Valorization of slaughterhouse wastes through transesterification for sustainable biodiesel production using potassium hydroxide as a heterogeneous catalyst

Abstract

In this research, biodiesel was synthesized from chicken gizzard using potassium hydroxide catalyst and the effects of operating parameters including catalyst weight percentage (0.005–0.015%), methanol to oil molar ratio (3:1 to 9:1), temperature (50–70 °C), contact time (4–6 h), and stirring rate (400–600 rpm) on the methyl ester conversion yield were investigated. This study is innovative as it explores the transesterification of chicken gizzard, a low-cost feedstock, which has not yet been investigated. Furthermore, the applied catalyst was characterized through BET, FTIR, FSEM, XRD, XRF, EDS/Map techniques, while GC analysis showed that heptanoeic acid (41.57%), arachidic acid (27.63%), and linoleic acid (15.48%) constituted the main constituents of the extracted oil. Based on BET analysis the specific surface area of the used catalyst was 358 m2 g−1 which is an appropriate value for the current purpose. The results revealed that the maximum biodiesel conversion yield (94%) was obtained under the optimal conditions of catalyst weight percentage at %0.01, methanol to oil ratio at a ratio of 6:1, temperature at 60 °C, reaction duration of 5 h, and stirring rate at 500 rpm. The regeneration studies demonstrated that the used catalyst can be used for 2 consecutive cycles with acceptable conversion yields. However, beyond this point, the yield deteriorates, dropping to below 90%. Furthermore, the comparison of the physical characteristics of the generated biodiesel, including density, viscosity, flame point, cloud point, pour point, aniline point, cetane number, and copper strip corrosion with ASTM-D675110 and EN-14214 standards showed that they were within the standards ranges which indicates that the produced biodiesel was a viable alternative to traditional diesel fuel. Considering the promising results obtained from biodiesel production utilizing chicken gizzard for the first time, this waste material can be deemed a cost-effective raw material for biodiesel production.