When deciding whether to use an existing building for grain storage, estimate how much the building can hold. It may be enlightening to discover how few bushels some flat buildings can actually store, especially if ceilings are low or grain cannot be piled against the sidewalls. Formulas are available to calculate the volume of grain in rectangular or cylindrical structures, as well as in conical piles.
Computations on Grain Stored in Various Configurations. Lancaster County Extension - University of Nebraska.
Grain Storage Tips - Factors and Formulas for Crop Drying, Storing and Handling. University of Minnesota.
Both permanent and temporary storage structures must be sanitized prior to storage, but this process will likely be more difficult with temporary structures. Good sanitation practices will help avoid immediate insect infestation or disease inoculation of the new crop. The building should be thoroughly cleaned and all insects and previous grain, grain particles and feed removed. Be sure to clean under perforated floors and in aeration ducts and grain handling equipment as well as inside and outside of the structure. Consider fumigating any areas that can't be cleaned.
If the building previously contained manure, agricultural chemicals, or petroleum products, completely remove these materials so that the grain will not be physically contaminated or pick up odors that would result in downgrading. After thorough cleaning of the building and equipment, consider spraying the structure with an approved, residual-type insecticide.
Stored Grain Insect Pest Management. Purdue University.
Bird and Rodent Exclusion
Grain losses are unavoidable if birds and rodents have access to the grain. Inspect the storage structure thoroughly to determine how to keep these pests away from the grain.
Check the building for water-tightness during or immediately after a heavy rain. Fix roof leaks if necessary. Be sure there is good drainage that directs water away from the structure rather than onto or under the floor. If the structure has a dirt or cracked concrete floor, it should be covered with 4- to 6-mil plastic to prevent moisture transfer into the grain.
Most farm buildings are not built to withstand the lateral forces of stored grain and need to be reinforced. With some buildings, walls can be strengthened by cables or braces. In most buildings, however, it will be necessary to keep the grain mass from impacting the outside walls, especially if the grain depth is more than two feet at the wall. Using free-standing metal grain bin rings inside a structure is one way to contain the grain. Anchor the rings according to manufacturer recommendations. A 36-foot-diameter ring has a capacity of 800 bushels per vertical foot. Four rings (each 32 inches high) would have a capacity of 8,500 bushels. The cost of the rings is reasonable, given today's corn grain price. Aeration system designs are simple with these rings as well. Rings can also be built of plywood (see links below for more information.)
Other options to keep the grain mass away from the walls of the building include free-standing bulkheads and portable, self supporting grain walls constructed of plywood and lumber. These structures can be used to convert all or part of a building to grain storage. See engineering instructions that account for the force of the grain mass and the strength of the building materials to construct an adequate grain containment wall. Ag engineering publications available for this purpose include:
Temporary Grain Storage. North Dakota State University.
Temporary Grain Storage Considerations. Kansas State University.
Grain quality cannot improve in storage -- it can only diminish. For that reason, good initial grain quality is key to maintaining quality throughout the storage period. Good grain quality begins in the field with managing insects and diseases and scheduling harvest based on field condition and proper grain moisture. Insect-damaged kernels may become diseased, or break with harvest and handling. Kernel rots that begin in the field will continue in storage if moisture and temperature are not strictly controlled. Corn harvested too wet may be badly damaged during combining.
Careful grain movement and low-temperature drying are also important to minimize broken kernels and stress cracks that lead to eventual breaking. Intact kernels resist mold and grain deterioration. Broken kernels and "fines" block air movement in storage and lead to "hot spots" of spoiled grain in the bin. Rotary screens, gravity screens or perforated auger housing sections can remove broken kernels and fines prior to storage. If grain has poor quality, with excessive broken kernels, fines, kernels rots, and/or foreign material such as weed seeds or trash, it should likely not be stored. If stored, it should be screened and dried to at least one percent lower moisture content than that of good quality grain.
Achieving and maintaining "equilibrium" grain moisture throughout the grain mass is the key to successful corn storage. Ideally, corn grain moisture should be maintained at 15 to 16% or below for long-term storage. Corn can be stored at higher moistures, but its shelf life will be reduced. Temperature is the other critical factor that determines shelf life of grain. Shelf life is a function of grain moisture and temperature as shown in Table 1. The storage times indicated in this table are not based simply on initial grain moisture, but on maintaining the indicated moisture by aeration. Unaerated corn may deteriorate three times faster than indicated in Table 1.
To prevent moisture migration within the storage structure, air must be circulated through the grain mass at a rate of at least 0.1 cfm (cubic feet per minute) per bushel of grain. This airflow rate applies when outside air temperatures are moderate during late fall, winter and early spring. This rate of 0.1 cfm is not sufficient to dry grain, but only to maintain the initial storage moisture content of the grain. To maintain grain moisture when grain is above 17% moisture or temperatures are above 70 F, airflow rates of 1/3 to 1/2 cfm/bu are required. Much higher airflow rates are needed to dry corn in storage.
Large round or square bales can be used as walls to contain outside grain storage. A circle of bales with a 40-foot inside diameter, 5 feet high, with grain peaked 9.3 feet higher than the bales in the middle and extending onto the tops of the bales, would contain about 8800 bushels of grain. When covered with plastic, this peaked grain arrangement provides a nicely sloped roof to drain water off the pile to the outside of the bales. Lining the inside of the bales with plastic will help to keep grain in and moisture out. Bales must be tied together with restraining cables or otherwise anchored to resist the outward forces of the grain.
Outside Piles Another option for temporary grain storage is outside piles. Outside piles are not unusual in corn-growing states when yields are high and corn volume exceeds regular storage capacity. Construct the pile on high ground crowned in the middle for drainage away from the pile. Use 4 to 6 mil plastic as a floor to prevent moisture transfer from soil to grain. The pile must be covered with plastic and aerated with perforated pipe to control temperature and moisture.
Emergency Storage of Grain: Outdoor Piling. Kansas State University.