By Tim Hoskins, Iowa Farmer Today (Wednesday, August 5, 2009; 2:48 PM CDT)
Online at: http://www.iowafarmer.com/articles/2009/08/06/top_stories/co2.txt
 Detecting mold in grain may best be done by trackinging carbon dioxide levels in bins using a monitor such as the one on the right. Development of mold in grain can be marked by sudden spikes in CO2 levels. Photos from IFT files/USDA-ARS |  |
While farmers are accustomed to monitoring stored grain by moisture and temperature, monitoring the amount of carbon dioxide produced by the grain might be a better way to keep tabs on it.
Paul Armstrong, a researcher with the USDA's Agricultural Research Service in Manhattan, Kan., is studying the monitoring of carbon dioxide in stored grain. Armstrong says monitoring CO2 levels might provide more accurate results to detect if mold is growing.
"It seems like it is simpler," compared with taking temperature and moisture levels, he says.
As mold grows, Armstrong explains it gives off carbon dioxide. Therefore, if there is a CO2 spike, there is likely an increase of mold activity.
"Heat does not transmit through the grain well," he says of using temperature sensors. Temperature and moisture sensors might not take into account the grain history that might make it likely to have active mold growth, he notes.
Armstrong says the CO2 sensors can be placed in the headspace, near the exhaust fans or both.
Carbon dioxide sensors might be able to pick up hot spots of mold activity within a grain bin that other sensors may not be able to detect, he adds.
While he knows measuring CO2 levels works, Armstrong is refining what the numbers mean.
"We can tell you something is not good. We can't tell you how bad it is," he says of using CO2 levels to monitor grain condition.
Normal air concentrations of carbon dioxide run about 400 parts per million (ppm), Armstrong says. In stored grain, CO2 concentration can run up to 1,000 ppm.
If the sensors read more than 10,000 ppm, he says there is severe mold activity. If the readings are 2,000 to 3,000 ppm, there is some mold activity.
Most of Armstrong's work has been with wheat in storage bins. However, in the past few years he has worked with The Andersons Inc. in Indiana monitoring CO2 levels in the company's corn with hand-held sensors.
He also is working with the rice industry. Armstrong says the popcorn industry could be another market to monitor CO2 levels.
Overall, he says there is more work to be done to refine the numbers and how to interpret them.
It will be a few years before CO2 sensors will become available for commercially, Armstrong says, adding there is a need for more research in commercial settings to refine the numbers.
He says there is the possibility of adding a radio transmitter to the sensors that would transmit the readings electronically.
Armstrong also is researching how to measure and use information about relative humidity in stored grain and to preserve grain quality. |
