With higher costs of electrical energy, propane and natural gas this fall, producers are looking for ways of holding down their energy costs for finishing their crops. One option producers may have, if their grain handling systems are properly set up for this option, is natural air drying for shelled corn.

Natural air-drying systems can dramatically reduce energy inputs for drying. For example, drying corn from 25.5 to 15.5% moisture content with a natural air system may use as little as 25 to 40% of the total energy of high temperature systems. Natural air-drying replaces the fuel energy, usually propane, by using the natural drying potential of air over a longer period of time. However, more electrical energy is used to move the air through the bin. Total energy cost will depend on fuel and electric energy costs but will generally be lower for natural air systems.

Natural air grain drying systems do require close monitoring to reduce the risks of grain spoilage. For more detailed discussion about recommended airflow rates for specific grains at various moisture contents, effects of bin diameters and grain depths, fan selections, how to determine when grain drying is complete and other specifics of natural air grain drying, view the following two publications:

http://ohioline.osu.edu/aex-fact/0202.html

http://www.extension.umn.edu/distribution/cropsystems/DC6577.html

Good management practices that will reduce risks, assist in working with the grain, and increase success of operating a natural air grain drying system include:

1. Grain should be free of excess dirt, fines, and chaff. Cleaning devices are recommended. Not cleaning these materials out of the grain mass can result disruptions of air flow through the entire mass. Areas of heavy deposition of these materials can be so dense that moisture and temperature can not be altered.
    
2. Keep grain level as bin is filled. Grain leveling devices are recommended. Peaks on top of the grain mass are also difficult to manage with aeration. Air, like water, will travel the path of least resistance. Air will more quickly exit a grain mass through the lowest edges of peaked grain leaving the center of the peaked grain un-aerated.
    
3. Aeration fans should be started as soon as the bin floor is covered with grain and operated continuously until the grain is dry or the average air temperature is below 35 F for extended periods.
    
4. Leave all roof hatches open to provide a large air exhaust opening, approximately 1 sq ft for each 1,000 cubic feet per minute of air delivered to the bin.
    
5. Circular stairs up the outside of the bin should be included as standard equipment to facilitate safe and frequent grain inspection.
    
6. Attach a manometer to the air plenum to measure static pressure and use manufacturer's fan performance charts to determine airflow.
    
7. When the daily average temperature drops below 35 F, cool the grain to a uniform temperature and turn the fan off (below 35 F drying is slow and inefficient). If moldy odors are detected or the grain starts to heat, turn the fan on until the conditions are corrected. Continue the drying process when the average temperature returns to 35 F or above.
    
8. After drying is completed, close the roof hatches and cover fan inlets to prevent migrating air from adding moisture to the grain.
    
9. Do not exceed design criteria for the aeration fans. When necessary, limit grain depth to obtain proper airflow in relationship to the grain moisture content.
    
10. Follow safety rules at all times while working in or around grain bins and drying equipment