Microwave Drying of Banana (Musa acuminata) Stalk Biomass before Conversion to Value-added Products

Abstract

Banana stalk biomass can pose disposal, environmental and health challenges. Fortunately, this biomass can be converted to value-added products including biofuels, bioenergy, biosorbents, fibers and animal feeds. However, it is necessary to remove moisture from the fresh biomass by drying before storage and conversion processes. Conventional drying in open sun is slow and weather dependent, but higher heating rates and faster drying rates can be achieved in a microwave dryer. Hence, the microwave drying characteristic of banana stalk biomass was investigated. Banana stalks were sliced into 5 mm thick pieces and dried in a microwave oven at power levels of 400 – 1000 W, the stalk slices were weighed at interval until the mass remained constant. The effective moisture diffusivity, activation energy and energy required for drying were determined. The microwave drying data were also fitted to twelve thin layer drying mathematical models to describe the kinetics of the drying process. The drying time of banana stalk slices decreased with increasing microwave power. The drying occurred mainly in the falling rate period. The effective moisture diffusivities were 4.14 × 10-9 – 2.00 × 10-8 m2 s-1 at 400 – 1000 W. The activation energy was 122 W g-1 while the total and specific energies required for the microwave drying were 0.25 – 0.37 kWh and 34.8 – 51 kWh/kg, respectively. The Weibull model suitably described the microwave drying kinetics of banana stalk slices. The moisture present in fresh banana stalk waste biomass can be effectively and rapidly removed by microwave drying before conversion processes.