Chicken eggshell waste is an alternative renewable source for quicklime production. Eggshell waste has received significant attention from researchers due to it being a potential source of bio-CaO, which not only drives the circular economy concept but also supports sustainable development. However, experiments on the production of bio-CaO are normally conducted in a small lab-scale furnace. Furthermore, the eggshell raw material is collected from canteens or households, which is not suitable for economical or industrial production. Therefore, this study investigated the factors affecting the bio-CaO production from hatchery waste via both batch and continuous calcination process in a laboratory-scale rotary kiln for the first time. The eggshells were first separated from the solid hatchery waste. Then, the effect of preparation methods of raw eggshells on the properties of bio-CaO was investigated, including eggshells with and without membrane separation, various particle sizes, and with an increase of the percent raw material filling in the kiln from 5 to 20%. Calcination of the samples was performed in a rotary kiln at 800 °C with a 0.5 RPM rotating speed and a 5° inclination of the kiln. The effects of the calcination process in either an air or N₂ atmosphere on the calcined product were also observed. Instrumental analysis shows that the production yield and purity of bio-CaO were in the range of 49–56 wt% and 97–98%, respectively. The results also indicated that the production yield of bio-CaO decreased to 17.7% with a decrease in the raw material particle size from 3.3 mm to 250 μm. Moreover, the production of bio-CaO with eggshells containing eggshell membrane decreases the purity of calcium oxide by about 0.7–1.0%. In addition, further increasing the filling volume of the kiln from 5 to 20% had only a slight effect on the purity and yield of the product. These results imply that it is not necessary to remove the eggshell membrane from the raw eggshells in order to produce industrial-grade CaO from the raw eggshell. These new findings can likely be used to develop an alternative process design to reduce the manufacturing cost of bio-CaO produced from hatchery waste. Furthermore, this present study reveals that the specifications of the obtained bio-CaO comply with both Thai industrial standards and international food additive standards.

The valorization of eggshell waste as bio-calcium oxide is crucial for pollution prevention and supporting sustainable development. There are several reports on the thermal conversion of eggshell waste to calcium oxide for the partial or complete substitution of natural lime applications. However, this paper reports the thermal decomposition of large amounts of hatchery eggshell waste on an industrial-scale car bottom furnace for the first time. The hatchery eggshell waste was sundried and placed into five stacked trays in the car bottom furnace. The calcination of the eggshell waste was conducted at 900°C for 3 and 4 h under an atmosphere of air. Both the physical and chemical properties of the eggshell samples and the bio-quicklime products were carefully examined by TGA, SEM, XRD, FTIR, and XRF. The results demonstrate that the purity of calcium oxide in the quicklime products increased from 79% to 87% upon increasing the calcination time from 3 to 4 h. However, the color of the calcined eggshell samples at the surface of the pile was white while the color of the product beneath the surface was black or dark gray. The purity of the calcium oxide of both the black and white calcined samples was 76.4% and 91.5%, respectively. These results indicate the limited efficacy of the car bottom furnace for thermal decomposition of the large amount of eggshell waste to calcium oxide. Additionally, the production cost of bio-calcium oxide is approximately twice the cost of industrial grade lime. For further industrial applications, the furnace should contain the mixing equipment for improving the thermal decomposition of the large pile of eggshell waste. Furthermore, the oil burner system may be used in order to reduce fuel costs.

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The global demand for biochar in agricultural and carbon sequestration applications is increasing; nevertheless, biochar production using the 50-liter household biomass gasifier stove (50L-HBGS) in Thailand found major issues that need to be improved. The objective of this study was to study the effects of the airflow in the non-uniform combustion core shape (NCCS) on the biochar production characteristic of the 50L-HBGS. The new design of the NCCS was constructed and studied to replace the existing combustion core shape (ECCS) at Mahasarakham University. The height, air inlet, and air outlet diameters of the NCCS were designed at 45, 24, and 11.4 cm, respectively. The NCCS with 21 holes of the pyrolysis gas outlet, a diameter of 4 mm for each, was integrated into the 50L-HBGS and performed comparative tests to the ECCS using 9 kg of bamboo wood chunks in three consecutive experiments. The airflow and the combustion behavior were studied through the stove temperature profiles, which were recorded every 5 minutes using a digital data logger. The biochar products were studied using the scanning electron microscope (SEM) with the energy dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and the proximate analysis technique. The study indicated that the 50L-HBGS with the NCCS made significantly improved the airflow rates in the combustion core, resulting in better continuous burning during the ignition state than with the ECCS. Moreover, the pyrolysis temperatures were significantly improved, it was provided temperatures during the pyrolysis process reached higher than 500 oC, resulting in the liquid tar being removed and no unburned wood chunks remaining at the end. The characterization result demonstrated that the 50L-HBGS with the NCCS had created biochar within a range of micropore and macrospore sizes and high fixed carbon content, which could be advantageously used for different agricultural and carbon sequestration applications.

This study investigated the effects of calcium oxide (CaO) derived from eggshells on the gelation properties of surimi prepared from giant snakehead (Channa micropeltes). Surimi gels were enriched with CaO at concentrations of 0, 2, 4, 6, 8, and 10 µmol/100 g, and their physicochemical, rheological, and structural characteristics were evaluated. The optimal CaO concentration (6 µmol/100 g) significantly enhanced gel strength by 48.2%, breaking force by 26%, and deformation by 18% compared to the control (p < 0.05). Expressible moisture content decreased from 16.88% to 7.12%, while total sulfhydryl groups were reduced to 5.17 µmol/100 g. Rheological analysis revealed increased storage modulus (G′) and loss modulus (G″), indicating enhanced gel elasticity and viscosity during thermal processing. Scanning electron microscopy (SEM) demonstrated the formation of a compact, uniform gel network with fine pores at the optimal CaO concentration. SDS-PAGE analysis confirmed that CaO promoted transglutaminase (TGase) activity and TGase catalyzes the formation of cross-links between myosin heavy chain (MHC) and disulfide bonds. These results demonstrate the potential of eggshell-derived CaO as a sustainable, cost-effective additive to enhance surimi gel quality.