Characterization of Steam Gasification Biochars from Lignocellulosic Agrowaste Towards Soil Applications

Abstract

The main objective of this work was to analyze the physico-chemicals properties of biochars produced from the steam gasification of different lignocellulosic agrowastes, and determine the suitability of these materials to be used in soil amendment and remediation applications. Steam gasification biochars from three lignocellulosic agrowastes were extensively characterized. Coconut shells (CS), bamboo guadua (BG), and oil palm shells (OPS) were chosen as raw materials, considering their different macromolecular structure and inorganic composition. The biochars composition, morphology, pH, acid neutralization (ANC) and cation exchange (CEC) capacities, as well as their mineral release at different conditions were evaluated and compared. The experimental results showed that the inorganic content and composition of the biochars have a stronger impact on their properties for soil applications, in comparison to their organic composition and morphology. In particular, BG biochar, the sample with the highest mineral content, exhibited the most notable cation exchange (45 cmolc/kg) and acid neutralization capacities (125 cmol H+/kg), together with the greatest release of plant micro and macro-nutrients. In the case of biochars with low mineral content, higher CEC and ANC were most related to the presence of oxygen-containing functional groups in their surface. Considering that agricultural residues come from numerous sources and activities, the presented results usefully contribute to the comprehension of the relationship between the raw biomass characteristics, the physico-chemical properties of steam gasification biochars, and their expected performance in soil applications, opening a new promising valorization pathway for these materials.