Detection of a Developing Hot Spot in Stored Corn with a CO2 Sensor

The primary objective of this study was to determine the effectiveness of detecting a hot spot primarily due to spoilage of high moisture corn in a stored grain bulk with a CO2 sensor installed in the headspace of the bin compared to detecting with temperature cables. Three experimental trials were conducted in a 12.5-t pilot-scale bin from September 2001 to March 2002. A hot spot in the grain bulk was initiated by dripping a controlled amount of water into a confined grain mass held in five layers of cylindrical mesh trays within the grain bulk. Temperature sensors in the core of the hot spot formation monitored its progress and confirmed biological activity, which paralleled the increasing CO2 concentration recorded by the CO2 sensor in the headspace of the bin. CO2 concentrations in the bin headspace rose from the initial base level of 500 to 1500 ppm for Trial 1, 1700 ppm for Trial 2, and 2300 ppm for Trial 3 and were recorded after 400, 600, and 1800 h, respectively. There was a strong positive linear correlation between the rise in headspace CO2 concentration and the parallel rise in temperature recorded by sensors in the core of the hot spot during all three trials. Field tests of spoilage detection with a CO2 sensor conducted in 33,000- to 51,000-t grain piles and a 12,500-t cylindrical steel tank with stored corn indicated that a CO2 sensor was effective in detecting the occurrence of spoilage in the stored grain and detected spoilage earlier than temperature cables. Spoilage detection was effective either by measuring CO2 concentration of the air stream from a negative draft aeration duct with a handheld CO2 sensor, or by installing a wall-mounted CO2 sensor in the tank headspace. Our results show that temperature cables alone might not be a reliable indicator of stored grain conditions and CO2 sensors could be used as an additional complimentary tool for stored grain management.