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Vaporizing Garbage to Create Electricity
CaroKann writes "Geoplasma is planning to build a power plant in St. Lucie County, Florida that will generate electricity by vaporizing landfill trash and sewage treatment plant sludge with plasma arcs. It will be the first plant of its kind in the USA and the largest in the world. The power plant is expected to destroy 3000 tons of garbage, generating about 120 megawatts of electricity per day. The plant will also supply steam to a nearby Tropicana juice plant. The landfill is expected to be depleted in about 18 years. In addition, up to 600 tons of melted, hardened sludge will be produced each day and will be sold for road construction."
"The power plant is expected to destroy 3000 tons of garbage, generating about 120 megawatts of electricity per day."
Watt is a measure of energy per second. That is, power. Saying 120 megawatts of electricity per day is nonsense. I think they meant to just say 120 megawatts.
Doesn't slashdot have editors for this kind of stuff?
Here in the Halton region, which is comprised of some suburbs just West of the Toronto metro, there has been some talk of building one of these plants (although they've tossed around the number $700 million). This is an effort to deal with the reality of garbage, not to mention that reality that Toronto has been giving the entire country a continual black-eye by shipping waste to Michigan (if I were a Michiganer, I'd be pissed to be another regions dumping ground. Even as an Ontarian, the endless row of trash hauling trucks, each leaving a wake of loose garbage, is untenable).
But despite the reality that no one wants to build dumps, and Toronto has been spending millions shipping it to an entirely different country, there are still the head-in-the-sand dreamers who would rather the issue just disappears. A prominent Toronto city bureaucrat, for instance, has poo-poohed the idea, decrying the vile idea of "burning" waste. They'd rather drive it 500 miles in transport trucks to dump it somewhere else.
This has been attempted before. I used to work in the waste industry, and one of my clients had a plan to develop this kind of technology. The problem was that, despite predictions, the waste simply did not burn hot enough. If they've managed to overcome this obstacle, this is going to be huge. The cost-effectiveness still concerns me, but government subsidies can take care of that.
120 megawatts per day? So, after about 8 days, it'll be generating a gigawatt? In a year, will it be producing 43.8 gigawatts?
Probably not.
My first guess was that it's probably generating 120 megawatt-hours per day, or what those of us who know physics would call "5 megawatts".
They say that they'll use about 1/3 of the generated energy, and plan to sell the remainder back to the grid. Electricity is usually worth something like $20-$50 / MWh. If they're selling 3.3MW into the grid, they might be able to get $1600 - $4000 / day from this thing.
However, they also say that they can recoup their $425M investment in 20 years. Assuming a 4% interest rate (municipal borrowing is cheap!), they'd need to pay back a little over $2.5 million per month, or about $85,000 per day.
If the power plant is actually generating 120 megawatts, then they're looking at (80*24) megawatt-hours per day, or $38,400 - $96,000. They're also selling steam and sludge, and I don't know what the current market value of those is. Yes, I know that you pay $60 - $100 / megawatt-hour for your home electric service, but electricity on the bulk market (especially at night) is a lot cheaper.
"Plasma arc" = incinerator. No fancy chemical or nuclear processes happen, they still dump out a huge amount of CO2, just like normal incinerators. Sure, they scrub the exhaust for really harmful chemicals and particles, but they still release a lot of CO2.
It's not possible to have "120 megawatts per day". A watt is a RATE of energy usage (joules per second, in fact). It takes 120 MW to power a million 120W light bulbs -- for 5 seconds, or 5 hours, or a day, or a year -- how long you keep that rate up, has nothing to do with how fast the actual rate is !
Perhaps the article meant "120 megawatt-hours per day", although that would be a very strange unit of measurement (not as bad as Libraries of Congress, though).
Their other products are chump change:
Quarried rock goes for about $3.75/ton. Of the 9000 tons of garbage they burn, they end up with 600 tons of slag, worth about $2000/day.
Steam is worth about $10/1000 lb. The 80000 lbs of steam they'll sell to Tropicana is worth about $800/day.
They don't mention it, but they are probably able to collect tipping fees from the sewage folks and, once this landfill is gone, dumping fees for future garbage.
Still, the bottom line is electricity. If their efficiencies are off or if the market for electricity gets cheap, they may have a hard time amortizing $425 million in debt, even at favorable bond rates. $425 Million at 4.5% over 30 years would require about $2 million/month to service. Their $126K/day income gives them a gross of $3.8 million/month. Enough to service the debt and have about $1.8 million/month for salaries and other recurring costs. It might fly. But if they rack up significant maintenance costs that amount to a significant fraction of their total $425 million plant cost over the 30-year lifetime, it probably won't.