Characterization and thermal analysis of agave bagasse and malt spent grain

Abstract

A comprehensive study on agave bagasse (AB) and malt spent grains (MSG) was performed using thermal analysis (TG-DTA) to characterize their thermal behavior. The study also focused on to identify their constituents by the application of elemental, proximate, and chemical analyses. The calorific values were also tested. The Fourier transform infrared spectroscopy (FTIR) was used to determine the main constituents. SEM images showed that their morphology and X-ray diffraction patterns of these residues showed their characteristic structures. Thermal degradation of AB and MSG presented two mass loss steps: the first step can be attributed to the release of moisture, and the second one is related to the release of organic volatile compounds. Based on the chemical analyses, the determined quantity of volatile materials, ash, and fixed carbon for AB were 78.1, 7.4, and 14.5 %, respectively; whereas for MSG were 79.9, 6.3, and 13.8 %, respectively. Additionally, MSG had hemicelluloses in a higher extend compared to AB, but the former had a greater content of cellulose than MSG. The calorific value for AB and MSG achieved 16.35 and 19.06 kJ g⁻¹, respectively. The FTIR analysis showed characteristic bands of alkenes, esters, aromatics, ketones, and alcohols. EDS analyses for AB showed Ca, Cu, and Zn while for MSG metals such as Ca, Si, Cu, and Zn were found. X-ray diffraction patterns of these residues showed mostly cellulose, a common structure present in plants. This research helps to know the properties of these materials and to evaluate them as an energy source.