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Bio building bricks. Using sludge in bricks: Improves quality Reduces weight Saves energy

By Peter TongeStaff writer of The Christian Science Monitor / July 5, 1988



Bowie, Md.

THE building is attractive and functional, a picnic shelter built of quality face bricks, worthy of any building in the country. It should last for a century at least, probably much longer. Tom Shaw would have rejoiced at the thought. He's the Englishman who, exactly 100 years ago, developed a method for making the type of bricks used in erecting the shelter, another like it, and two large maintainance buildings in the Washington, D.C., area. Shaw surprised everyone at the time by making his bricks with sludge - sewage sludge that is. He was granted patent rights in 1889.

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But the invention was ahead of its time. Sludge presented few disposal problems a century ago, and when concern began to surface toward the end of World War I, Shaw's idea was forgotten, lost in the dusty archives of a nation preoccupied with war. Now its time may finally have come. Drs. James Alleman at Purdue University and Ed Bryan of the National Science Foundation in Washington are among those who feel it has.

In this century, sludge volumes have increased geometrically, and disposal problems have been compounded by industrial contaminants. Ideally, clean waste could be composted or applied directly to the land as a fertilizer indefinitely. It has proven most effective in restoring vegetative cover to mine tailings and other scars of the mining industry.

But that still leaves a high percentage, too contaminated with heavy metals from industrial waste to go this route. As a result, research into encapsulating the waste in ceramic materials has become fairly widespread - and Shaw's ideas have surfaced again.

In the United States, much pioneering work on the concept was done by Dr. Alleman while he was at the University of Maryland. He had already made his first experimental bricks in the laboratory kiln when he uncovered the Shaw patent.

In many ways sludge is the ideal additive to the clay-shale mix of bricks. How can that be? Because it is an organic material with the added advantage of being wet. Organic additives improve laying qualities of bricks.

From the mason's point of view, pure clay makes for a less-than-ideal brick. There was even a time when masons considered English bricks more satisfactory to lay than the American-made variety. They accepted mortar more readily, providing a suction that held the brick in place while the mortar began to set.

Investigation showed that English bricks were lighter and slightly more porous, the result of organic ``contaminants'' in the original clay. When fired, the organic material burned up, leaving tiny voids throughout the brick. It has become a common practice to include some organic materials in the clay mix for most though not all brickmaking. Sawdust and coal fines are commonly used, according to Donald Agee, plant manager for the Maryland Clay Products brick company, which has made approximately half a million of the experimental sludge bricks.