in inert and oxidative media

Abstract

Global energy demand continues to rely heavily on conventional fossil fuels, despite growing environmental and sustainability concerns. Renewable alternatives, such as biomass, have emerged as a promising solution due to their abundance, carbon neutrality, and potential for energy and value-added product generation. Biomass encompasses organic materials derived from plant and animal residues, which can be converted into energy and chemicals through various thermochemical processes. Among these, pyrolysis, a thermal decomposition process conducted in the absence (or limited presence) of oxygen has gained significant attention for its ability to transform biomass into biochar, pyroligneous acid (wood vinegar), and syngas, each with distinct industrial and environmental applications [1], [2]. Slow pyrolysis, characterized by moderate temperatures (300–500°C) and prolonged residence times, favors biochar production, while fast and flash pyrolysis maximize liquid and gaseous outputs [3]. Recent studies have explored stepwise pyrolysis as a means to enhance product selectivity by employing intermediate isothermal stages. For instance, two-step slow pyrolysis has been shown to marginally alter yields compared to continuous methods [4], while combining slow and fast pyrolysis stages increased char yield in eucalyptus wood [5]. Further, stepwise collection of wood vinegar would yield two distinct fractions: one enriched with oxygenated compounds and the other with aromatic compounds, enhancing the versatility of its applications. Despite these advances, low temperature stepwise pyrolysis remains underexplored, particularly for specific feedstocks like bamboo.