Graham Thorpe PhD(Nott), DEng(Melb)

Graham Thorpe’s research impinges on two important global issues, namely food security and energy conservation.

Food security: In 2023 The World Economic Forum estimated that 343 million people were subject to food insecurity. The problem is exacerbated by the fact that 50-60% of cereal grains such as wheat, rice and barley are destroyed during storage. The losses are typically caused by grains being consumed by pest insects, and attacked by fungi. These losses can be reduced to less than 2% by employing simple but effective storage strategies.

Half a century ago, insects in Australia were controlled by spraying almost all grains with pesticides. However, insects became resistant to pesticides, and grains treated with pesticides were eschewed by consumers. A range of physical methods has been considered to control insects. They include percussion that occurs when grains collide with fixed surfaces, suffocation of insects in oxygen-reduced atmospheres, rapidly heating grains to a temperature of 65°C, and cooling grains by ventilating them with ambient or refrigerated air.

Grains are protected from attack by fungi by drying them to ensure that they are in equilibrium with air that has a relative humidity less than about 70%. Cereal grains, oilseeds and pulses are hygroscopic – their moisture contents depend on the temperature and humidity of the atmosphere. This has a profound effect on their behaviour during storage. Research is being carried out on manipulating conditions within grain stores to make them inimical to the growth of insect populations, and to preserve valuable properties of stored grains. A particular emphasis is the effect that the hygroscopic properties of grains have on the management of storage systems.

Low energy air conditioning: A cool environment improves health and productivity. However, the International Energy Agency (IEA) reports that of the 2.8 billion people who live in the hottest regions of the world only 8% have air conditioning. This contrasts with 62% and 76% in Queensland and Western Australia respectively.

The IEA projects that by 2050 the growth in energy used for cooling buildings will have increased so much that the additional electricity generation capacity required for cooling buildings will equal that of the present generating capacity of the US and Germany combined. Air can be dried by forcing through beds of desiccants, and this has led to the development of a novel air conditioning system.

Desiccants and food grains share a property, namely they are hygroscopic. Stored grains can be cooled by ventilating them with cool air during the night. However, the relative humidity of air is high at night, and this lowers its ability to cool grains. Research at Victoria University has shown that air may be dried by passing it through a bed of desiccant, and this renders it suitable for cooling grains.