Optimization of Microwave Drying Biomass Material of Stem Granules from Waste Tobacco Using Response Surface Methodology

Abstract

Tobacco stems, an underutilized waste in the tobacco industry, can be transformed into a viable product through the preparation of biomass material of stem granules. Response surface methodology (RSM) was used to optimize microwave drying of stem granules from waste tobacco. The effects of microwave power (35–40 kW), moisture content (25–35%), material thickness (30–50 mm), and drying time (90–150 s) on filling power and yield of stem granules were studied. Gas chromatography–mass spectroscopy (GC-MS) and scanning electron microscopy (SEM) were used to determine volatile components and microstructures of stem granules dried under optimal conditions. The filling power and yield of stem granules could be adequately fitted to a quadratic model (R ² = 0.951) and a two-factor interaction model (R ² = 0.887), respectively. The optimal conditions for microwave drying of stem granules were 35 kW, 30%, 30 mm, and 150 s. When prepared under optimal conditions, the filling power and yield of stem granules were 7.94 cm³/g and 64.06%, respectively, which differed by only 4.53 and 3.50% from model predictions. The quadratic and two-factor interaction models provided a reasonably accurate (<5% error) assessment of optimal conditions for microwave drying of biomass material of stem granules from waste tobacco stems.

Keywords:

• Biomass material of stem granule
• Filling power
• Microwave drying
• Response surface methodology
• Waste tobacco stem
• Yield

ACKNOWLEDGMENTS

This work was financially supported by the Science and Technology Department of Yunnan Province (2008IC014). The authors thank the Yunnan Reascend Tobacco Technology (Group) Co., Ltd., for providing the experimental equipment.

Notes

R ² = 0.9510, , adeq. precision = 17.505 (>4).

R ² = 0.8871, , adeq. precision = 18.172 (>4).

ns, Not significant. *Significant at p < 0.05. **Significant at p < 0.01.