Identification of Nodes and Internodes of Chopped Biomass Stems by Image Analysis using Profile Curvature and Slope

Abstract. Morphological components of biomass stems vary in their chemical composition and they can be better utilized when processed after segregation. Even among the stem, nodes and internodes have significantly different compositions. The internodes having low ash content is a better feedstock for bioenergy and biofuel application than the nodes. With chopped stems, nodes and internodes are difficult to segregate by simpler mechanical means, even though they are clearly different in visual appearance. Digital image analysis can be used to extract the total profile of chopped stems laid out as a single layer. Analysis of the profile identifies the presence or absence of the bumps, hence the identification of nodes and internodes. Two algorithms, namely (1) Fourier analysis based curvature, and (2) analytical geometry based slope were developed in MATLAB environment and tested with chopped stems of big bluestem. Digital images of the samples were obtained using a digital scanner at 600 DPI resolution. Both algorithms transformed the object profile into curves of curvature or slopes that resulted in peaks indicating the presence of corners (major peaks) and nodular ring bumps (minor peaks). Presence of two or more peaks indicated nodes and otherwise internodes. Both methods successfully identified the nodes and internodes without any misclassification and produced similar results; however, the geometric slope method is direct, simpler, and might results in faster computation.