Sustainable calcium stearate grease from canola-derived TMPTE: Microwave process optimization

The transition from mineral-oil-based to renewable lubricants for industry is dependent on the creation of grease formulations with appropriate consistency, water resistance, and efficient processing. In this study, a calcium-stearate biogrease was produced from canola-derived trimethylolpropane triester (TMPTE) using a laboratory-scale microwave-assisted system. The process was evaluated for thickener concentration of 20–30 wt%, stirring speed of 300–500 rpm and microwave power of 400 – 800 W; the dropping point and electrical energy consumption were used to determine the power level that provides a practical operating condition for the process. Under these conditions, the biogrease had a measured dropping point of 114 °C, which was very close to the predicted dropping point of 112.8 °C and the energy consumption for the process was 1.37 MJ per batch. The final product showed a penetration value of 274 (0.1 mm), corresponding to NLGI grade 2, and a water washout loss of only 1.5% at 79 °C. These measurements indicate NLGI 2 consistency and low water washout under the specified test conditions, but they do not establish full service performance. Compared with a previously reported conventional TMP-ester grease process, the microwave-assisted route eliminated the prolonged 1–3 h high-temperature holding stage and followed a simpler thermal schedule. The results support microwave heating as a promising route for shortening the thermal schedule and reducing measured batch energy, while further temperature mapping and performance characterization are required before broader application claims.