Biocompositional and thermodecompositional analysis of South African agro-waste corncob and husk towards production of biocommodities

Abstract

Biocompositional and thermodecompositional analyses of locally abundant agro-wastes of South African corn were evaluated for their potential utilization as biocommodities via thermochemical and bioconversion processing. Corncob of Zea mays Zama star (white) & PAN 6Q-252 (yellow) hybrid as well as the ear husks of South African sweet corn, Z. mays var. Saccharata were utilized in the beneficiation process. Proximate and elemental analyses were conducted to check for the moisture content, the ash content, the volatile matter, and the elemental composition of the agro-waste samples. In addition, the thermal property of the waste, the surface chemistry and the calorific values were investigated using thermogravimetric analysis, Fourier-transform infrared (FTIR) spectroscopy and bomb calorimetric technique, respectively. Significant amounts of alkali metals (Li, Na, and K) were found in the corn cob samples, and heavy metals such as thorium and uranium were detected in the ear husks, indicating that the biomass might not be suitable for use in thermochemical process. However, a relatively high volatile matter content recorded for the waste samples supports their use in thermochemical process with improved yield per gram of feed. These and other findings such as the high calorific value of the cob samples and the relatively low lignin-to-sugar ratio of the waste confirm previous reports regarding their suitability as feedstocks in thermo-processing and bioprocessing. With the exception of the moisture content in ear husks, the minimal variation in the physicochemical property of the waste samples substantiates their suitability for co-processing without major upsets in process kinetics. Results of other investigations such as the thermodecompositional behavior of the waste samples and the surface chemistry further shed light on the physicochemical property of the locally sourced lignocellulosic biomass waste samples.