RECYCLING: Plants Recovery:Just What The Doctor Ordered

Bill Siuru

Large scale projects such as landfill waste reclamation, municipal and animal waste conversion into biogas fuels and tire recycling have a major impact on cleaning up the environment. Now, smaller scale "niche" technologies currently are being developed to do their share, especially where unique and sometimes very hazardous materials are concerned.

For example, the State University of New York (SUNY) at Stoney Brook's Waste Management Institute is developing techniques to use municipal solid waste (MSW) combustor ash in marine and terrestrial construction materials. Researchers are attempting to create materials that maintain their mechanical properties and structural integrity and that release no organic or inorganic constituents into the environment.

Initially, two artificial reefs constructed from blocks of stabilized combustor ash were placed on Long Island Sound's sea floor. More than a half dozen years later, scientists have detected no change in the reefs' environment. This experiment was followed by a project using MSW combustor ash as an aggregate substitute in cement blocks. Using ash from several resource recovery facilities (RRF) and cement, researchers were able to manufacture blocks that met or exceeded construction performance standards.

More recently, some 350 tons of MSW combustor and bottom ash from Westchester County's RRF, Peekskill, N.Y., were turned into 14,000 stabilized ash blocks. The blocks were used to construct a boathouse on the SUNY campus. The house maintained its structural integrity, and no environmental impact on the surrounding soil, water or air has been detected thus far. Notably, conventional equipment can be used to produce these building materials.

Ports around the country routinely reject large quantities of wooden pallets and packing materials because of possible insect infestations. However, undeterred, ships often will throw the materials overboard as soon as they clear U.S. waters. Inevitably, these materials float back to U.S. shores, introducing dangerous insects, littering beaches and endangering small boats.

The waste wood then must be collected and fumigated before being landfilled. But, while sterilization eliminates possible contamination and littering of shorelines, fumigation is expensive and uses methyl bromide, a dangerous chemical suspected of depleting ozone.

Fiber Fuel International, Savannah, Ga., and two Swedish firms, Nypro and Winbergs, are developing a new method to dispose of the quarantined wood. First, the wood is sterilized using steam. The cleaned material then is processed into a biomass fuel that can be burned in power plant furnaces.

Additionally, Fiber Fuel is identifying wood waste quantities and types at different ports - key information needed to solve the problem. If the project is successful, the technology could be widely adopted at U.S. ports as well as abroad.

In Illinois, the Argonne National Laboratory has developed a technique to stabilize nuclear, hazardous, industrial and electric utility wastes (see chart). The ceramics resulting from their dual stabilization technique can immobilize hazardous heavy metals like lead, cadmium, chromium and mercury, plus radioactive contaminants including uranium and plutonium. The process also can be used to make construction products from benign ash, nonflammable products from waste wood and various ceramic products from mineral wastes.

In addition, Argonne researchers are attacking the problem of storing 100 tons of weapons-grade plutonium as America and the former Soviet Union disassemble nuclear weapons. They are developing a glass material to immobilize the plutonium before burying it in a deep underground repository. The challenge will be to develop a solid waste form that will not break down under the radioactive material's influence, avoid triggering an uncontrolled chain reaction and not be affected by long-term contact with ground water.

So far, a new glass made of tin, zironium and alkali elements, such as sodium shows promise. The tin, zirconium and silicate stabilize the glass structure, the alkali materials dissolve the plutonium, and special neutron absorbers prevent a nuclear reaction. Results to date show that the glass does not break down to form new mineral products and that it firmly retains the plutonium, uranium and neutron absorbers.