Saturday, July 12, 2008

What to do with all that trash?

Vaporize it!

A Florida county has grand plans to ditch its dump, generate electricity and help build roads -- all by vaporizing garbage at temperatures hotter than parts of the sun.

The $425 million facility expected to be built in St. Lucie County will use lightning-like plasma arcs to turn trash into gas and rock-like material. It will be the first such plant in the nation operating on such a massive scale and the largest in the world.

Supporters say the process is cleaner than traditional trash incineration, though skeptics question whether the technology can meet the lofty expectations.

The 100,000-square-foot plant, slated to be operational in two years, is expected to vaporize 3,000 tons of garbage a day. County officials estimate their entire landfill -- 4.3 million tons of trash collected since 1978 -- will be gone in 18 years.

As of yet, the facility hasn't yet been built, despite this project's declaration two years ago that it would be built within two years. Hey, that's government for you. Does that mean it's pie-in-the-sky science fiction? Nope. This technology actually isn't brand new and is in operation in other countries.

This article from Popular Science gives an in-depth look at an American company hoping to convince cities to use its plasma jet waste disposal technology.

Called plasma gasification, it works a little like the big bang, only backward (you get nothing from something). Inside a sealed vessel made of stainless steel and filled with a stable gas—either pure nitrogen or, as in this case, ordinary air—a 650-volt current passing between two electrodes rips electrons from the air, converting the gas into plasma. Current flows continuously through this newly formed plasma, creating a field of extremely intense energy very much like lightning. The radiant energy of the plasma arc is so powerful, it disintegrates trash into its constituent elements by tearing apart molecular bonds. The system is capable of breaking down pretty much anything except nuclear waste, the isotopes of which are indestructible. The only by-products are an obsidian-like glass used as a raw material for numerous applications, including bathroom tiles and high-strength asphalt, and a synthesis gas, or “syngas”—a mixture of primarily hydrogen and carbon monoxide that can be converted into a variety of marketable fuels, including ethanol, natural gas and hydrogen.

Perhaps the most amazing part of the process is that it’s self-sustaining. Just like your toaster, Startech’s Plasma Converter draws its power from the electrical grid to get started. The initial voltage is about equal to the zap from a police stun gun. But once the cycle is under way, the 2,200˚F syngas is fed into a cooling system, generating steam that drives turbines to produce electricity. About two thirds of the power is siphoned off to run the converter; the rest can be used on-site for heating or electricity, or sold back to the utility grid. “Even a blackout would not stop the operation of the facility,” Longo says.

It all sounds far too good to be true. But the technology works. Over the past decade, half a dozen companies have been developing plasma technology to turn garbage into energy. “The best renewable energy is the one we complain about the most: municipal solid waste,” says Louis Circeo, the director of plasma research at the Georgia Institute of Technology. “It will prove cheaper to take garbage to a plasma plant than it is to dump it on a landfill.” A Startech machine that costs roughly $250 million could handle 2,000 tons of waste daily, approximately what a city of a million people amasses in that time span. Large municipalities typically haul their trash to landfills, where the operator charges a “tipping fee” to dump the waste. The national average is $35 a ton, although the cost can be more than twice that in the Northeast (where land is scarce, tipping fees are higher). And the tipping fee a city pays doesn’t include the price of trucking the garbage often hundreds of miles to a landfill or the cost of capturing leaky methane—a greenhouse gas—from the decomposing waste. In a city with an average tipping fee, a $250-million converter could pay for itself in about 10 years, and that’s without factoring in the money made from selling the excess electricity and syngas. After that break-even point, it’s pure profit.

Someday very soon, cities might actually make money from garbage.

Of course there are naysayers and skeptics. I'm hoping they'll be proven wrong and we can get this technology under way very soon. Not only would it make trash into money, it would mean that we could actually do something with all that plastic in the landfills (styrofoam!!) and cities wouldn't have to deal with all the problems of trash. And of course, the energy bonus is a must in these times where energy is in such high demand.

In the meanwhile, some cities are trying out other options to make the best of what they've got. Dallas is implementing an advanced method to compost all the old trash in the landfill.

The city is currently preparing the first “cell” of the landfill for use in the project.

At 30 acres, the cell is little more than a giant trench with rising bluffs that overlook downtown.

Come October, the city will bury the first stretch of pipeline in the cell.

The pipes, which will be stacked in layers of seven across the cell, are the key to a system designed to feed microorganisms that produce gas, largely methane and carbon dioxide, as a byproduct.

One series of pipes will pump in water and landfill liquid, known as leachate. The moisture will saturate the trash, making a better food source for the naturally occurring organisms. As gas is produced, a second series of pipes will extract it using vacuum pressure. It will then be sent to an on-site processing plant where carbon dioxide will be separated from methane. The methane then will be transferred to an Atmos Energy pipeline.

“The theory behind this is nothing more than a big compost pile,” Mr. Smith said.

Only, you can’t turn a landfill over like you can a compost pile in the backyard. Instead, water has to leach slowly through the trash.

As it does so, “the microbes go crazy,” Mr. Smith said.

Methane gas, the main component of natural gas, is produced at two to three times or more the rate that it would be in a traditional landfill.

As it stands, McCommas already captures about 5.6 million cubic feet of methane a day, which is piped to an on-site plant operated by the independent company, Dallas Clean Energy. Some of the city’s estimates show that by 2012, output could exceed 20 million cubic feet per day.

That will not only generate more fuel for use in and around Dallas, it will add a pot of revenue to the city coffers of $30,000 to $50,000 a month, officials estimate.

Very cool.


Kelly Bliss said...

Composting the landfill may give gas for power, but it also pollutes the ground water. The water that is pumped in to encourage the microbes filters down into our ground water, bringing all the toxic chemicals with it!

Nat-Wu said...

Engineers already know that seepage can contaminate groundwater, and they have to prevent that from happening when it rains anyway. That's why the landfill is already sealed on the bottom and sides. Unless the seal just doesn't work well enough, I can't see how that would be a problem.