Controlled Atmosphere Storage Using Carbon Dioxide

Protecting stored grain from insects, rodents and mold has been an ongoing problem since the dawn of agriculture. Early farmers stored grain in pits, urns, bags and baskets. But these storage methods resulted in grain losses approaching half of their total crop!

Today modern grain storage operations use a variety of techniques to limit grain losses. The two most common are chemical and controlled atmosphere storage. Of the two, controlled atmosphere (CA) storage is safer, appears more “environmental” and thus, more desirable.

The most basic CA storage techniques start with grain dried below 12% moisture content before storage. Once the grain is stored, aeration fans are used to ensure uniform temperature and humidity which minimizes mold.

But regulating temperature and humidity isn’t enough. To further pest eradication, agricultural engineers control nitrogen, oxygen and carbon dioxide levels in sealed storage containers to preserve grains and to alert farmers to the presence of destructive insects or mold.

For example, carbon dioxide can be used as a fumigant in lieu of pesticides. According to a report prepared by the Food and Agriculture Organization of the United Nations,

“Insects are generally killed more rapidly by carbon dioxide than they are by lack of oxygen. A concentration of 6 percent carbon dioxide will give over 95 percent control of most stored grain insects after a 4 day exposure at 27°C or higher (Jay, 1971); however, longer periods are needed for complete kill. Banks (1979) suggested that an initial level exceeding 70 percent carbon dioxide and maintained above 35 percent for ten days is appropriate for complete insect control.”

CO2 has an advantage over nitrogen and other chemical fumigation as it does an effective job at killing both anaerobic and aerobic bacteria. In fact, it is nearly as effective as gamma radiation in eliminating bacteria in grains.

Carbon dioxide can also be used as a marker for metabolic processes. Because CO2 is a natural trace gas that comprises only about 0.039% (390ppm) of ambient air, spikes in CO2 levels in a truck, rail hopper car or grain elevator are usually signs of mold or fungi growth.

Custom grain silo CO2 level
control system. Click for details.

CO2Meter.com has been fortunate to work on several CA storage projects. Three of our most popular products in this industry are:

iSense Remote CO2 Storage Safety Alarm – This unit lets you measure carbon dioxide levels in one location and read the results hundreds of feet away on a display. It is perfect for measuring CO2 levels from a trailer or a train hopper car and monitoring the levels from the cab. You can “daisy chain” multiple sensors to a single head unit, and the built-in data logger lets you verify CO2 levels for damaged product insurance claims. Learn more...

iSense CO2 Level Controller & Transmitter – the CO2 level controller monitors CO2 levels, from multiple “daisy chained” sensors, and if CO2 levels are too high, includes an industrial relay capable of running a 250V/10A fan. It can also be used to control CO2 injection projects, like the one shown in the photos. Learn more...

Portable CO2 Sampling Data Logger – This hand-held unit features an internal pump to let you reach deep inside bulk storage bins or silos to take air quality samples. With the built-in internal memory, samples can be taken over time and downloaded to a PC to determine the rate of change of CO2 levels - up means mold or fungus, down means leaks in grain storage containers sealed with CO2 inside. Learn more...

Posted by CO2 Meter on May 22, 2012.
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