Continuous microwave drying of the seeds of the invasive Chinese tallow tree.
The Chinese tallow tree (CTT) (Triadica sebifera) is an invasive species in the Southeastern portion of the USA. With lipid content between 40% and 55%, the tree's non-edible seeds are a valuable source for biofuel production. In situ transesterification is a proposed method for optimizing the transesterification process since it does not require prior oil extraction; however, for yields greater than 98%, the moisture content of the seeds should be less than 2%. In this paper we highlight an innovative microwave assisted drying method, used for the first time for these seeds, as a solution which drastically reduces the drying time and energy consumption compared to other drying methods. To optimize the microwave-assisted drying of CTT seeds, temperatures of 25 and 55°C were tested with microwave powers of 0, 200, and 600 W using a continuous microwave drying system. The decrease in moisture content is greatest at 600 W of microwave power, with ambient temperature having little effect on the heat generation. The drying rate to power consumption ratio is greatest with a combination of 600 W at 25°C ambient temperature. The microwave assisted drying reduced the drying time to about 300 seconds compared to the 4 h required for conventional oven drying.