June 6, 2007 4:00 AM PDT
Powering cities on landfill waste
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Other processes for converting waste to fuels include ethanol, methane from trash and manure, as well as biodiesel from animal fats. Many of these techniques are being tested to operate at a commercial scale, as part of the clean, or green tech, investment run-up.
Using municipal solid waste as a feedstock hasn't yet taken off because in the past there wasn't much interest in alternative fuels and people underestimated the material handling requirements, Ze-gen's Davis said.
A treatment center in New Bedford will pay Ze-gen a "tipping fee" to take its construction debris, which would otherwise have to be hauled somewhere else. But Davis said the process would be cost-effective even if a waste-to-energy facility operator wasn't paid. It's also conceivable that facilities would have to pay for waste in the future.
The process, if successful, could also qualify for renewable-energy credits or be used to sell carbon offsets, said Flagship Ventures' Matheson.
"Since we're reducing the carbon footprint of incineration and landfill quite dramatically, we think the (facility) should qualify for carbon offsets," he said.
By the end of the year, Ze-gen should have an idea of how its plant is performing, including the quality of the syngas, which varies depending on the process. The modular design of the plant means it can increase production quickly, assuming sufficient capital, and can be used with different types of garbage.
"Given that gasification is proven at a chemical level...it is going to be the next big thing (in waste to energy)," Davis said. "It's just a question of seeing who does it most efficiently."
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19 comments
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Also, how does this lower the carbon foot print. The same amount of carbon in the waste goes into the gas which gets burned and goes into the air, so how is this cleaner that simply burning the waste?
They claim the gasification process is cleaner because you're not creating a lot of carbon dioxide as you would if you just burned the trash. Of course, this type of plant also calls for burning the synthetic gas post gasification to make electricity. But the CEO and prospective investor told me that entire process is cleaner than just incineration.
1. It's possible that this process is more efficient than simple incineration. They're saying that they can produce 38MW of electricity for every 8MW used in the process, which is pretty good. I would guess that standard incinerators are less efficient, though I have no numbers.
2. The gas being burnt is syngas, which burns very cleanly and produces only CO2 as an output. While CO2 gets all the attention for carbon footprints, it's actually not a very strong greenhouse gas as compared to many others. Of particular interest would be methane, that has a solar forcing factor 21 times higher than that of CO2. Burning 1 methane molecule in air to make 1 CO2 molecule (plus 2 H2O) means you've reduced your "carbon foot print" to 1/21 of what it was, even though you still have the same number of carbon molecules.
Probably more important in my mind though is that this process should result in very little air pollution. The big problem with incinerators is not the carbon dioxide they spew but rather the other stuff, like NOx, SOx, carbon monoxide and particulate matter. By gasifying the waste and then burning the syngas you should (at least in theory) have most of your pollutants separated out as solid waste (ash) while the stuff coming out of your smoke stack will be mostly non-polluting CO2 and H2O.
Of course, how well this all works in practice remains to be seen. Also this should in no way supplant the basic reduce, reuse and recycle principles which are almost always much more efficient.
(where I live) in 2004:
www.honolulu.gov/refs/csd/publiccom/honnews04/
plasmaarcrecommendations.htm
consumed to make the molten metal bath and on the contents
of the plant's exhaust and any ungassified waste stream, we
really won't know if it is cleaner. A lot of energy goes into
gassification, so you may not have that much power to sell
because you are using part of the power generated to heat the
molten metal. If you end up with emmisions and minimal power
for sale, it could wind up worse than a high temperature burn
with good furnace air flow control and lots of exhaust scrubbers.
Let's wait for the numbers to come in before we say this is
cleaner and better.
Metal that tried this and failed?
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