Optimization of waste tobacco stem expansion by microwave radiation for biomass material using response surface methodology

Biomass material from stem granules made of waste tobacco stem can be applied in reducing harmful component in a cigarette. Response surface methodology (RSM) was used to optimize the parameters of expanding tobacco stems via microwave radiation method for preparing the biomass material from stem granules. The effects of steam pressure (0.15-0.35 MPa), microwave power (5-6 kW), and drum rotation frequency (15-30 Hz) on expansion rate were studied. Furthermore, the microstructure, conventional chemical compositions and aromatic components of tobacco stems expanded under the optimum conditions and the non-expanded tobacco stems were analyzed by continuous flow analyzer, GC-MS and scanning electron microscope (SEM). The results show that RSM was adequate to describe the relationship between the independent variables and the expansion rate. The expansion rate of tobacco stems was significantly affected by these three variables. The optimal steam pressure, microwave power, and drum rotation frequency were 0.35 MPa, 6 kW, and 15 Hz, respectively. Under optimal conditions, the expansion rate of tobacco stems was 261.12%. The relative error differed by only 3.45% from model predictions, which confirmed the validity of the model experimentally. The optimal parameters obtained by microwave expanding waste tobacco stems have laid the foundation for the preparation and further study on the biomass material from stem granules. (C) 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.