This is the VOA Special English Technology Report.

A few degrees can make a big difference when it comes to food storage. Foods can go bad if they get too warm. But for many of the world's poor, finding a good way to keep food cool is difficult. Refrigerators are costly and they need electricity.

Yet spoiled food not only creates health risks but also economic losses. Farmers lose money when they have to throw away products that they cannot sell quickly.

But in nineteen ninety-five a teacher in northern Nigeria named Mohammed Bah Abba found a solution. He developed the "Pot-in-Pot Preservation/Cooling System." It uses two round containers made of clay. A smaller pot is placed inside a larger one.

The space between the two pots is filled with wet sand. The inner pot can be filled with fruit, vegetables or drinks. A wet cloth covers the whole cooling system.