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# Grain Drying - Frequently Asked Questions

 Agri-NewsThis Week

What are custom rates for grain drying?
According to recent Alberta Agriculture surveys, grain drying costs ranged from \$45-75/hr, or \$10-12/T, or \$0.15-0.24/bu. These costs will vary from year to year as energy costs fluctuate. The amount of moisture that needs to be dried out of the grain will also affect the total costs.

How long does it take to dry grain?
Grain drying time depends on the size and efficiency of the dryer, the moisture content of the grain and the volume or weight of grain to be dried. The drying time for grain is probably best illustrated with an example calculation.
• It takes about 1500-2500 BTUs to evaporate 1 lb of water. The manufacturer of the grain dryer should be able to provide these specifications. For this calculation the energy requirement is assumed to be 2000 BTUs/lb.
• The heating rate in BTU/hr is usually stamped on the dryer or heated aeration unit. For this calculation it is assumed to be 40,000 BTUs/hr
• The weight of water in barley at different moisture contents is given in Table 1.
• Assume 2000 bu of barley that is originally at 19% moisture and want to dry it down to 14.8% moisture.

Table 1. Weight of water in barley at various moisture contents

 Moisture Content % Lbs of Water per bushel 25 13.6 22 11.5 20 10.2 19 9.6 18 9.0 17 8.4 16 7.8 14.8 (dry) 7.1
• Weight of water to remove: 9.6 lb - 7.1 lb = 2.5 lb/bu
• 2000 bu X 2.5 lb/bu = 5000 lb of water to remove
• 5000 lb X 2000 BTU/lb = 10 million BTUs needed
• 10 million BTU / 40,000 BTU/hr = 250 hr = 10.4 days
What are the costs per bushel for this grain drying?
Again this is probably best illustrated with an example calculation using several assumptions. Keep in mind that this example includes fuel costs only and does not include the additional costs of labor, electricity, grain handling, depreciation, and other less direct costs.
• 1 gigajoule (GJ) = 1,000,000 BTU (1 GJ/1,000,000 BTU)
• Natural gas costs \$5/GJ
• Weight of water to remove: 9.6 lb - 7.1 lb = 2.5 lb/bu
• 2.5 lb/bu X 2000 BTU/lb = 5000 BTU/bu needed
• \$5/GJ X 1GJ/1,000,000 BTU X 5000 BTU/bu = \$0.025/bu
What are the maximum drying temperatures for grain?
The high temperatures in grain dryers can damage the grain. The maximum allowable air temperatures for drying will depend on the crop in question and the end use of that crop (Table 2). Note that the values given in Table 2 are air temperatures going into the dryer and are not the temperatures of the grain itself.

Table 2. Maximum allowable air temperatures for grain drying

 Seed Commercial Feed Wheat 60 °C 65°C 80-100°C Oats 50°C 60°C 80-100°C Barley 45°C 55°C 80-100°C Flax 45°C 80°C 80-100°C Canola 45°C 82°C --- Peas 40°C --- 45°C

How much drying can be expected with aeration?
The primary purpose for aeration is to achieve or maintain a uniform grain temperature throughout the bin. Some drying can occur in aeration systems, but generally grain going into aeration bins should be within about 1% of being dry enough for long term storage.

Cereal Grain Drying and Storage

Prepared by Ag-Info Centre, Alberta Agriculture & Rural Development

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