Long Islanders used to worry about being buried under tons of garbage. Now, as the Island tries to solve that disposal problem by building garbage-burning incinerators, residents have another worry: the tons of ash produced by burning.
Environmentalists say the ash, containing high concentrations of metals, is unsafe. And incineration solves only part of the disposal problem anyway: each day, for example, Hempstead's incinerator reduces 2,500 tons of garbage to 600 tons of ash, which the town then ships to an upstate New York landfill at a cost of $130 a ton.
But scientists here at the Marine Sciences Research Center of the State University Center at Stony Brook think they have a solution. In a number of experiments, they are studying ways that the ash can be used in construction projects, on roads and in the water.
Someday, they believe, Long Island will be able to use almost all its incinerator ash, an estimated 250,000 tons a year by the mid-1990's.
More than two years ago, researchers at the marine center used several dozen incinerator-ash blocks to build the first of two planned reefs in Conscience Bay off Smithtown on Long Island Sound. The blocks, made by mixing the ash with cement, are still intact, and the scientists say no dangerous substances have seeped into the water or into the tiny micro-organisms that have made their home there.
The ash blocks have become a viable reef, attracting lobsters and sea urchins as well as fish that feed off the small animals on its sides.
The marine center will also take part in a Port Authority study that will use ash to pave part of a road in New Jersey, said J. R. Shubel, the center's dean and director. It is also preparing to build a boathouse on the Stony Brook campus made entirely of ash bricks. And Mr. Shubel said he can foresee a time when ash blocks are used as breakwaters to help stem the erosion of Long Island's Atlantic Ocean shoreline.
With garbage disposal becoming a big problem everywhere, finding uses for ash has become a popular pursuit. Dozens of people recently took part in the second national conference on the topic in Washington. Experts say much of the work, particularly in marine uses, is being done at Stony Brook.
"Rather than give it up as a waste product, why not use it as a resource?" Mr. Shubel said. Environmentalists, however, worry that blocks made of ash will prove to be toxic in later years, when it is too late.
"There's a fundamental difference between disposing and reusing it," said Richard A. Denison, senior scientist at the Environmental Defense Fund, an advocacy group. Using the ash, he said, might mean placing it where people come into contact with it.
"If you're worried about lead in ash in a landfill, you'd better be even more worried about it being in a cement block sold to the public," he said.
Mr. Denison said he supported some of the Stony Brook experiments, particularly those that use the ash blocks underwater, removed from people. But he expressed concern about other uses. In construction projects, he said, there is 'little control over where it goes, who uses it, and how they use it."
"Construction materials are temporary," Mr. Denison said. "Even if the temporary period is decades long, the material ends up in a very different form from when it started."
The Stony Brook researchers say they monitor their experiments closely, checking to see if materials are seeping, or leaching, into the environment. The ash contains the metals that are in the garbage, but in a much more concentrated form, as well as some toxic materials like dioxins.
Vincent T. Breslin, a research assistant professor in oceanography at Stony Brook, said that when ash is mixed with cement to make blocks - usually 15 percent cement, 85 percent ash -the process stabilizes the ash physically and chemically.
"When you form a block with ash you're able to make leaching virtually non-detectable," he said. He keeps a small block made of incinerator ash in his office, and said he is not worried about the possibility of ill effects.
Experts say that the ash is divided into two groups: bottom ash, which makes up the bulk, and fly ash, about 15 percent of the total. The two ashes have different properties, and researchers are much more concerned about fly ash, which is taken from an incinerator's air-pollution control equipment and has higher concentrations of toxic metals. They hope to prove that a mixture of the two, known as combined ash, can be used in ash projects.
"We can confidently say that you can re-use the bottom ash," said Harold Berger, the regional director of the state Department of Environmental Conservation. "There is solid evidence that we can use the combined ash, but the jury is still out on the fly ash."
Mr. Berger said it might be difficult to convince an increasingly skeptical public that the ash is safe. "The problem will be to prove that it's not an environmental problem," he said.
Mr. Shubel said that as raw materials for construction become scarcer -Long Island, for example, is for the first time importing sand for construction -the uses for incinerator ash will become more apparent.
"We could use the ash constructively for 50 years without batting an eyelash," he said.