Saving Our Environment

Movement of waste through a BASIC®system

According to Pollution Engineering magazine, every man, woman and child in the United States produces, on average, 5 lbs of solid waste per day in the form of trash and garbage. That means the average small city of 50,000 people has to dispose of 250,000 lbs of waste every day of the year, over 91 million lbs per year. “Sanitary landfilling . . . has run into a space problem resulting in a crisis point of available land,” Editors Paul Cheremisinoff and Richard Young wrote—in 1975. “Additionally, water pollution problems from leachate . . . cast an ominous cloud over this disposal method. Alternate methods such as composting require careful management and only dispose of a fraction of the solid wastes.”

The problem has only grown worse in the last quarter century. The US population has risen from about 200 million in 1975 to over 280 million today. Our living space is fixed, but at a population growth rate of more than 1% per year, we are adding the equivalent of 66 cities of 50,000 inhabitants to our nation’s rolls every year! The burden of solid waste on our available landfills is staggering.

To cope with this problem, we must recycle our recoverable materials—newsprint, glass, aluminum, and scrap steel, for example—more effectively. And those wastes that are not recyclable—medical waste, rubber, asphalt scrap, plastics, and sludges, for example—must be converted to energy through efficient combustion that will minimize both the residues to be buried in landfills and the degradation byproducts that will otherwise contaminate our atmosphere.

The BASIC® Energy Companies’ patented combustion system does just that. First, it removes moisture from the solid waste before combustion to reduce its ignition temperature. Then, in a three-stage process, the fixed and volatile hydrocarbons in the waste are separated and burned through, leaving minimal ash to be buried and keeping harmful emissions well below federal clean-air standards. Finally, the system generates steam to be used as a source of power.

Infectious waste in red bags, ready for incineration

Take The University of Michigan Hospital in Ann Arbor, for example. The hospital began using a BASIC® system in 1989 to dispose of medical wastes—empty IV bags, gauze, bandages, plastic bottles, needles, containers of pathological waste or body fluids, “red bags” containing infectious wastes, as well as conventional paper waste such as discarded memos and manuals. The incineration system processed 1,200 lbs of waste per hour, 16 hours a day, seven days a week, and generated enough steam to save the institution over $400,000 a year in power costs. In a magazine interview, Director of Plant Operations Don King said: “Instead of sending 100 lbs of compacted waste to a landfill, we send out 3 lbs of ash that has been tested and deemed nonhazardous. We meet stringent state and federal emissions standards, including [those for] dioxins.”

The University Hospital not only filled its landfills much more slowly via the BASIC® system, but also saved substantial money on waste handling costs. “The [system] saves us money here because the alternative is sending this stuff to an offsite facility in 3 ft by 3 ft boxes that cost us over $40 apiece,” said heat recovery foreman Dave Tyler.

The University Hospital was just one small site, but it was doing its job and keeping its environmental impact minimal. Many other sites in the USA and abroad are using similar BASIC® combustion systems to incinerate wastes efficiently. (For a list of representative sites, click on End Use.) Key points to remember: Incineration can (1) reduce waste weight by 80 to 90 percent, (2) reduce waste volume by 95 percent, (3) generate sterile residues, (4) meet all federal clean-air standards, and (5) generate usable energy as well.

Carbon Monoxide
The typical car or truck using your streets and highways emits 500 to 1,000 parts per million (ppm) of carbon monoxide. The typical furnace burning natural gas emits 100 to 150 ppm of carbon monoxide. Picture a cold day in a small city of 50,000 people: about 11,000 cars and trucks flooding the air with this lethal gas throughout the day, and perhaps 8,000 furnaces adding their emissions to the mix. Isn’t it enough to make you ill?

The federal government thinks so, and it has been cracking down on emissions for several years now. The Environmental Protection Agency has set standards for air emissions in industry, not only for carbon monoxide but also for hydrocarbons, nitrogen oxides, hydrogen chloride, sulfur dioxide, lead, mercury, cadmium, and dioxins/furans—all deemed hazardous to human health.

For years, Greenpeace had a “Don’t Burn” policy, because it believed the burning process added some or all of these noxious substances to the air we breathe. And the burning of fuels such as natural gas, gasoline, coal, and kerosene does do this. But incineration—the process of disassociating and thoroughly burning the fixed and volatile components of waste—does not, at least not in amounts the federal government regards as hazardous.

