From semi-arid biomass to carbon sequestration: Role of pyrolysis atmosphere and temperature on agave-derived biochar properties

Abstract

Biochar has emerged as a scalable negative emission technology with promising agronomic and environmental benefits. In this context, arid and semi-arid regions represent promising zones for carbon removal through soil biochar application, particularly when exploring new non-food biomass sources with high energy potential, such Agave wercklei. This study aims to evaluate the properties of biochars produced from Agave wercklei and investigate the role of pyrolysis atmosphere by comparing nitrogen (N₂) and recirculated pyrolysis gas (PyGR) across four temperatures (350, 425, 500, and 575 °C). PyGR-based biochars exhibited higher carbon content (up to 71.36 %), energy density, and enriched surface chemistry with increased aliphatic functional groups, retention of dissolved organic carbon, while N₂-based biochars showed greater aromaticity, higher thermal stability, and lower content of volatile compounds. Differences were also observed in handling and interfacial properties, with PyGR-based biochars presenting superior flowability and higher hydrophobicity, while N₂-based biochars exhibited greater water retention. Multivariate analysis revealed that the pyrolysis atmosphere plays a crucial rule in key indicators, including atomic ratios (H/C, O/C), aromatic indices, and thermal degradation profiles. Thus, the use of inert gas in bench-scale studies may thus misrepresent the carbon permanence and agronomic behavior of biochars produced under realistic industrial conditions. Furthermore, Agave wercklei demonstrated favorable biochar properties, positioning it as a valuable biomass for producing biochar in semi-arid regions.