Building a better brick.

Just another brick in the wall? Not exactly. Partners in a Danish housing project have just finished using a new recycled brick in the construction of 26 houses. Although there are few firm figures to date, recycling bricks this way is expected to save energy and money, reduce emissions of pollutants such as carbon dioxide during the manufacturing process, and slash the extraction of virgin clay, sand, and gravel. Detailed postconstruction analyses investigating these assumptions should be available over the course of the next year.

The idea for using recycled bricks emerged when the Danish nonprofit housing company Herning Boligselskab asked COWI, a global engineering, environmental, and socioeconomic consulting firm, for ideas on how to make a housing project in the central Denmark city of Herning more environmentally friendly. Along with solar heating, alternative insulation materials, and rainwater for toilet flushing, COWI suggested using miljosten, a patented alternative brick previously used in just one house. The bricks were designed by Stig Maegaard, owner of the small engineering company Ekotek, and Astrup Cement, which manufactures them.

About 95% of each brick is composed of crushed recycled bricks. Mortar granules are added for bonding. Unlike traditional bricks, which must be fired at temperatures of up to 2,000[degrees]f, the bricks are formed at room temperature in molding machines using vibration and high pressure. They have the same density as traditional bricks, says COW1 project manager Niels Moller Jensen, and cost about 10% less to produce. The energy needed to produce l traditional brick can be used to make about 15 recycled bricks. And Jensen says contractors do not need any special skills, techniques, or materials to lay the bricks.

Word of the Danish innovation has not spread widely. Organizations such as the U.S. Brick Industry Association, whose members fire about 8 billion bricks each year, and the U.K. Brick Development Association had not heard of this or similar brick recycling techniques when contacted by EHP. Contrary to Jensen's assertion that no special materials are needed to work with miljosten, Brick Development Association director Michael Driver says there is no lime mortar that works with all types of clays. He adds that some companies are pursuing other "green" brick strategies, such as substituting plastics, glass, or dried, inert sewage for some of the clay content, and using alternative energy sources such as fuel cells for the firing process.

COWI is analyzing the life cycle of the miljosten manufacturing process and impacts on the indoor and outdoor environment, and expects to publish initial findings in December 2003, possibly on Herning Boligselskab's site (http://www.faellesbo.dk).