Power Boost

I ncineration has traditionally been the EPA’s least favored approach to dealing with solid waste because of the lost resources and the pollutants emitted out the
stack. But incineration’s cousin, the waste-to-energy (WTE) system, may be redeeming itself because of its best attribute: The energy produced (generally electricity) is a desired commodity used by surrounding communities.

The basic steps in the WTE process that make the critical difference are that the solid waste is burned in a furnace and is channeled into heat tubes of water in a boiler. The high temperatures produced transform the water to steam, the force of which drives a turbine generator, producing electricity. In a clean system, ash particles and harmful chemicals are removed before being emitted as smoke and gases. The heavier ash that falls to the bottom is collected for transport to the landfill, and the remaining gases escape through the stack. It’s this last step that still draws attention from detractors.

ENVIRONMENTAL CONSIDERATIONS. WTE plants produce emissions just like solid waste incinerators do, opponents insist. But WTE defenders say most similarities existed mainly in the early WTE systems and have since been corrected with the passage of the revised Clean Air Act of 1990.

The WTE plant built near Columbus, Ohio, was championed in its early days, even though it was referred to as the "cash-burning plant," says John Remy, director of communication at the Solid Waste Authority of Central Ohio (SWACO), Grove City, Ohio. The plant was designed to burn a combination of coal and the city’s trash. The equipment in the plant was touted as state of the art.

Initially, some components broke down, an inherent by-product of innovation, says Remy. Toward the end of its life, it was denounced particularly because of its emissions. For this, the plant got a bad rap and was closed in 1994. Bringing it up to the new standards was judged to be economically unfeasible. Right now it’s a gutted shell used for storage.

Dr. John H. Skinner, executive director and CEO of the Solid Waste Association of North America (SWANA), Washington, sees fuel generated by WTE plants as one of the cleanest fuels available, provided current standards are met. The mercury and dioxin standards for WTE plants are far more stringent than those for coal-fired plants, he notes. WTE plants are also cleaner, he assures, "than some sources of oil in terms of oil-fired power plants, especially high-sulfur-content oil. The industry over the last 10 years has gone through a major upgrade in terms of installing pollution control equipment as required by the Clean Air Act."

But is WTE a form of recycling, or does it squander potentially recyclable resources? Critics are concerned that if burning collected material were to become more prevalent, there would be less incentive to take the trouble to recycle.

In some states, such as Massachusetts, New Jersey and New York, no new WTE plants will be considered until recycling is thoroughly in place. Currently, 98 WTE systems are operating in 29 states in the U.S., a number that has decreased in the last few years.

Skinner points to statistics to demonstrate that WTE plants are compatible with recycling. "There’s a lot of recycling that goes on in the context of a WTE plant. Metal is often recycled. Quite a few communities have paper recycling programs in conjunction with their WTE plants. The amazing thing, if you look at the statistics on the communities that have WTE plants, is this: The recycling percentage is higher than the national average—35 percent recycling compared to a national average of 30 [percent] to 32 percent."

Burn vs. Bury Costs. WTE plants are considered more costly to operate than typical incinerators. Not only do emission control costs exceed those of coal burning incinerators, but plant capacity is also greater in a WTE than in a coal burning incinerator. For example, it takes 1 ton of garbage compared to ¼ ton of coal to produce the same amount of energy, according to the Energy Information Administration, Washington.

Skinner counters that WTE plants are more economical in the parts of the country where landfill costs tend to be high. He cites the densely populated Northeast as well as Florida, where landfilling is limited because of the high water table. There are not as many further west, he notes, "because landfill prices tend to be lower. The big states for WTEs are Virginia, Florida, New Jersey and New York, where landfill costs are higher. For WTEs, $35 to $40 per ton of waste deposited is typical. In the West, landfill prices are $20 to $25 per ton, so it’s more expensive. But in the East, land disposal [tipping fees] are above $40 per ton, so in those cases it’s competitive."

Some communities and solid waste districts have explored plants that restrict what is burned within them to wood and other "clean" streams that would not present the same emissions problems that occur when plastics and chemicals are part of the incoming material stream.

According to Skinner, "Wood-only plants are very different. Because garbage is such a mixture of heterogeneous material, the grates that are used are specially designed to provide airflow and turbulence in the combustion process. A plant that just burns wood chips would be a much simpler furnace, not anywhere as complex as a WTE combuster."

Nevertheless, even plants that burn only this biomass material have adversaries. Significant opposition was generated in a North Carolina community where such a facility was proposed. However, one such facility in Kenansvillle, N.C., operated by Green Power Energy of N.C. and permitted to burn coal, wood and tire-derived fuel, seems to have been accepted by the community.

