Reutilization of Real Waste Calcium Carbonate (CaCO3) from the Palm Oil Industry (POI) for Palm Kernel and Shell Separation Through Clay Bath Systems

Abstract

The palm oil industry (POI) generates significant amounts of waste, including calcium carbonate (CaCO3) from the clay bath system used for the separation of palm kernels from shells. This CaCO3 waste is often discarded, leading to environmental issues. However, the CaCO3 can potentially be reused in the clay bath separation process to improve efficiency and reduce waste. To obtain PKO, the kernel is separated from the palm shell using a clay bath unit, where natural CaCO3 acts as a decanting agent and adsorbent. This wet separation method, involving a mixture of water and CaCO3 with a density of 1.12 g/mL, generates substantial amounts of saturated CaCO3 waste that is often discarded into the environment. Therefore, this research aimed to regenerate oil-bound CaCO3 waste for reuse as a decanter and adsorbent. Three treatments were tested, with CaCO3 waste-to-water ratios of 1:1, 1:3, and 1:6, under varying pH levels (8, 10, 11, 12) and temperatures (28 °C, 80 °C, 100 °C). The regeneration process was conducted in an open reactor at 450 rpm with a volume of 0.0054 m3, followed by drying and grinding the waste for analysis. The results showed approximately 75.75% oil removal and CaCO3 regeneration rates between 94.50% and 99.26%, with an increase in density from 1.687 g/mL to 2.467 g/mL. The efficiency of reusing regenerated CaCO3 waste is 96.87%. When mixed with 25% natural CaCO3, the efficiency increases to 99.24%. Additionally, a mixture of 50% regenerated CaCO3 waste and 50% natural CaCO3 achieves an average efficiency of 99.46% over five consecutive feed additions. This showed that the reuse of CaCO3 waste regeneration results for the separation of palm shells and kernels has a high potential for application. These findings suggest that regenerated CaCO3 waste can be effectively reused, offering a sustainable solution for palm oil mills.