Dredging for bricks

Scientists at Brookhaven National Laboratory have helped develop a new technology that converts material dredged from harbours into a substance that can be made into construction-grade cement.

Scientists at the US Department of Energy’s Brookhaven National Laboratory have helped develop a new technology that converts material dredged from the bottoms of harbours and waterways into a substance that can be made into construction-grade cement.

The technology, called Cement-Lock, was developed in collaboration with the US Environmental Protection Agency (EPA), the State of New Jersey, and other government and public groups.

“This technology will greatly help to increase the health of many US harbours and waterways, such as the Port of New York and New Jersey,” said Keith Jones, an environmental scientist at Brookhaven who took part in Cement-Lock’s development. “These waterways are contaminated by metals and pollutants from many human activities, such as sewer overflow systems and discharges from industrial operations.”

To ensure that the port can continue to service large container ships, which need deep water, it must be dredged regularly, Jones explained. But because the dredged material is contaminated, there are very strict restrictions on where and how it can be disposed of.

“This is one of several promising technologies that have the power to solve the problem of dredged material,” said EPA Regional Administrator Jane M. Kenny. “It enables us to treat contaminated material and use it beneficially, instead of adding tons of material to landfills that are already short on space.”

According to Eric Stern, the EPA Regional Contaminated Sediment Program Manager, “Sediment decontamination is a component of an overall dredged material/contaminated sediment management strategy. What sets this program apart from typical remediation is that beneficial use products – cement, lightweight aggregates, bricks, and soils — are the end result.”

The Gas Technology Institute (GTI)) in Des Plaines, Illinois is now carrying out a large-scale demonstration of the Cement-Lock process with a specially constructed 10-foot diameter by 30-foot long rotary kiln melter.

In the process, dredged material and modifying minerals are loaded into the kiln and heated to between 2,400 and 2,600 degrees Fahrenheit, creating a molten material. The high temperature causes some contaminants in the material to break down into environmentally safe components that are vented to the atmosphere, while the contaminants that do not break down are incorporated into the melt.

The resulting treated material, called “Ecomelt,” is then ground to a powder and blended with cement. The Ecomelt takes part in the hardening process of concrete, which is a mixture of cement, sand, gravel, and water. Further, Ecomelt is said to reduce the quantity of other raw materials that are typically used in cement manufacturing, such as shale.

After the testing phase, which will treat 400 cubic yards of dredged material from New Jersey’s upper Newark Bay, EPA and the New Jersey Department of Transportation (NJDOT) will work with GTI to develop a commercial kiln that can treat up to 500,000 cubic yards of sediment per year.