Protecting high quality legumes, pulses and rice from insect contamination 

A well-established food brand had been respected for years for its quality products, importing legumes, pulses and rice then packaging and distributing for the retail market.

At the source, pests can get into the plants whilst in the field growing and post-harvest during processing and storage. They reproduce continually as long as the conditions are suitable. The customer guarantees its partners that there will be no insects in its products, the absence of all traces of microscopic creatures is therefore crucial.

Currently, insect infestation is controlled by fumigation using an extremely toxic gas, typically hydrogen phosphate. This is associated with safety risks, including the possibility of residues in the product. Insects can also become resistant over time and doses must be increased. If insects encounter a toxin (hydrogen phosphate) in insufficient concentration and they survive, they acquire resistance. This immunity is then passed to their offspring.

A new approach

To overcome this problem, the customer took a fresh approach and in cooperation with the Plant Production Research Institute, started working on a project to control insects using oxygen exclusion with non-toxic nitrogen gas. The nitrogen is injected at a precisely determined concentration into the storage silos, over a period of 10 to 20 days.

This period of time is necessary for the nitrogen created hypoxic atmosphere to work effectively against the insects, larvae and eggs. The larvae and eggs can tolerate a lower oxygen level whilst the adult insects are eradicated relatively quickly. An exposure period in the nitrogen atmosphere of just less than three weeks has been determined as optimum to completely destroy every single pest.

To produce the required volumes of nitrogen gas by the most efficient, cost effective and reliable method possible, a Parker NITROSource PSA system was proposed and installed. Ambient temperature is another factor that needs to be considered in ensuring nitrogen works most effectively in eradicating the insects.

At lower temperatures in the silos, the insect’s metabolism slows and therefore they require less oxygen for respiration, increasing the necessary exposure time required to the hypoxic atmosphere.

Parker’s Distribution partner suggested installing all the equipment including the compressors within the silo storage area. The waste heat from the nitrogen generation system helps to keep the silos and their contents at warmer ambient temperatures and creates the ideal environment for the hypoxic atmosphere to be at its most effective. Not only does the waste heat, warm the silos but it also saves the customer energy costs for heating the warehouse as well as reducing humidity, helping to keep the produce dry.

The customer has subsequently installed two Parker nitrogen systems for two separate silo applications and storage warehouses.

The first system comprises an NITROSource Plus with EST producing up to 67m3 /h @ 0.5%. The pre-treatment used is an heatless compressed air dryer because there is an additional food grade compressed air demand for an optical sorter machine that removes substandard product as it is processed for packing using jets of air.

The second system is also an N2-65P with EST producing up to 67m3 /h @ 0.5% purity but with a dedicated OFAS compressed air pre-treatment package.

Current analysis of the total cost of Parker’s gas generation solution including energy and maintenance demonstrates a 50% saving compared to toxic hydrogen phosphate fumigation without considering the environmental and personnel risk that this process entails.