# Vermicomposting: A Valorization Alternative for Corn Cob Waste
## 1 Introduction  
Worldwide corn production is estimated to be 1133.9 million tons for the 2020/2021 cycle [1]; making it the most produced grain, and second most produced crop. The American continent produces nearly 55% of the world's total production, followed by Asia, Europe, and Oceania. Its uses include human food, animal feed and feedstock for a large quantity of industrial products as well as biotuels [2]. The industries in which corn-based products are applied include the automotive, pharmaceutical, cosmetic as well as the clothing and footwear industries, where it is a source of furfural for the manufacture of nylon and phenol-formaldehyde plastics, the fabrication of petroleum-based lubricants and a purifier of butadiene in the production of synthetic rubber, an ingredient in the production of organic marine algae fertilizers, among others [3]. In corn cultivation, 50% of the yield is harvested as grain and the remaining 50% is made up of residues such as stalks, leaves, husks, and panicles, among others. This waste is used in the process of obtaining fiber for animal feeding and ethanol production or for ground cover [4]. Its use has also been reported to produce furfural and production of paper pulp [5]. Agroindustrial untreated waste such as corn cob waste is, on the whole, not properly disposed of (common methods being burning, dumping or unplanned landfilling), whichcauses environmental pollution, resulting in an increase in greenhouse gases and climate change [6]. Another waste management alternative is its treatment through biological processes, the most reputable being anaerobic digestion and composting. One of the modalities of the latter is vermicomposting, a rapid, simple, and easy-to-control energy-saving method, which allows the bioconversion of organic waste through a non-thermophilic process that generates a quality product known as vermicompost [7; 8; 9]. Due to the environmental issues generated by the produced residue, this process has become an emerging treatment option that is effective for a large array of industries with a greater potential for nutrient recovery [10]. Vermicomposting studies have shown favorable results for obtaining soil improver [11]. [PERSON] et al. performed an experiment with maize stover and chicken droppings as a substrate using _Amynthas hupeiensis_ worms and a pre-composting phase spanning 15 days, concluding that earthworms could accelerate maize stover stabilization by activating lignocellulosic-degrading microbes [12]. [PERSON] et al., in a similar experiment, used maize stover mixed with chicken droppings, applying a prior pre-composting process of the substrate for 15 days to prevent any damage to the worms when temperatures went above 35 \({}^{\circ}\)C [13]. The species of worm used was _Eisenia fetida_ and during the process, temperature was kept around 25 \({}^{\circ}\)C, while humidity was in the 55-65% range during the 60 days in which the experiment lasted. In another experiment performed by [PERSON] and [PERSON], in which phase one, the pre-composting of wheat straw during a 4-day period, was inoculated with four different funguses, the results showed the production of a nutrient-enriched compost product [14]. [PERSON] performed a vermicomposting experiment using three different mixtures of millet straw and sheep manure, pulse bran, wheat straw and cow dung, mixed crop residues and cow dung [15]. The results showed that the higher concentrations of nutrients in the final product had the potential for agricultural waste use in sustainable crop production. [PERSON] et al. performed a study to determine the effects of the C/N ratio in mixtures of maize (_Zea mays_ L.) subtle and milk cattle manure on vermicompost quality, finding it to be a good alternative for horicultural and ornamental plant production [16]. In accordance with the aforementioned studies, the vermicomposting process through use of corn waste has been performed by different authors using mixtures including various types of animal manure.