But in other communities, WTE plants have encountered opposition because people think of them as incinerators that are burning regular trash.

Rick Trautman is operations manager for RBS Enterprises, West Chester, Pa., which supplies containers to collect and transport C&D materials, such as roofing shingles, gypsum drywall, carpet and wood, from construction and demolition sites to recycling centers and transfer stations for further sorting and eventual shipment to a landfill or a consuming plant for recyclables. "We’ve been trying for six years to open a plant in New Castle County [Delaware]. The state wants it, but there are people protesting against it because they think it will be an incinerator," Trautman comments. "They take the wood and tires that are chipped up and they use it as pellets to fuel the plant. It uses those pellets as a fuel source instead of coal, diesel, air or water to turn turbines. It uses the heat to turn turbines. It’s the same thing as buying wood pellets at a hardware store for a wood stove," he remarks. "Green Power is what it says it is, using recycled products," he states.

"Residents of New Castle County don’t want it. The city of Wilmington wants it in the worst way for the jobs it will produce, plus it diverts materials from the landfill," Trautman continues. He says landfill managers can extend the lives of their landfills by diverting construction materials, which "take up air space and valuable land space, whereas regular trash is easily compacted and weighs much more." He adds, "When we set up a recycling center, 99 percent of the load is recycled: Wood is burned and recycled for fuel; the drywall is pulled out and reused; cardboard, plastic, metal are all reused. Farmers use drywall and pulp for fertilization; shingles are reused for roadbase or new shingles."

HOPES FOR THE FUTURE. Taylor Recycling of Montgomery, N.Y., has an entirely different waste-to-energy process that it has developed. Taylor Recycling processes solid waste, mainly from construction and demolition sites, creating several value-added products. The company operated screens that played a major role in sifting through the 9/11 World Trade Center debris, an activity that inspired Taylor to develop degrees of separation that had never been accomplished before.

"We can create an automated process to completely deconstruct your trash and separate it out into the biomass fraction, the inorganic fraction, the synthetic fraction that is appropriate for energy (for the most part) and also the household hazardous waste fraction, which shouldn’t go into an energy process," explains Tom Kacandes, vice-president of business development with Taylor Recycling.

"What comes out of the back end of our system is ground material that has been prescreened," he continues. "Recyclables have been removed from the incoming material," he says, noting that metal and concrete have a greater value as recyclables beyond energy units. "Wallboard has a lot of sulfur that is very bad for an energy process because it makes sulfur dioxide. Otherwise, biomass has no sulfur, so it’s a very clean fuel stock," Kacandes remarks.

But even the materials set aside for waste-to-energy purposes will not be burned in a furnace. "Instead of burning it, the biomass gasification process that Taylor is going to be deploying literally pours hot sand over ground-up materials that are no bigger than a softball. The sand pours over that surface area, rapidly heats that biomass and converts it to a gas that is substitutable for natural gas," says Kacandes.

"It has about half the energy density of natural gas, and that’s close enough for it to be substitutable or even mixable with natural gas directly at the point of being then burned in a boiler or turbine that’s going to make heat or electricity," he says. "Because the product that comes from the waste is a gas, not just steam or heat, it can be used in more efficient combustion processes, like combustion turbines or reciprocating engines."

LESS FILLING. One advantage of WTE plants that is not contested is waste reduction. The amount of waste that has to be eventually disposed of is significantly less, with a volume reduction of 90 percent and a weight reduction of 80 percent, Skinner says.

And that waste reduction is immediate, with destruction occurring in seconds as opposed to the hundreds of years in a landfill. Kevin Trytek of Regional Waste Systems in Portland, Maine, says that at his agency’s facility, "once buried, the ash turns to a hard concrete, and the heavy metals, like lead and cadmium, are bound within the ash. A lot of ash testing is done to make sure it meets its leachability characteristics."

If energy prices escalate, the WTE plant might be seen as a welcome alternative. In communities that view WTE plants as mere incinerators, that would not be the case. In Columbus, where residents have experienced the high cost of operating a WTE in its early days, opposition remains.

Even today, following the changes in pollution control laws, these plants have become more expensive to operate than originally envisioned. But municipal waste itself is cheaper to burn than coal. As William Turley, executive director of the Construction Materials Recycling Association, Lisle, Ill., points out, with construction and demolition materials, "You get your infeed fuel for free or for a very low price. You can compete very handsomely on the power market. And recovering the Btu value of it is a tremendous step above sending it to a landfill."