Electron Microscopy Characterization of Stubble Residues (Zea mays) as a Solid Biofuel

Biomass is a renewable and sustainable fuel that can generate a significant reduction in greenhouse gas (GHG) emissions compared to fossil fuels [1]. At present, the use of biomass has increased, particularly that derived from agricultural residues, for the generation of bioenergy, which can be converted into a biomass that can satisfy thermal energy needs through solid biofuels [2]. The use of these transformed agricultural residues as second-generation biofuels could combat the immoderate felling of the forest whose resources are used as fuel in different rural areas of the country [3]. In this sense, the present investigation shows a study on the energy use of corn residues, “stubble” (Zea mays Residue), a residue that was generated after the harvesting of corn in its first stage, and that subsequently accumulates. outdoors and if it is not used as fodder for animal consumption, it burns in the open (Figure 1a), therefore, this available resource may have energy potential and possible application to meet energy needs locally in indigenous communities of Mexico. To carry out the research, Zea mays residues were collected on the land of different farmers located in the indigenous community of San Francisco Pichátaro, Michoacán, México (19.5728900, -101.8073700). The morphology of the collected residues was analyzed by means of scanning electron microscopy (SEM) images, using a field emission Bruker Model Jeol JSM 7600F equipment; A semiquantitative chemical analysis by energy dispersive X-ray spectroscopy (EDS) was also performed. For the calculation of the calorific value (HHV) it was carried out using a mathematical model reported in investigations for lignocellulosic materials [5]. The calorific value could be obtained based on the semi-quantitative chemical analyzes (EDS) and the prediction models based on elemental analysis and on reference data such as HHV = 0.335C (Carbon) + 1.423H (Hydrogen) – 0.154° (oxygen) – 0.145N (Nitrogen); as well as the approximate analysis HHV = 0.3543FC (Fixed Carbon) + 0.1708VM (Volatile Matter); and to the ash content HHV = 19.914–0.2324A (Ashes), data that have been previously reported [4]. Figure 1 (b) and (c) show the waste generation process from stubble collection and material extraction for subsequent analysis and the accumulation of Zea mays residues in the field of the study community. The micrometric morphology of the laminar and agglomerate type of Zea mays residues can be seen in Figure 1 (d), (e) and (f). In addition, the compounds present in the functional groups and the polymeric and glucose compounds are appreciated in semiquantitative chemistry, identifying elements such as Carbon (C) and Oxygen (O), mainly (Figure 1g). Likewise, more than 90% of the weight of the material is attributed to compounds formed by Carbon and Oxygen that, being an organic material with lignocellulosic characteristics, correspond to polymeric compounds where cellulose, hemicellulose, and lignin can be found. The average resulting calorific value was 17.4 MJ/kg, similar to other lignocellulosic residues used in combustion to meet local energy needs [6]. The use of this residue can be used for the generation of solid biofuels, due to the availability of the residue locally and affordably, in addition to its energetic and chemical characteristics that make it a highly efficient material at the time of its densification to manufacture biofuels. solid. The SEM characterization carried out, allowed to know the morphology of the Zea mays residues and to infer the presence of polymeric compounds that are usually present in lignocellulosic materials, which contribute to the calorific value of the material. Therefore, these residues have the potential for bioenergy use to meet local energy demand in a sustainable manner. Zea mays waste generation process: (a) Burning in the open (b) cultivation (c) accumulation of waste and taking samples for analysis. SEM: (d), (e) morphology (f) (g) semiquantitative chemical analysis (SEM-EDS).