Safe grain storage poses a major challenge after harvest. Traditional granaries are prone to grain heating, mildew and pest infestation, resulting in staggering annual grain losses. Nowadays, the controlled atmosphere grain storage technology is solving this problem, with air compressors serving as its core equipment.

Simply put, the air compressor compresses air, which is then sent to a separation device to extract nitrogen that accounts for about 78% of the air. High-purity nitrogen with a purity of over 99.5% is pumped into sealed granaries through pipelines to displace internal oxygen. When the oxygen concentration drops below 2% and nitrogen concentration stays above 98%, pests cannot survive — most stored grain pests suffocate to death within days in oxygen-free environments. Meanwhile, mold growth is effectively inhibited, grain respiration is minimized, and abnormal temperature rise is prevented.

Farmers used to fumigate grain with chemical agents such as aluminum phosphide for pest elimination. This method involves operational risks and leaves worrying chemical residues. In contrast, controlled atmosphere grain storage adopts a purely physical pest-killing and mildew-proof approach without any chemicals, which is greener and safer.

In terms of practical effects, grains like rice and wheat can be safely stored for more than 18 months under nitrogen protection and remain fresh when taken out of storage. In terms of costs, despite the initial investment in air compressors and nitrogen-making equipment, the daily operating cost is low. The investment can be recovered in around two years thanks to reduced grain wastage.

At present, this technology has been widely applied in large national grain depots and central grain reserves in China. Large-scale farming cooperatives and major rice mills have also begun to build small-scale controlled atmosphere grain storage warehouses.