The effect of moisture content on the acoustic characteristic of bioenergy feedstocks—Corn Stover

Abstract

Corn stover is increasingly being used as a bioenergy feedstock. From harvest to handling and storage, its inconsistent moisture content imposes limits on the industry's growth and profitability. We propose an acoustic approach that can detect changes in corn stover moisture content and shows the capability to propagate through corn stover and improve the moisture sensing range and accuracy as compared to currently available technologies. Using air-coupled transducers that operate at 20 kHz and a simple experimental setup, we determine the sound speed in corn stover. Signal analysis using cross-correlation and fast Fourier transform allows the calculation of sound speed and signal amplitude from the A-scan. An inverse relationship between the sound speed and the packing density of corn stover is found. Sound speed and transmission amplitude data enable the determination of corn stover’s moisture content between 10i% and 55%. The benefit of this technology also lies in its ability to sense through the center of a packed sample of corn stover at a density above 300 kg/m3. The improvement promises a decrease in the cost of handling and processing, which will help establish corn stover as an economically-viable bioenergy feedstock.