[GreenYes] Fw: [epguild] When Kitchen Waste Isn't Wasted- SF Chron]

["Mike Morin" <mikemorin@no.address>]

Subject: [epguild] When Kitchen Waste Isn't Wasted- SF Chron]




URL: 
http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/10/25/ 
FOODSCRAPS.TMP
©2006 San Francisco Chronicle

DAVIS
When kitchen waste isn't wasted
Upscale Bay Area restaurants helping feed machine that turns scraps 
into electricity, vehicle fuel
-Glen Martin, Chronicle Environment Writer
Wednesday, October 25, 2006

Grass-fed beef, organic vegetables and seafood from sustainable 
fisheries have made it possible for Bay Area foodies to make fine 
dining an act of social conscience for quite a while.

Now they can feel virtuous about one more thing: the grub they leave on 
their plate.

That's because scraps from some of the region's trendiest restaurants 
-- Zuni Cafe, Jardiniere, Oliveto and Boulevard, among others -- are 
being enlisted in the quest for renewable energy. Eight tons a week of 
everything that comes back on plates or is rejected by the kitchen will 
be sent to a state-of-the-art digester at UC Davis, where it will be 
transformed into valuable "biogas" -- methane and hydrogen -- and 
fertilizer.

The digester -- an impressive amalgam of vats, piping, cables, 
conveyers and hoppers -- was unveiled Tuesday at a site near the 
campus' wastewater treatment plant. The project is a joint venture 
between the university and a private Davis firm, Onsite Power Systems 
Inc.

The system employs anaerobic bacteria -- microbes that function in 
the absence of oxygen -- to break down waste in large tanks, yielding 
copious volumes of flammable gas.

Ultimately, the plant will handle 8 tons of garbage a day, said its 
designer, Ruihong Zhang, a professor of biological and agricultural 
engineering at UC Davis. Each ton of slops will produce enough gas to 
supply 10 homes, but for now, enthusiasts primarily see it as a way to 
fuel garbage trucks and other commercial vehicles while reducing 
landfill volume. The digesting process converts between 60 and 90 
percent of organic solids to biogas, Zhang said.

Some Bay Area cities -- including San Francisco -- already send 
their food waste to a composting site near Vacaville, where it is 
turned into soil amendment. But in a world increasingly stretched for 
natural resources and overflowing with garbage, that's not enough, said 
Zhang. Her anaerobic digester kicks things up a notch, extracting fuel 
as well as fertilizer from kitchen and yard waste.

Digesters have been around in one form or another for several years, 
but none has proved commercially feasible. Zhang said her plant is 
superior to earlier models because it is far more efficient in terms of 
gas production and cost. It's also the first commercial digester that 
yields both methane and hydrogen in separate stages, she said.

The two gases can be burned together for either electricity generation 
or vehicle fuel. At some future date, Zhang said, the hydrogen will be 
separated for use in hydrogen fuel cells -- devices that have yet to 
be perfected, but are the holy grail for promoters of green-car 
technology.

"Basically we can produce the biogas to many different formulas," said 
Zhang. "This is a system that's ready to go. We've been working on it 
eight years. The technology has been tested and patented. It can be 
scaled up or down depending on need, and it's all based on commercial 
components."

Dave Konwinski, the chief executive officer of Onsite Power Systems, 
said Zhang's invention will allow waste companies to build digesters to 
specifications right at the garbage transfer sites, obviating the time, 
fuel and human power now required to lug refuse from cities to 
landfills.

Konwinski, whose firm has an exclusive commercial contract for the 
digester, said about 20 companies or municipalities already have 
expressed interest in buying the devices.

One of them is Waste Systems Inc., which handles garbage for the city 
of Industry in Los Angeles County. Jeff Duhamel, Waste Systems' 
president, said his company has set aside $400,000 for planning, 
permitting and engineering a Zhang digester.

"We're moving ahead with this," he said. "Ultimately, we figure it'll 
cost us about $2 million."

And that's a bargain, said Duhamel. Industry relies on the same 
landfill -- the nation's largest -- used by the city of Los Angeles.

"The problem is that it'll close in 2013, and at that point we'll have 
to send the garbage by truck or train 200 miles east to a new landfill 
in the desert," he said. "That will cost us $60 to $80 a ton. We think 
this digester will bring our costs down to $30 a ton, when we figure in 
the ancillary benefits of using the gas to power our truck fleet."

The praise got a bit fulsome at Tuesday's event -- not just for 
Zhang's digester, but for the garbage that charges it.

"Maybe we can now look at America as the Saudi Arabia of waste," said 
Rep. Dan Lungren, R-Gold River (Sacramento County). "That can be a 
tremendous opportunity for us. I look forward to the day when we don't 
look at this as an alternative energy source, but as a conventional 
energy source."

Neal Van Alfen, the dean of the UC Davis College of Agricultural and 
Environmental Sciences, said the digester takes advantage of a resource 
modern society generates in abundance.

"We have to switch from the biomass laid down millions of years ago 
(oil, coal and natural gas) to the biomass we're producing today," he 
said.

Certainly, the supply of biogas raw material is abundant. The 
California Integrated Waste Management Board estimates that 22 million 
tons of wet organic waste is produced in the state each year. That 
could be used to generate 895,000 kilograms of hydrogen gas a day -- 
the daily equivalent of 1,363,000 gallons of gasoline.

Some words of caution were raised Tuesday. While hailing Tuesday's 
event as "momentous," Val Tiangco, a representative from the California 
Energy Commission's Public Interest Energy Program, noted the digester 
still has to prove it can go from 8 tons a week to the 25 tons a day 
required for general commercial feasibility.

And a minor glitch in a demonstration of the digester caused a few 
palpitations. When Zhang threw a switch to power a generator to run two 
large fans that, in turn, would inflate wildly gyrating green fabric 
mannequins, there was a brief hum -- then silence.

No biggie, though -- a defective extension cord was discovered, the 
switch was thrown again, and the green figures danced madly in the blue 
October sky. The future of anaerobic garbage digestion seemed secure.

And that's a good thing, say supporters, considering the scant 
alternatives.

"We've made a lot of progress as a society," said Duhamel, "except when 
you look at garbage. For the past 200 years, we've been handling it the 
same way -- burn it or bury it. That can't go on. We have to change."

Page B - 1
URL: 
http://sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/10/25/ 
FOODSCRAPS.TMP
©2006 San Francisco Chronicle

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