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United States Department of Agriculture

Agricultural Research Service

Title: Simultaneous monitoring of stored grain with relative humidity, temperature, and carbon dioxide sensors

item Gonzales, Haidee
item Armstrong, Paul
item Maghirang, Ronaldo

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 7/1/2009
Publication URL:
Citation: Gonzales, H., Armstrong, P.R., Maghirang, R.G. 2009. Simultaneous Monitoring of Stored Grain With Relative Humidity, Temperature, and Carbon Dioxide Sensors. Applied Engineering in Agriculture. 25(4):595-604.

Interpretive Summary: A simulated grain storage was monitored during aeration to determine if a high-moisture grain in the bin top could be detected using relative humidity (RH), temperature (T), and carbon dioxide (CO2) sensors. RH and T sensors data were combined to indicate the equilibrium moisture content (EMC) of the grain. Sensors were placed at different depths in the bin. The wet grain produced high amounts of CO2, which, in most cases, was easily detectable during aeration. Lowering grain temperature with aeration diminished the amount of CO2 produced making it more difficult to detect unless the CO2 sensor was located very close to the wet grain. The moisture content of the grain increased downstream of the high-moisture grain during aeration as indicated by the EMC data. Simultaneous monitoring of stored grain with these sensors should improve storage management by detecting problematic conditions quickly so corrective measures could be taken.

Technical Abstract: Grain moisture content (MC) and temperature (T) are the primary factors affecting grain deterioration in storage. If these factors are not properly monitored and controlled, grain quality can deteriorate quickly due to mold growth and insect infestation. This research examined use of relative humidity (RH), T, and carbon dioxide (CO2) sensors for their suitability to determine adverse storage conditions of wheat. A mock-up storage system was constructed and used to simulate a wheat storage bin 6.86 m deep. Sensors for T, RH, and CO2 concentrations were placed at various depths in the storage. High-moisture grain, comprising about 11% of the grain volume, was placed in the top section of the bin to simulate adverse grain condition. Aeration of wheat was done with the high-moisture grain conditioned to nominal MCs of 14%, 16%, and 18% wet basis (MCwb) and the remaining grain at approximately 11% MCwb. Sensors monitored air conditions during the entire storage period. Aeration was provided over 3-h periods at rates of 0.083 m3/min/tonne (8 experiments) and 0.166 m3/min/tonne (1 experiment). Airflow was from top-to-bottom of the bin. CO2 sensors were effective in detecting moist grain conditions but were less effective at lower grain T. In addition, CO2 levels monitored at the exhaust of the aeration duct were adequate in determining adverse storage conditions. The equilibrium moisture content (EMC) of wheat, determined from RH and T, gave reasonably accurate measurements of grain MC. EMC measurements were also effective in determining moisture changes in the grain due to the moisture front movement from the high-moisture grain.

Last Modified: 10/17/2017
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