Here’s a look at how BASIC®’s waste-to-energy combustion systems compare with federal standards:

Did You Know?

• That contrary to its usual “Don’t Burn” policy, Greenpeace did give its approval to a BASIC® system used in Canada? The Wainwright Municipal Project in Alberta was originally set up to burn municipal solid waste, but when the MSW wasn’t sufficient to use its full capacity, the Wainwright system began burning whole tires. Later it turned to burning medical waste instead of tires. The local Greenpeace group reviewed and okayed the Wainwright project before it was built.
  

• The BASIC® system in Auckland, NZ disposes of quarantined animal and plant matter

  That a BASIC® system in Alaska was used to incinerate all the combustibles recovered from the Valdez oil spill? The liquid and oil-soaked combustible debris was shipped by truck some 800 miles to the North Slope Borough plant at Prudhoe Bay for burning. Hazardous noncombustibles were shipped to a landfill in Oregon.
  
• That over 1.8 million tons of tires are scrapped every year in the USA? (See below.) A look at the roadsides of some of America’s superhighways would suggest that about that many more are left as blowout debris.
  
• That there are only two EPA-approved hazardous waste landfills in the USA? One is in Alabama, the other in Oregon. The other 48 states are happy to let them have the business.
  
• That a typical 100 million BTU/hr BASIC® system burns about 250 tons (500,000 lbs) per day of typical garbage and generates 6 megawatts/hr of power—enough to handle the electricity needs of 6,000 people for a day?
  
• That some radioactive materials can be destroyed by incineration? Some BASIC® systems are used for this purpose if the radioactive waste is low-level, has a short half-life (e.g., less than one month), and has been stored for a significant portion of its effective life (e.g., six months or more).

Tires as Fuel
In a June 1982 article, Power magazine cited the disposal of scrap tires as a growing national problem. “Industry statistics have shown that more than 180 million tires are scrapped each year in the USA,” the magazine editorialized. “Considering that the average tire weighs in the neighborhood of 20 lbs and has a nominal heating value of 15,000 BTU/hr, the energy conversion potential is obviously worth extracting . . . But exploiting this potential . . . has been a problem.”

Anne Evans of Elm Energy: "We'll use everything but the squeal."

Not any more. BASIC®’s combustion technology has solved the major obstacles to tire burning: the feeding mechanism and the gumminess of rubber waste compounds. Plants using the BASIC® system at Firestone Tire & Rubber Company in Decatur, Illinois and Elm Energy in Wolverhampton, England were designed to not only burn whole tires but to generate power from them as well. Firestone’s plant saved about $1 million per year in fuel costs, and the Wolverhampton plant supplied enough electricity for 25,000 homes.

BASIC® Technology solved the feed problem via its Pulse Hearth®—a suspended brick furnace floor in a step configuration with air jets along the steps. The hearth floor intermittently accelerates and pauses along the length of the radiant combustion chamber to burn in cycles ranging from 20 seconds to several minutes. This shuffles the burning waste through the system in whole rather than shredded form and allows more efficient oxidation to take place through enhanced mixing of the fuel with combustion air. This process also limits the amount of gummy substances on the hearth floor, and the low combustion air velocities reduce the likelihood that fly ash will slag the boiler tubes or escape into the atmosphere. So efficient was the burning process in the Firestone system that no downstream pollution-control devices were required to meet all applicable environmental codes in Illinois.

At Wolverhampton, the Elm Energy plant has been viewed as a model of cleanliness. Under Elm’s contracts with tire suppliers such as Michelin, Pirelli, and Goodyear, every scrap of the tire left after burning, including steel particles and the gunk in the smoke, was reclaimed and sold back to the tire and construction industries. Said Elm’s CEO, Anne Evans, “We’ll use everything but the squeal.”

Asphalt Scrap
Asphalt may be a great material for roofing shingles, coatings, and sealers, but it can be difficult to dispose of. Its combustion characteristics pose material handling problems, and it is difficult to burn in an environmentally sound manner. But Allied Materials Corporation of Stroud, Oklahoma found a way to do it, using a BASIC® combustion system.

Allied operated a manufacturing complex in Stroud that included a refinery, building products, and specialty products. The refinery processed 7,000 barrels per day of crude oil to produce jet and diesel fuels, high-grade lubricating oils, road oils, and naphthas. The asphalt residues from the crude oil distillation process were used by the other divisions to produce asphalt roofing shingles, coatings, and sealers.

