Briefs: Accessible and free evaporative solution

A simple and ingenious utensil, the zeer pot, makes it possible to extend the shelf life of produce for several days and is becoming very popular in Africa. The system was invented by Mohammad Bah Abba, a Nigerian teacher and consultant to the regional United Nations Development Programme, in the mid 1990s and consists in two earthenware pots of different diameters, one placed inside the other. The space between the pots is filled with wet sand that is kept constantly moist, thereby keeping both pots damp. As the water contained in the sand between the two pots evaporates, a temperature drop occurs. This reduces the temperature of the inner container by several degrees compared with the surrounding environment and helps preserve the perishable foods inside. There are many other ingenious applications of evaporative cooling using porous clay to cool vessels. Such cooling has been used in Qena in Upper Egypt for over three millennia. People in Burkina Faso also soak pots in water for cooling and enclosures made of wet bricks are used in India. The Punjab Agricultural University in Ludhiana has recently tested an improved version of this system, which is closer to the zeer as it uses double brick walls and wet sand between them. It keeps fruit and vegetables at temperatures below 20°C. www.ruralindia.blogspot.com,www.rolexawards.com, www.scienceinafrica.co.za