Sealing of welded-steel hopper bins for fumigation of stored grain with carbon dioxide

Fumigation of grain with carbon dioxide (CO2) requires the maintenance of high CO2 concentrations (20 to 60% by volume in air) for extended periods (> 4 d). Grain storage structures currently used on Canadian farms are not airtight and should be sealed if they are to be used for fumigation with CO2. Various sealing techniques were applied to two welded-steel hopper bins to improve their gas-tightness. Each sealing technique was tested by adding 136 kg of dry-ice pellets to a steel box connected to the empty bin by ABS piping. If the CO2 displaced air, this would have created a CO2 concentration of approximately 65% inside the empty bin. Carbon dioxide concentrations continually increased as the sealing improved, but never reached 65%. Uniformity of CO2 within the bin in both the radial and vertical directions also improved as the sealing improved. Fumigating with CO2 using this type of bin will be possible if either 1) the length of exposure at the lower CO2 concentration is increased, or 2) additional dry ice is added to the bin to compensate for leakage.