June 6, 2007 4:00 AM PDT

Powering cities on landfill waste

Buried in your municipal dump are megawatts of electricity, a resource investors are throwing money and technology at to get.

As interest in unearthing alternative energy sources grows, the technique of converting municipal solid waste into electricity is getting another look and, in some cases, a 21st century makeover.

Start-up Ze-gen is in the process of securing $4.5 million in financing from venture capital firm Flagship Ventures, according to Ze-gen CEO Bill Davis. The money will be used to operate a pilot waste-to-energy facility in New Bedford, Mass., and to fund other projects. The facility is expected to be completed this month.

Using municipal waste to produce energy or reduce pollution is not an unusual practice. Landfill operators siphon off methane gas that is given off by decomposing organic trash. Incinerators burn garbage to produce steam that turns a turbine that makes electricity.

Ze-gen's plant, currently under construction, is an attempt to demonstrate that different technologies--in this case gasification--can be used to convert waste to energy in a cost-effective and less polluting way.

"Even if you don't care about the environmental considerations and just look at it from an economic standpoint, there is a lot of economic potential put into the ground which could be put to use," Davis said.

Davis is one of a wave of entrepreneurs trying to build commercial-scale alternative energy systems. And many entrepreneurs and investors, motivated by concerns about energy security and environmental sustainability, are revisiting old power-generation ideas, including waste-to-energy.

Davis calculates that the 300 million tons of municipal solid waste produced in the U.S. each year could generate tens of thousands of megawatts of power, worth $28 billion.

The process Ze-gen is testing is cleaner than incinerating trash and avoids the production of methane--a potent greenhouse gas--from landfills, said Jim Matheson, a general partner at Flagship Ventures.

"In all the hubbub about energy, clean tech and sustainability more broadly, we think waste has been overlooked both from the dimension of the energy value of the waste and the environmental impact," Matheson said.

Waste-to-energy technologies can be particularly compelling in places like New England and other metropolitan areas that generate a lot of trash, don't have the space for landfills, and have a high energy demand.

Waste not, want not
Ze-gen's New Bedford facility is designed to handle a specific kind of waste stream--the debris from construction and demolition sites, rather than household waste--which will bring in a more uniform input.

Rather than burn the construction debris, which looks like wood mulch once it's processed, it will pass through molten metal at a very high temperature. This gasification process chemically changes the trash to synthetic gas, or syngas, a combination of mostly carbon monoxide and hydrogen.

Waste-to-energy equipment

"We extrude it through a large mechanical feeder with a hydraulic feeder mechanism. Just imagine a tube of toothpaste, pushing a continuous stream below the surface of the (molten metal) bath," Davis explained.

Once captured, the syngas can be burned to power a steam turbine to make electricity. The facility will be able to process 10 to 50 tons of construction debris per day. Initially, the debris will be burned off rather than converted to electricity as the efficiency of the system is tested.

But a facility like this one has the potential to gasify 450 tons of waste and generate 30 megawatts of electricity a day--enough power for roughly 10,000 households--in addition to the 8 megawatts needed to run the plant itself.

There are now 89 waste-to-energy facilities in United States that burn landfill trash to produce power. In total, they create 2,700 megawatts of electricity, enough to power about 2.3 million homes, according to Lori Scozzafava, deputy executive director of the Solid Waste Association of North America. Three more facilities are now being considered, although no gasification plants are operating on a commercial scale, she said.

"There is growing interest in waste-to-energy because of the need for renewable energy, which it is, and because it's sustainable and it's indigenous," Scozzafava said. "It allows waste to be managed closer to where it's produced."

CONTINUED: But is it economical?…
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19 comments

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ass
wouldnt that smell like ass
Posted by mongoose13223 (2 comments )
Reply Link Flag
Quality reporting...
I find the otherwise quality of the c|net news to be degraded by the frequent misuse of English and no editing to catch it. "cites" or sites?
Posted by netman115167 (1 comment )
Reply Link Flag
Only Construction Waste?
Can other forms of waste (paper, plastic, other chemicals) be used in addition to wooden waste at construction sites?

