New Yorker Mierle Ukeles dreams of the day when the process of waste disposal, from collection to filtration and landfill, will be as beautiful and educational as a medieval cathedral. Japanese artist Kimio Tsuchiya finds the materials of his pensive, poetic art in weekly visits to a giant waste site in Tokyo Bay, euphemistically called "Dream Island." Rolando Pena, a Venezuelan artist who divides his time between Caracas and New York, highlights the link between crude oil and big money by painting oil drums gold.

These three artists and nine others are exhibiting in the indoor and outdoor sites of International Sculpture '90, sponsored by the International Sculpture Center in connection with this week's conference. According to the 12-person jury, they will be leading artists of the 1990s.

Back in the '60s and '70s, the assumption behind most public sculpture programs was that the grim urban environment needed humanizing by art. Sculptors fulfilled this mission by providing colorful relief from the right angles and neutral flat planes of modernist buildings. A big Calder painted fire-engine red with plate steel arches on pointy feet or a curvy, nicely patinaed bronze by Henry Moore filled the bill nicely. Abstract metaphors for birds and bones, Calder's and Moore's works were urban stand-ins for the natural world.

Today's sculptors want a bigger mission than adorning a city plaza. They want no part of "plop art" programs that plop sculptures down in the urban environment without any thought beyond decoration.

Ukeles' "Flow City" is a plan to make a major tourist attraction of New York's central waste transfer station on the Hudson River. On view in the third-floor gallery of 406 Seventh St. NW, her drawings for this ambitious project include a pedestrian walkway, a glass-enclosed bridge suspended over the tipping floor and a wall of videos recording the sounds and images of waste disposal. "It's called 'Flow City' as in 'life flow,' or as in the flow of a river," explains Ukeles. "We have to be able to read these protection systems as holy and beautiful. This is how the earth is being cared for."

An unsalaried artist-in-residence of New York City's Department of Sanitation, she has spent the past 11 years tirelessly trying to reverse the human tendency to shove waste out of sight and mind. In a spirit reminiscent of Gandhi's embrace of the untouchables, she has shaken the hands of all 8,500 New York sanitation workers and thanked them for their work. Says the sculptor, "We create shunned castes of people to deal with our wastes, as if they were the ones who created it. We need to bring their work into the open."

In 1984 Ukeles built a sculpture from sanitation workers' worn-out work gloves, with the literal name of "All Year Long Worn Out Glove Project." In 1985 she conducted "City Machine Dance," a ballet performance by 10 garbage trucks. But "Flow City" is the first piece that reveals the full scope of the artist's ambitions. "Why can't the process of waste disposal become a seedbed of changing the earth," she asks, "the occasion for the greatest designs of our age?"

Recycling has been an important theme of modern art since 1912, when Picasso pasted a scrap of patterned oilcloth on a still-life painting. But artists such as Ukeles and Tsuchiya aren't merely romancing trash. They are serious about it. They rescue it with missionary ardor and transform it into art with the patience of Pygmalion.

"I always use discarded material because it makes me feel the history of a place," Tsuchiya says. "When I use wood from destroyed homes, it seems to be telling me, 'I'm still alive.' It's only the manufactured work, the artificial materials, that seem to be dead."

Tsuchiya lives in Chiba, a village outside Tokyo near the border of a deep forest that is gradually being pushed back by development. His art, he says, grew out of his feelings about this destruction.

"There was this big tree trunk in my studio that is 500 years old," he recalls. "I was staring at this trunk and reflecting on the history of trees, on the history of Japan, on my own place in that history and my birth," which was in 1955, 10 years after the United States dropped the atomic bomb.

One of the pieces he made on this theme was a semblance of the old tree's cross section made entirely out of burnt matches. "I make metaphors for life out of extinct life," the artist explains.

Installed at the northeast corner of the Corcoran Gallery, Tsuchiya's seedpod of shattered Japanese furniture is unfortunately sited -- it suffers the combined roar of New York Avenue traffic and the museum's air-conditioning system. Given its contemplative nature, one should really come upon it in some quiet grove.

