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  • Termites could give clues to energy efficient buildings


African termite mounds could help scientists develop energy efficient buildings that can adapt to an increasingly changing climate and atmosphere, according to Rupert Soar, of Loughborough University's School of Mechanical and Manufacturing Engineering.

To test this idea, Soar will travel this week to Namibia, where he and his colleagues will spend the next three years studying the structure of termite mounds.

Termite nests are large mud structures that average three metres in height, and extend down into the ground. They are remarkable for the way they maintain stable internal temperature and humidity despite variations in the environment that surrounds them.

Evidence suggests that the temperature inside termite nests rarely varies by more than a few degrees, though outside temperatures can range from below freezing at night to 40 degrees Celsius during the day.

Researchers believe the structure of fine tunnels and ducts inside the mound play an important role in regulating temperature, as well as moisture levels and the replenishment of oxygen.

It seems that different parts of a mound's structure control different aspects of the nest environment. Moisture, for instance, appears to be regulated both in the mound's underground 'cellar' and possibly through evaporation from the top of the mound.

And although the termites must generate waste, none ever leaves the mound, indicating that there is some kind of internal system for recycling waste.

But what is most remarkable is that all this is achieved without drawing any energy from the outside world, or, as Soar puts it, "they do it without being near the power station".

  Ruelle filled a mound with cement to produce this 'negative cast' of a nest
Ruelle filled a mound with cement to produce this 'negative cast' of a nest (Photo Credit: Jean Ruelle)
Few details are known about the mounds' internal structure. The closest anyone has ever come to understanding it was in 1962, when entomologist Jean Ruelle filled a nest with cement, then washed away the mud to reveal a 'negative cast' of the structure (see picture).

This was the first indication of the mounds' complex array of channels, which split into smaller and smaller channels, much like a person's blood vessels.

To reveal the structure, Soar and his colleagues will fill and cover termite mounds with plaster of Paris, then take sequential pictures as they slice through each one, one millimetre at a time. The complete series of images will enable them to recreate a three-dimensional model of the mound.

If, as Soar hopes, the structure explains how termite mounds are able to regulate their internal environment without drawing on any external source of energy, the findings could be invaluable in informing future building design.

"As we approach a world of climate change, we need buildings that are more responsive to our environment," says Soar. If the average temperatures rise, he explains, there will not be enough energy to power air conditioners around the world.

"Termites control and trap energy to drive biological function within what is essentially a pile of mud," he says.

The implications for human waste management go beyond the potential of building houses that recycle their own waste. The construction industry is in fact already building structures that can themselves be entirely recycled.

Soar and his colleagues have been collaborating with a major UK manufacturer of gypsum — the mineral used to make plaster of Paris — to create large panels that could serve as the walls of a building. These have integrated cellular structures, much like the interior structure of a leaf stem. As they are made of a single material, they can easily be reduced to powder and reused.

"The construction industry produces a huge amount of waste," says Soar. "What we see in termite mounds is a single material that is modified cleverly so it has the properties of many, many different materials."

Soar is working closely with experts in termite mound structure, such as Scott Turner of the State University of New York College of Environmental Science and Forestry in the United States, Eugene Marais from the Namibian National Museum, and researchers at the Omatjenne Research Station, Namibia.

Together, they hope to make create an international centre for expertise for termite mound research based at the Omatjenne Research Station.
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