In Argentina about 35 million tonnes of grains were stored in hermetic systems (silo-bags) during 2007, and it is expected that in the future a bigger proportion of the grain will be stored in these silo-bags in Argentina and other countries.
Early detection of spoiled grain stored in hermetic plastic bags (silo-bags) using CO2 monitoring
The silo-bags are made of a 235-micrometer plastic film of 2.74 m diameter and 60 m long (holding approximately 200 tonnes of wheat each). Grain quality monitoring is carried out with a standard torpedo probe. This operation has several disadvantages, including perforating the plastic film (disturbing the air tightness of the system), difficulties to target the grain spoilage area (especially when it is located in the bottom of the silo-bag), and the relatively intense labor demand. Monitoring stored grain conditions through temperature measurement is not an option, since the grain stored in the silo-bags does not increase temperature during spoilage.
A study was made with several silo-bags filled with wheat and soybean located at different farms and grain elevators in the South-West of Buenos Aires province. The silo-bags were sampled with a torpedo probe, and the corresponding value of CO2 concentration of the silo-bag was measured. The collected grain samples were analyzed in the laboratory for moisture content (MC). Additionally, the silo-bag overall condition was evaluated (bad sealing, openings, occurrence of occasional flooding in the area of the silo-bag, etc), and evidence of spoiled grain at bag unloading was collected.
Periodic CO2 monitoring of silo-bags allowed for the early detection of biological activity and spoiled grain. A distinctive value of CO2 for different MC grains was established, which represents the typical atmospheric composition for a silo-bag with and without conservation problems. The silo-bags holding grains with different levels of conservation problems were identified by the unusually high CO2 concentrations of the modified atmosphere.