Sustainable methods to transform eggshells and vaccine wastes into value-added by-products

Abstract

Today the world population is already consuming more natural resources than the planet Earth can sustainably regenerate itself. Nonrenewable resources such as rocks have been used to synthesize fertilizers to increase crop productivity and ensure food security. These rocks are also used in the synthesis of analytical-grade chemicals to clean wastewaters. The partial substitution of rocks by solid wastes generated in industrial processes is a sustainable and innovative way to recycle these materials and minimize the use of nonrenewable resources. This work presents straightforward methodologies to transform solid waste generates from egg companies and vaccine industries into byproducts that can partially replace analytical grade compounds and commercial fertilizers. First, we proposed the transformation of eggshells into a white solid named as “Hydroxyl-Eggshell” (ES-OH). Batch experiments proved that ES-OH has a high potential for arsenic (As) and phosphorus (P) removal. The maximum As and P removal capacity of ES-OH was 529 and 329 mg g-1, respectively. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and X-ray diffraction (XRD) were used to characterize the material before and after As and P reaction. FTIR, SEM-EDS, and XRD confirmed that the primary process of P recovered by ES-OH was via precipitation of hydroxyapatite, while As removal happened by the precipitation of vladimirite crystals. Also, a pot experiment confirmed that the P-loaded ES-OH was as effective as triple superphosphate (TSP, a commercial fertilizer) on grass yield with the advantage of maintaining nearly four-fold more available P and higher soil pH than TSP after cultivation. For the vaccine industries waste (VW), we proposed this material’s chemical and thermal transformation into an organomineral fertilizer. The process proposed here enables the sterilization of this biologically contaminated waste and allows for the production of a green fertilizer with higher phosphorus content and smaller acidity than conventional commercial fertilizers. The methods described in this thesis are ready to be implemented on an industrial scale. Besides being a novel and economical income source, egg-producing companies and vaccine industries might implement the proposed production processes as a local environmentally-friendly way of recycling their solid wastes, creating byproducts with great potential to be used in agriculture as an alternative fertilizer or in wastewaters treatment plants.