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?
Posted by cmk_78212 (9 comments )
Reply Link Flag
Other waste/ versus incineration
Other forms of waste can be done through this process, according to the CEO. They're initially testing it with construction debris, which includes wood but also other materials.
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.
Posted by mlamonica (330 comments )
Link Flag
Two possibilities jump to mind
There are two things I can think of that might reduce the carbon foot print:

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.
Posted by Hoser McMoose (182 comments )
Link Flag
PLASMA
what exactly is the point of this article? you talk about a company that is converting trash to energy but don't mention how it is doing it? shoddy reporting. it is PLASMA GASIFICATION technology that ATOMIZES the trash into the syngas which is then burned to spin turbines. this is state of the art technology that is only now being used in production environments, and which could one day soon eliminate all of the world's trash and nuclear waste (yes it can burn that too). CNET is about tech, so report about it!
Posted by chris cicc (1 comment )
Reply Link Flag
not yet?
Plasma arc technology wasn't considered viable on O'ahu, Hawaii
(where I live) in 2004:

www.honolulu.gov/refs/csd/publiccom/honnews04/
plasmaarcrecommendations.htm
Posted by sjkx (49 comments )
Link Flag
theoretically cleaner
Until they actually build the plant and get figures on energy
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.
Posted by wylbur (110 comments )
Reply Link Flag
magma molten metal
wasn't there a company in MA in the 90s called Magma Molten
Metal that tried this and failed?
Posted by wylbur (110 comments )
Reply Link Flag
>>>"Powering cities on landfill waste"<<<
A very interesting article indeed; but, it would be good to see all the financial, economic and technical statements; also, the financial, economic and environmental impact on an international scale!
Posted by Commander_Spock (3123 comments )
Reply Link Flag
The toss up "question" is....
... just "how many" (individuals) worldwide can really and truly (all the talking aside) show us some "real" financial, (particularly the economic) and technical numbers/statements in as much as we now live in computer savvy world today!
Posted by Commander_Spock (3123 comments )
Link Flag
So,....
... when is there going to be the worldwide summit on -- "Powering cities on landfill waste"?
Posted by Commander_Spock (3123 comments )
Reply Link Flag
Or,...
... is it that the "big oil companies" are not going to be very happy by these developments worldwide. Huh!
Posted by Commander_Spock (3123 comments )
Link Flag
755
Interesting, cool article, made me chuckle.

<a class="jive-link-external" href="http://www.bestmobiletools.com/popular.html" target="_newWindow">http://www.bestmobiletools.com/popular.html</a>
Posted by shark12er (10 comments )
Reply Link Flag
What about thermophyllic digesters
<a class="jive-link-external" href="http://news.cbsi.com/Microgy+lands+deals+to+help+it+turn+cow+manure+into+natural+gas/2100-11395_3-6135099.html?tag=item" target="_newWindow">http://news.cbsi.com/Microgy+lands+deals+to+help+it+turn+cow+manure+into+natural+gas/2100-11395_3-6135099.html?tag=item</a>
Posted by jamie.p.walsh (288 comments )
Reply Link Flag
Net Carbon producer
The idea that gasification might lead to a net reduction in CO2 or CO emissions is wholly wrong. Almost no construction waste is incinerated, it just sits in the landfill. Biological breakdown of commercial timber is negligible, therefore the CO2/CO foot print of putting it in the landfill is essentially 0. Any emissions above 0 means this is a CO2/CO producing process, regardless of what it's proponents might say.
Posted by feliusrex (48 comments )
Reply Link Flag
Thermal Depolymerization
Close the CO2 loop.

<a class="jive-link-external" href="http://lists.envirolink.org/pipermail/ar-news/Week-of-Mon-20030804/004435.html" target="_newWindow">http://lists.envirolink.org/pipermail/ar-news/Week-of-Mon-20030804/004435.html</a>
Posted by shera89 (19 comments )
Reply Link Flag
There's a group that's building awareness to TVs polluting the world with an online graveyard called JUNKED TV at http://www.junkedtv.com

It's weird how tv's are now popping up on the sidewalks of the world as a common fixture - If you see a junked tv on the side of the road take a pic and email it to them to add it to the campaign.
Posted by petesamuels (2 comments )
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