## 1 Introduction  
To address various UN Sustainable Development Goals (UN SDGs 12.5, which targets substantial reduction of waste generation) [1], there is a need to convert generated waste materials into value-added products. Strategies to achieve the UN SDGs include recycling, reusing, or re-channeling waste with concerted efforts to manufacture higher-value products [2]. Over the years, research on eggshell waste has aimed at its greater utilization in a bid to repurpose agriculture waste, such as a soil amendment material to increase the pH and fertility of soil, by high-temperature calcination of eggshells to obtain calcium oxide, CaO [3]. Generally, there are sparse studies on the use of eggshell wastes to cover a range of applications, such as cosmetics [4], cement production [5], polymer and metal composite production [6], as a fertilizer additive, and as a feed supplement for livestock. Furthermore, because of the highly porous nature, estimates indicate that each eggshell contains between 1700 and 7000 pores [7]. In turn, eggshells (ESs) were studied as potential adsorbents for the treatment of contaminated soils and wastewater [8, 9]. There is an increasing awareness that the generation of eggshell (ES) waste is rapidly skyrocketing because eggs or its food products are consumed that add to the burgeoningquantity of food waste produced daily, since eggsshells are typically landfilled at the consumer levels. From Figure 1, there is a representation of the global egg production, which shows a steady increase in production over several decades and reflects the magnitude of potential amounts of available ES waste. Based on the known wt. content of eggshells, the amount of ES waste in 2019 was estimated as 8.21 M metric tons (equivalent to the weight of 4.1 M passenger cars, based on 10 wt.% for typical chicken eggs). The increasing annual consumption of eggs and disposal of ES waste highlights the need to provide alternative strategies for waste utilization and valorization. Proper management of solid waste is an issue of great environmental concern as the world is currently witnessing high waste generation due to population rise, economic growth, and rapid urbanization. It is estimated that the global urban waste production in 2025 and 2050 will reach 2.2 billion tons and 4.2 billion tons, respectively [10]. Limited availability of resources for environmentally friendly solid waste treatment methods have made solid waste treatment a global challenge [11]. Solid waste treatment technologies can be divided into two broad classes: conventional and non-conventional treatments. The conventional approaches include anaerobic digestion, composing, landfilling, and incineration, while non-conventional approaches include technologies such as pyrolysis, gasification, hydrothermal incineration, liquefaction, etc. [12; 13], where such methods reduced the mass (70%) and volume (90%) of the waste to be disposed. Aside from the cost of managing these various technologies and their inherent limitations, the solid waste is generally not targeted for re-use. Valorization of waste is a term used to explain the concept of waste disposal and adding value by converting waste to energy or useful materials. This approach is adopted for preservation of the environment and its natural resources. Valorization of waste may involve biochemical and/thermo-chemical processes. Electricity, heat generation, road construction materials, and soil fertilizers are some examples that highlight the valorization of solid waste. To improve the sustainability of biogenic ES waste, research on the use of this resource represents a potential opportunity to divert ESs from landfill disposal via recycling and valorization. This includes composite materials that contain ESs, which have potential utility as adsorbent materials for wastewater treatment [14]. Research into the alternative use of ESs as composites was borne from its current supply and availability, along with the projected increase in its consumption, relative abundance, and low cost of ES.