 Robert Hubner
The Agri-Environmental and Bioproducts Engineering Research Group,
headed by Shulin Chen (right), is involved in a number of projects
generally related to water quality. Their work with an experimental
anaerobic digester has generated much interest from dairy farmers,
shellfish farmers, and the governor. See c100.bsyse.wsu.edu/aebe/
Now what about that “technology” that Bishop mentioned? As Bob
Simmons indicated, one of the weaknesses of conventional septic
systems is they don’t sort out the nutrients. New septic technology
can boost nitrogen removal, through natural processes, to 80
percent. But these systems are pricey. When a conventional system
can cost upwards of $10,000, the homeowner understandably draws the
line at just getting the toxic stuff out.
Plus, there are plenty of sources of excess nitrogen other than
human sewage. Animal waste, yard waste, garbage. If it finds its
way into the Sound, it’s more excess nutrient.
The answer that keeps popping up in conversation wherever I go
is the “anaerobic digester.”
There’s nothing new about anaerobic digesters in general.
They’re used throughout the developing world to generate methane.
At its simplest, an anaerobic digester is a sealed container with a
gas valve into which a family can throw its waste, including manure
from animals. Bacteria digest the waste, producing methane, which
can be tapped as cooking fuel or to produce electricity. When the
bacteria are done with their handiwork and the volatile organic
compounds have been stabilized, what’s left is a fine residue that
can then be used as a soil amendment and liquid fertilizer.
“It’s not a magic bullet,” says Shulin Chen, the WSU engineer
who’s been tweaking the technology and consulting with a project in
Mason County. “But it’s a good candidate.”
Once its basic virtues sink in, all sorts of possibilities start
popping up, particularly along the flood-prone Skokomish River
Valley, which empties into Hood Canal. Those possibilities were
clear to Governor Gregoire, who budgeted better than half a million
dollars for the Mason County Conservation District to build a
digester.
Shannon Kirby, an environmental specialist, and Richard Geiger,
an engineer with the conservation district, completed a report in
December regarding the potential for a community digester in Mason
County. One immediately clear use would be to process the thousands
of chum salmon carcasses discarded by the Skokomish tribe after
they harvested the roe. Until recently, the tribe was simply
dumping between 16 and 24 tons of carcasses back into Hood Canal, a
natural enough thing. However, that practice was halted once it
became clear what a major source of nutrient they were adding to
Hood Canal.
The carcasses are currently being composted. Anaerobic digestion
will be better, says Chen. Not only will it circumvent the odor
associated with composting fish, but it would produce methane for
fuel.
The carcass production is seasonal, however, and anaerobic
digesters work best with a steady and continuous flow of feedstock,
just one of the kinks that Chen and Geiger are working on.
Another source of feedstock for the digester is the 1,060 cattle
and horses, 500 poultry, 32 goats, eight llamas, and five pigs that
live in the Skokomish Valley. That’s not a huge livestock
population, but still it means some pretty serious poop, at least
if it washes down river into the Canal. It could mean some serious
methane if it were gathered and digested. Kirby and Geiger envision
gathering that resource as well as, possibly, digesting it, selling
the remains as fertilizer, converting the methane to electricity or
sellable gas, and everybody’s happy.
At least if those byproducts result in sufficient income to pay
for the digester, beyond the governor’s subsidy.
And there’s one of Chen’s primary goals. “We can get a system
working, no problem,” he says. “Our challenge is, how can we reduce
the cost?”
Once that cost is lowered, the digesters will be more attractive
to individual farmers, such as Judy and Darryl Vander Haak of
Whatcom County, who believed enough in the technology to build a
digester on their farm. Their 1,500 dairy cows produce enough
manure to generate electricity to power 180 homes.
So far, theirs is the only digester operating in Washington. But
that should change soon. Chen is testing a digester on the WSU
dairy farm, and Mason County is planning to go ahead with its
digester this summer.
Now—if everyone around the Sound will take Bill Dewey’s advice
and change their lives, the future of the Sound ecosystem looks
downright rosy.
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