Lignocellulosic and chitin-rich agroindustrial residues as biochar precursors: a screening study based on proximate analysis and analytical pyrolysis

Introduction The thermochemical recovery of non-conventional waste requires selection criteria that go beyond its generic classification as biomass, given the combined influence of moisture, mineral fraction, and biopolymer composition on vapor and condensate formation. This study evaluated the suitability of five types of waste for different thermal conversion pathways. Methods The physicochemical properties of the selected materials were determined using proximate analysis, while the semi-quantitative composition of the volatile products was characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results The materials did not constitute a homogeneous category but were grouped into three main behavioral patterns: wet lignocellulosic wastes requiring pretreatment, herbaceous matrices with high mineral content and marked ash interference, and nitrogenous marine wastes with a distinct chemotype. G. ulmifolia showed the greatest operational compatibility for standard pyrolysis due to its low moisture content and profile dominated by carbohydrate-derived products. T. cacao and B. beyrichiana generated condensates rich in oxygenated compounds, particularly cyclopentenones, lactones, and guaiacol, supporting their potential use as sources of platform molecules or for selective fractionation. A. truxillensis produced the volatile fraction richest in hydrocarbons, including BTEX, although its high ash content requires mineral control to maximize liquid yield. L. vannamei exhibited the most distinctive profile, characterized by phenols, nitrogen-containing heterocycles, and levoglucosenone-type carbonyls, compatible with a chitin biorefinery scheme. Discussion Combined screening using proximate analysis and Py-GC/MS enables the differentiation of waste materials according to their thermochemical behavior, facilitates the identification of realistic value-added pathways, and provides a basis for subsequent bench-scale and catalytic design studies.