Processing Garbage Into Dollars

AMERICANS discard more garbage per person (about 2,000 pounds a year) than people from any other nation. But Australians come in a close second. So, it is not surprising a Brisbane company has developed what may be one a significant breakthrough in waste disposal: a factory that turns garbage into nontoxic building material.

If the Neutralysis Industries process lives up to its potential, the days of landfills and mass incinerators worldwide could be numbered. The process can also dispose of sewage and reclaim old landfill sites, says Neutralysis general manager Peter Thorley.

``We think this is the breakthrough the world has been waiting for,'' Mr. Thorley boasts. ``We expect the first full-scale commercial plant to be built within two years.'' Four Australian cities are looking at building Neutralysis plants. After unveiling the process at recent trade fairs in the US and Europe, Neutralysis has begun negotiating licensing agreements with companies in the US, Canada, Britain, the Netherlands, Norway, and Sweden. Patents are held or pending in 30 countries. After $6 million and five years of research, a 20-ton-a-day pilot plant now chugs away in a residential-industrial section of Brisbane.

At one end, the plant swallows a mix of one ton of ordinary household waste, one ton of clay, and 300 liters of water (or sewage). Magnets suck ferrous metals out of the garbage. Then, the brew is minced, extruded into marble-sized pellets and cooked at 1,200 degrees C. in large, rotating kilns looking like giant rusty tennis ball cans. At the other end, tiny glowing pebbles spit out to cool.

The resulting terra-cotta gravel is called Neutralite. It is a lightweight material that can be added to cement to produce blocks one-third lighter than normal cement blocks. Similar cement-fillers known as ``lightweight aggregates'' are already used to construct high-rise office buildings and bridges.

``Neutralite has enormous potential,'' says Mick Ryan of W.G. Ryan & Associates, a concrete technology consultant. ``Initial tests show it's as strong as ordinary concrete blocks, with good acoustic and thermal properties. But we need another six to 12 months of testing.'' But is it safe? Similar baked-garbage bricks have leached pollutants.

``Our preliminary investigations suggest a very environmentally friendly product. Leachates coming out were well, well below US Environmental Protection Agency [EPA] guidelines,'' says John Ware at Griffith University.

Gas emissions and fly ash are also potentially environmentally damaging byproducts of the process. But both can be controlled, Mr. Ware says. ``While I'm not prepared to say the emissions are totally safe, I can say the technology is available to deal with the gases. And the emissions from this process are much lower and easier to manage than emissions from mass-burn incinerators.''

Fly-ash production is also much lower than with current urban incinerators. Conventional incinerators leave 10 times as much fly ash as the Neutralysis process, Ware estimates. Under revised US EPA guidelines, heavy-metal laden fly ash is considered hazardous waste that increases disposal costs.

Recently, managers from a large local disposal company dropped in to look over the Neutralysis pilot plant. Moments later, Thorley says with a smile, ``The big boys are starting to worry.'' Neutralysis is among three bidders to handle Brisbane's waste disposal over the next 15 to 20 years. The city of 1 million people generates about 2,000 tons of garbage a day. The Neutralysis bid will propose building four 500 ton-a-day plants (possibly on old landfill sites) at a cost of US$25 million to $30 million each.

Although the process is relatively untried, the technology is all off-the-shelf. Thorley ticks off the Neutralysis advantages: No need for landfills with leachates seeping into the groundwater; fewer air pollutants due to higher temperature burning than mass incinerators; low transportation costs because multiple plants can be built close to the city. Thorley also calculates construction costs for four plants will be less than one large mass-burn incinerator.

The economics of running Neutralysis plants are appealing. Operators could reap income from five different sources: Garbage disposal fees, Neutralite sales, scrap-metal sales, sewage disposal fees, and sales of electricity or steam generated by excess heat.

Except for an initial blast of gas or oil to start the kilns, the process is energy self-sufficient. The methane gas released by the garbage fuels the kiln fires.

One possible shortcoming is that while there is a shortage of this material now, 500 tons of garbage a day transformed into Neutralite pebbles could eventually flood the lightweight aggregate market. Still, piles of fairly inert rocks are presumably preferrable to piles of stinking garbage.

``In the future, when this company has ironed out the problems of dealing with urban waste in an environmentally sound way, this process has the potential for dealing with a large number of toxic wastes,'' Ware notes.