Model 7000, used to destroy asphalt scrap

All of these divisions used steam for power. Before adopting the BASIC® system, Allied had two natural gas-fired boilers that between them generated up to 80,000 lb/hr of steam. But as the costs of energy rose, Allied looked for an incineration system that would reduce these costs through waste-heat recovery. Their chief criteria: proven heat recovery efficiency, material handling capabilities for asphalt scrap, and the potential for coburning acidic refinery sludge with a minimal investment in pollution control equipment.

Allied chose BASIC®, and with good reason. Not only did their BASIC® combustion system installed in 1982 meet all of these criteria, but it earned savings of about $1.1 million per year by reducing natural gas usage significantly. Considering that Allied’s cost of the waste-to-energy system was $2 million, it took the company less than two years to recoup its investment.

Allied’s waste-to-energy system used a single BASIC® Model 7000 unit. This standard design had a mass-burning, membrane radiant waterwall furnace equipped with three Pulse Hearth® stoking systems in series. Each one was a solid, refractory-lined hearth that would automatically swing and accelerate slightly forward and upward to move waste through the furnace and agitate it for complete combustion. Two auxiliary gas burners in the main combustion chamber were used during periods of low scrap availability.

Pollution control was built into the design. Low air velocity, temperature, and turbulence in the main combustion chamber, coupled with two reburn tunnels between the furnace and boiler, achieved clean operation without any downstream air pollution control devices.

Ash residues were removed by dump trucks three times a day and deposited in a company-owned landfill nearby. Incineration achieved an 80 percent reduction in weight of the solid waste. [Note: Due to high oil costs in 1985-86, the plant was closed. Three years later, the industrial waste combustion system was changed to a regional medical waste combustion system, with added downstream acid gas controls.]

Sewage Sludge
At its Flint River plant, the Clayton County (Georgia) Water Authority was pelletizing sewage sludge as a means of eliminating waste discharges into the river. Pelletizing produces small granules that are free of harmful bacteria, viruses, and weed seeds. The pellets are suitable for sale as soil conditioner, and for Clayton County this meant their sewage disposal system was generating income to offset costs.

Multiventuri-design wet scrubber for particulate and acid removal

But using a natural-gas and fuel oil-burning incinerator, the process of pelletiziing was both costly and environmentally questionable because of air emissions. With its consultants, the Water Authority came up with the idea of burning some of its own sludge pellets as fuel for the incinerator. The idea was this: If the value of the pellets as an alternative fuel exceeded their sales value as a soil conditioner, the pellets would be burned. If they were worth more when sold as soil conditioner, then natural gas would be burned.

But as far as the Water Authority could determine, no incinerator had ever been used in such an application. The process would require proper handling of the pellets for maximum combustion without causing undue entrainment of particulates in the air stream. In addition, it would have to operate so as to allow the combined incinerator and sludge-drying system to meet air quality standards without a major new investment in higher-powered scrubbers, with their higher utility, maintenance, and operating costs.

After tests of a number of systems, the Water Authority chose the BASIC® design. This design included BASIC®’s patented Pulse Hearth® to move and mix waste particles, and a two-stage reburning process to destroy airborne pollutants. When the BASIC® system was used to burn the dried sludge pellets for fuel, the hot gases dried 2.2 lbs of pellets (5 percent moisture) for every 1 lb of pellets burned. The surplus pellets were sold as fertilizer to a wholesaler in the Florida market.

The combustion system was 75 percent financed by an Environmental Protection Agency (EPA) grant. After it was approved by the EPA and in operation in 1982, another solid waste fuel became available to the Water Authority in abundance: wood chips from the Water Authority’s managed pine plantation, where wastewater effluent was sprayed for final filtration. Rather than enter the wood-hauling business, the Water Authority decided to take advantage of its BASIC® combustion system and burn waste wood as fuel. Since that time, the contaminated wood chips have been the primary feed for the Water Authority’s system, with no changes in design required to accommodate the change in fuel. This change allowed all dried sewage pellets to be sold as fertilizer.

In the process of saving money, Clayton County effectively used its BASIC® combustion system to help keep the environment clean in two different applications— the burning of sewage sludge pellets as an alternative fuel, and the incineration of contaminated wood chips from the pine plantation—all while improving its pollution-retarding performance under the EPA’s clean air standards.