Waste not

Industrial ecologists borrow from nature to create new products

Even if you plant your tomatoes in fertile soil, the vegetables won’t thrive without water. When one thing changes in nature, there are repercussions. The same can be said about industry, according to practitioners of a relatively new field called industrial ecology. In this interdisciplinary field, which is less than 20 years old, industry, like nature, is a system: When one component changes, it can produce far-reaching effects.

Chris Swan has combined two waste products to create a lighter, more flexible building material. © MELODY KO

Consider bottled water. The product affected the oil industry because it takes petroleum-based chemicals to make plastic bottles. When the bottles were discarded, it changed the recycling industry. And the companies that made soft drinks also went in a different direction when they realized it was more lucrative to sell bottled water than other beverages. Consumer habits and spending changed, too, as people became accustomed to buying bottled water instead of turning on the faucet.

Some industrial ecologists try to figure out how industry can emulate nature: Can waste from one industry be another firm’s product? How does the introduction of a new material in an industrial process affect not only that industry, but others connected with it?

Two engineers at Tufts are studying industrial ecology from different perspectives. Stephen Levine, an associate professor of civil and environmental engineering, researches the theory behind industrial ecology, while Chris Swan, an associate professor in the same department, has put theory into practice with his invention of a new product made from two waste products: plastic that cannot be recycled and fly ash.

Similar to the soot created by burning wood in a fireplace, fly ash is a waste by-product of burning coal. (U.S. industries produce between 60 and 70 million tons of fly ash each year.) By combining the two, Swan developed a new material, patented as Synthetic Lightweight Aggregate, which can be used in construction to make building materials lighter and more flexible.

Synthetic Lightweight Aggregate is made from fly ash and plastic. © MELODY KO

Seated in his office, Swan pours out what looks like black pebbles from a glass decanter. But instead of feeling gritty and heavy, they are smooth and lightweight. He and former visiting professor Mohsen Kashi began developing the aggregate a decade ago as they thought about ways to reuse waste to make an eco-friendly product that was technologically and economically feasible.

“Now the idea,” Swan said, “is to take it from laboratory scale to full scale, where someone puts it in a road or uses it in a bridge deck.” While Aggregate is not as strong as sand and gravel, Swan said it has more ductility, meaning it has some give and could be useful, say, for constructing buildings in earthquake-prone areas. Swan said he will continue to refine his product, “thinking not just of applications, but different compositions of plastic and fly ash, and seeing what would work best in different ways.”

Levine was introduced to industrial ecology through Swan’s work. He began considering the economic effects on other industries of pulling fly ash and plastic out of the waste system to make a new product.

“Industrial ecology looks at a broader context,” Levine said, which is why the field has attracted scholars from biology, engineering and economics as well as the social sciences. “It’s looking at pollution, for example, not just by an individual factory, but by entire industrial systems. For example, think about all the pollution generated by the production, use and disposal of an automobile.”

Stephen Levine researches the theory behind industrial ecology. © MELODY KO

Industrial ecology employs a theory called input/output economics, developed by Nobel Prize-winning economist Wasily Leontief. Leontief created a model that describes the flow of goods through an industrial system. Industrial ecologists use the model to determine what a product’s environmental impact is on the world, Levine said.

Levine, too, is working on practical applications in the field. He is involved in an industrial conservation project at Fort Devens, the former military base in Shirley, Mass., that is now a mixed-use development, featuring an industrial park, recreational facilities and homes. A program called EcoStar is helping some of the more than 80 businesses at Devens to adopt conservation practices and encourage one company’s waste to be reborn as another’s raw material. Levine anticipates that the EcoStar project, funded by the Devens Enterprise Commission and Intel Corp., will offer opportunities for Tufts undergraduates to work on senior-year projects or internships.

Marjorie Howard is a senior writer in Tufts’ Office of Publications. She can be reached at marjorie.howard@tufts.edu. This story ran in the November 2007 edition of the Tufts Journal.