The next time nature calls it may be comforting to know that you could be contributing to the construction of a new house.

James Alleman, 32, an environmental engineer who lives in Bowie and teaches at the University of Maryland, has devised a way to make bricks out of sewage. He calls them -- guess what? Wrong. He calls them biobricks.

Although the process is still in the experimental stage, bricks consisting of 30 percent sludge and 70 percent clay and shale have been produced successfully.

Biobricks don't smell bad because temperatures inside the kiln reach 2,000 degrees Fahrenheit during baking, causing odorous gases to be released and purifying the organic materials left behind.

Alleman, who received his bachelor's, master's and PhD degrees from the University of Notre Dame, first got the idea of recycling human waste while serving in the Army in Japan from 1973 to 1976. That's when he learned that the Japanese combined sludge and cement to make large building blocks.

"It wasn't until I came to Washington (in 1978) that I became interested in sludge because it's such a problem here . . . . Blue Plains (sewage treatment plant) alone generates 1,400 tons of sludge a day.

"My students kept talking about it, and one student in particular, Mark Prouty, was working at Blue Plains. I told him about the blocks in Japan and we decided we'd try to make some ourselves," explains Alleman, who grew up in South Bend, Ind., is married and has three children.

The magnitude of sewage treatment and disposal in the Washington region is best illustrated by the 309 million gallons of waste treated each day at Blue Plains, which processes 80 percent of all sewage in the metropolitan area. Blue Plains, or if you prefer, "Pew" Plains, is one of the 10 largest treatment plants in the country.

Prince George's County contributes more than 49 million gallons a day (mgd) to Blue Plains and Montgomery County pours a whopping 71 mgd into the giant facility, which is located in the southwest corner of the District, bordering Prince George's County, and along that portion of I-295 where people can be seen frantically rolling up the windows in their cars.

Now that's a lot of, well, sludge. And there's more. The total amount of sludge currently being created by Prince George's County is 98 mgd, and by Montgomery County, 72 mgd.

It was soon after learning these figures that Alleman began looking into making biobricks.

His initial effort produced a slightly warped brick with large cracks in it. But the substance was rock solid and withstood much testing abuse, and the pair knew they were on to something.

So was T. Shaw of Manchester, England, in August 1899 when he applied for the only patent that now exists for sludge bricks. The patent, discovered by Alleman one afternoon when he was preparing to patent what he thought was an original idea, simply reads: "The sludge is mixed with an equal amount of clay and burnt."

Processes similar to Alleman's are being tried in the United States, according to the professor, by a Midland, Mich., company that adds sludge to concrete, and by a New Orleans firm that makes an asphalt base for roads by mixing sludge, silica gel and cement.

The ancient Egyptians, according to some historians, also made bricks from human waste, but nobody patented inventions in those days.

After learning of T. Shaw's patent, Alleman scrapped his own patent hopes and got on with writing a grant request to the National Science Foundation. A year ago, the foundation gave him $40,000, which will finance his biobrick project until next spring.

"At this point we've proven that we can make nice bricks, only on a bench scale (primitive) basis," says Alleman, who gives much of the credit for the success so far to Neil Berman, 24, of Randallstown, a graduate student who has worked with him since last September.

Alleman hopes to get a follow-up grant from the National Science Foundation that will enable him to have the bricks made on a large-scale basis at a local company by next fall.

Some sludge has no human waste in it and Alleman also wants to make bricks from that type.

He says he has difficulty acquiring contaminated sludge as opposed to the organic sludge indigenous to nonindustrialized Washington and its suburbs. Although sludge is mostly human waste, any chemicals from laboratories and industrial plants that go down drains also get mixed into the final conglomeration that ends up in treatment plants. Therefore, the more industry in an area, the more contaminated the sludge becomes.

Scientists and environmentalists already know how to put organic sludge, or sludge with very few toxic chemicals in it, to good use as fertilizer and landfill. Contaminated sludge from industrialized areas is much more difficult to dispose of, however, because it is just that -- contaminated.

"We tried to get contaminated sludge from two or three industries in Baltimore, but no one would give us any for fear of what we'd find in it, or who we'd tell after we did analyze it . . . . We've had to go as far away as Rockford, Ill., to get (contaminated) sludge," says Alleman.

"Baltimore still won't give us any of their sludge . . . . We recently made an agreement with a Beltsville company to send us their sludge," he said, but would not reveal the name of the firm.

There may be as-yet undiscovered problems with biobricks, according to Alleman. For example, new toxic gases could be created by heating two chemicals together in a kiln. Also, diseases could be transmitted through the bricks since 30 percent of the material in them comes from humans, some of whom may be diseased.

"There are all sorts of problems that could arise, but only better research will let us know what they are," Alleman stresses.

He hopes part of that research will mean actually building a structure with the bricks next year.

"We may build an outhouse," suggests Alleman.

"I'm extremely interested in these bricks," says Alleman, whose major interest is in waste water treatment. "I guess being the father of s... bricks is not what I really had in mind as my big contribution in life, but if it helps alleviate the problem of sludge then I don't really mind."