Rethinking the Humble Brick

A People have been making bricks for thousands of years, and the basic method has hardly changed. Clay is dug from the ground, mixed with water, pressed into a mould and left to dry. The shaped blocks are then fired in a kiln at temperatures of around 1,000°C until they become hard and weather-resistant. A builder from centuries ago would recognise almost every step in a modern brickworks.

B That familiar process, however, carries a heavy price. Heating a kiln to such high temperatures, often for several days, requires enormous amounts of fuel. In the region of Moravel, where brickmaking is a major industry, a recent survey estimated that the kilns alone used more energy each year than all the homes in the regional capital. Most of that energy still comes from burning coal or gas.

C One research group believes the kiln could be avoided altogether. At the Lindqvist Materials Laboratory, scientists mix sand with a harmless type of bacteria and a nutrient solution. As the bacteria feed, they produce a natural mineral that binds the sand grains together, much like cement. After about five days at room temperature, the result is a solid block strong enough for garden walls and small buildings.

D Other teams are looking at what goes into the brick rather than how it is hardened. Ash left over from burning rice husks, crushed glass from recycling centres and rubble from demolished buildings can all replace part of the clay. Using these materials keeps waste out of landfill and, because some of them melt at lower temperatures, can also reduce the heat needed in the kiln.

E Despite these advances, new bricks are appearing on building sites only slowly. Builders are understandably careful about using untested materials in structures meant to last a century. Building regulations often demand many years of performance data before a new product can be approved, and small production runs mean the alternatives currently cost more than ordinary bricks.

F To gather that evidence, a primary school in the town of Everholt has been built using 40,000 low-energy bricks. Sensors inside the walls record temperature, moisture and any movement in the structure, and the data are sent to researchers every hour. If the bricks perform well over the next ten years, the project's organisers hope the results will persuade regulators and builders alike.