Abstract Rotary drum dryers have been used to dry various products, including medicinal and aromatic plants, to reduce postharvest losses. However, no attention has been paid to investigate the drying medium temperature monitoring, which results in a significant loss of the dried products' quality and increases energy consumption, subsequently raising the drying technology carbon footprint. Therefore, a smart hybrid rotary infrared-heater drum was designed, manufactured, and tested. At 30, 40, and 50 °C for each drying system (IR, heater, and IR + heater), the dryer was examined by assessing the monitoring and control of the drying temperature, drying kinetics, and energy consumption, and its influence on the lemongrass herbs’ quality. The findings showed that the shortest drying time and highest drying rate were achieved with the IR + heater. Moreover, the application of the intelligent system for monitoring and controlling the drying temperature reduced the drying time by values of 9.2, 6, and 3.2 h, and 8.3, 5.7, and 2.6 h at drying temperatures of 30, 40, and 50 °C for the IR and IR + heater, respectively. The highest energy-saving percentages, 71%, 61%, and 37%, were achieved with the IR + heater system at 30, 40, and 50 °C, respectively. In addition, IR + heater drying at 40 °C significantly improved lemongrass quality by up to 2.80 ± 0.33%, preserving photosynthetic pigment content, and enhancing antioxidant activity. Therefore, employing IR + heater as a hybrid system attached to a rotary drum dryer offers a sustainable and environmentally energy-efficient method while ensuring quality retention in dried lemongrass. Graphical Abstract
Ibrahim et al. (Mon,) studied this question.