The Japanese artist would have liked to make a new piece using trash from the immediate environment, as he did for a 1989 show in Belgium. "During my stay in Belgium and Holland," he commented in a prepared statement, "I came across a heap of iron scrap, logged branches, driftwoods and obsolete woods etc., and in spite of the materials being different, they had a similar fate {as in Japan}. They are debris with a little trace of their old glory."

Tsuchiya objects to the American tendency to associate all Japanese art with Zen. "I live in 1990," he says indignantly. "In today's Japanese life Zen doesn't exist. It has no place in the environment of Tokyo. It's impossible to go back to the old ways, because everything was burned out during the war." However, his art is clearly infused with the traditional Japanese love of nature and its metaphors. So is his favorite poem: "You are only looking forward to seeing the flowers come out, but I wish you to know that at Spring, the grass is growing under the melting snow on the side of the mountain."

Where Tsuchiya's old furniture yearns for resurrection, Pena's golden oilcans have metamorphosed into instruments of destruction. Connected in long cylinders with one end raised, they look like antiaircraft guns or missiles. From their site between the East and West buildings of the National Gallery, they take aim up Constitution Avenue at the Capitol.

Pena is more than a little cagey about his message, though. He has given his installation the neutral title of "Diagonales," and talks engagingly about the beautiful in the everyday.

"You see oil drums all the time," he says. "You see them everywhere. I'm trying to make something so simple, so ordinary, into something extraordinary."

It is only when pressed that Pena talks about the other reasons he has made art about crude oil for the last decade. Back in the 1960s and '70s, he says, he hung out in New York with Andy Warhol, but now he believes that times are getting difficult.

"The planet is getting absolutely polluted, every day," he says. "Everywhere the political corruption is unbearable. The problem with crude oil, the problem with gold, is corruption everywhere. So I make the connection."

It was the spectacular site that gave him the idea for his piece. "When I came to town," he recalls, "we drove around and then I saw the beautiful space in front of the National Gallery. I immediately knew what I wanted to do. I drew it for them."

Pena believes that large-scale public installations using everyday or found materials are the most important form of art right now. "In our era we have to think about recycling," he explains. "I don't have anything against Calder and Henry Moore. They were very honest artists for their time. But I am in the end of the cycle. I am talking about the 21st century."

These are not the only artists in the show whose dreams are fueled by recycled materials. There are 200 blow-dryers in Willie Cole's sculpture at the 406 building. Giancarlo Neri used old office furniture in his untitled installation on view through the windows of Georgetown Markethouse at M and Potomac streets.

Other artists share a concern for the environment. Perhaps the most eloquent work in the exhibition is Shigeo Toya's "The Death of the Forest," placed on the grassy triangle on Pennsylvania Avenue in front of the National Archives. Charred and scarred, a wall of wood seems to be weeping while nearby a single column, charged with druidic energy, suggests the power of the aboriginal tree.

Ukeles suggests that perhaps the art-in-public-places programs, funded by city, state and federal governments, need to be rethought and redirected toward more socially useful projects. In fact, it's already happening, she says.

"My 'Flow City' is being funded by the National Endowment for the Arts' Art in Public Places program," Ukeles says. "It was turned down by the program several times since 1983. There used to be the attitude that what I did wasn't really art. Now they say this is the best public art project they've ever seen."

Vigorously rejecting the arguments of conservatives that the NEA should lose funding, she doesn't find it surprising that Andres Serrano's "Piss Christ," a work of art using human waste, should have been the occasion for the opening attacks on the agency.

Says Ukeles, "The NEA is under attack not because we are in a period of restricted money, but because we're in a time when we've lost our will and our heart. People are afraid of freedom, they're afraid of democracy, they're afraid of multiculturalism. They're afraid of wastes. The entire attack on public funding covers up the desire for repression. The danger of repression is that it's destructive. If you don't pay attention to the power of waste to destroy, if you hide yourself from its effects, it will destroy. We have to open up this entire subject."