All posts in the topic Minneapolis: getting power from our poop (Short link)
Summary
- There are 7 posts — by 5 authors — in this topic.
- Latest post made by Bill Kahn (D) at Jul 18 05:26 UTC
I have been thinking a lot about energy use and sustainability recently, and
some of it has to do with what happens after we flush our toilets.
As I understand, about 80% of Minneapolis's septic sewage goes for processing
to the Pig's Eye sewage treatment plant in St Paul. Surfing around on the
internet, I determined that there is all sorts of settling and sludge removal
that takes place. Part of the process involves burning the sludge in a big
incinerator, which eventually produces both heat and electricity (apparently
the Met Council makes over a million dollars a year on this electricity).
So I cannot find any reference at all to methane gas, which is used as a
substitute for natural gas and can be used in mixtures with diesel fuel or to
produce electricity. I came across a news article (which I cannot now find)
that indicated that San Diego has installed an anaerobic digester for their
sewage. The project cost $1.6 million (as I remember), but it produced an
additional $320,000 every year of operation. Which is a VERY fast payback for
any sustainable energy project.
I have already read enough about this issue that I know that methane digesters
cannot eliminate the odors associated with sewage. And I realize that the
methane digesters do nothing to eliminate the toxic metals that end up in
sewage sludge and that can cause air pollution problems during incineration or
when the sludge is used as a fertilizer. But these problems are current
problems as well, with or without a methane digester.
One article I read indicated that Germany used captured methane gas during
World War II and that several other post-war European companies did as well,
until petroleum became cheap and available again.
To my simple way of thinking, methane makes a very complimentary energy source
when we think about obtaining our electricity with wind. Wind, of course,
comes and goes. Thus many argue that big coal-fired plants are necessary to
maintain a baseline. Gas-powered plants can be brought on-line very quickly,
but natural gas is getting hugely expensive since we are apparently a couple of
years beyond peak natural gas.
But what if we hooked up digesters to all our sewage systems? What if we
hooked digesters up to feed lots and even city compost piles? We lose none of
the fertilizing nutrients, but we could capture and store and use the methane
gas to run electric turbines much as we now use natural gas.
So now I have to admit that I am a kindergarten teacher, not an engineer or a
scientist or even citizen who has spent much of my life exploring these issues.
I am very eager to have others provide information and criticism on these
suggestions.
Here's one way of saying the question simply: Would it be possible for
Minneapolis to become completely sustainable in its electricity use by
contracting wind farms for most of our electricity needs and supplementing with
our own methane-fueled plants when the wind dies down?
Comments? Flaws in my thinking? Stories you heard about from other cities? I
am quite eager to get some feedback on this subject.
> Here's one way of saying the question simply: Would it be possible for
Minneapolis to become
> completely sustainable in its electricity use by contracting wind farms for
most of our electricity
> needs and supplementing with our own methane-fueled plants when the wind dies
down?
>
> Comments? Flaws in my thinking? Stories you heard about from other cities?
I am quite
> eager to get some feedback on this subject.
I'm skeptical that just wind and waste-methane would be enough to
manage all our needs, but it would certainly get us closer. Combine
in solar, a bit of hydro, fuel-from-trash, and possibly some bio-mass
fuel and I think that, combined with a citywide effort towards
reasonable conservation, we could manage to do pretty well.
I think this is exactly the sort of thinking we need.
I'm concerned that we're already a bit too late to have the spare
resources to invest in building the infrastructure we need, but the
longer we wait, the worse it is going to get. Honestly, I've been
pleasantly surprised at how quickly thinking seems to be shifting. I
was just reading that many metro areas are suddenly finding that their
public transit can't keep up with demand - those who predicted this
even a few years ago were often ridiculed.
Anyway, I hope we can get it in gear while we still have some breathing room.
Thanks!
- phaedrus (jason.goray), 3-6, minneapolis, mn, usa, earth.
Another problem is that "poop" only represents a fairly small amount of the
material in the sanitary sewer system. The majority of liquid is going to be
"grey water" from showers, clothes washers, dish washers, and just running the
sink while you brush your teeth. Add in ground water incursion and overflow
from storm sewers and the sewage ends up pretty watered down. Whether there is
enough food left for a digester would be the operative question. Plus whatever
hazardous waste that finds its way in and the impact that would have on the
positive microbes.
Also, unless you're planning on completely repiping the city's sewer system,
the location of this plant will be very limited to the existing gravity sewer
trunk lines, so basically just a couple spots, and potential for major NIMBY
problems.
John McClellan
Keewaydin
This discussion got me wondering about our current electricity sources, and
I was not able to find this info with Google.
Does anyone know currently and accurately what percentages of our
electricity comes from what sources - either in Minneapolis or state wide?
(Coal, nuclear, hydro, wind, biomass, natural gas, what else?) And what our
progress is toward tge 25% by 2025 renewable standard?
Thank you!
Nikki Carlson
Linden HIlls
Nikki, Nikki, Nikki. No googling some things without a clear notion of what you're looking for, I guess. You get the information with many of your power bills, so look at your power utility company's site. It is going to vary a great deal from one company or cooperative to the next (check out the PUC for a complete list), because they all have different priorities. Nikki, like me and most on this forum, probably gets electric power from Xcel, but there are dozens of other providers in the state, and if you're way north or way south you might know folks who get their juice from one of the cooperative members of Great River Energy, or perhaps a municipal utility further out. We'll settle on a look at Xcel Energy's website then: HTTP://www.xcelenergy.com Put your cursor over the "Company" pull down menu and click on "Power Generation" and you'll get a chart breaking it down for this electric utility. I guess most in Minneapolis are supplied by Xcel. You can also look at or download Xcel's plan to reach the 30% by 2020 (according to Xcel's site; don't know about Nikki's target; just heard Al Gore say we could and should have 100% in 10 years) in the same area of the site. I was really bummed when I learned that Met. Council is incinerating most of the poop at Pigs Eye (check out http://tinyurl.com/25tlvl), and Xcel is paying them for this, presumably getting credit for progress towards the renewable plan targets. The Met Council used to use anaerobic digestion for most of the solids, but the complaints about the stink moved them to settle out the solids and treat the water, and then burn the solids. It seems like they could combine a sealed AD process for both poop and the suitable part of municipal solid waste for a much cleaner result, right now they process and burn it all, releasing all sorts of emissions that they don't have to. The NIMBYs win and we all lose until we really think about this stuff and get a better handle on poop and other "waste." Many of us are hopeful that biogas opportunities will lead to supplying methane rich natural gas through existing pipelines to those who need it, perhaps even to supply a great deal of the thermal energy needed to run the Rock-Tenn paper mill recycling operations just a few blocks into St. Paul from me (they're looking closely at AE); luckily, Xcel is interested in moving biogas this way, so it is a possibility in their distribution area, but it would be nice to have laws that nudged utilities and others in the right direction. A close look at the refuse derived fuel industry and some of the other "green" things that are done by energy producing concerns in our state and you start to lose hope for any kind of sustainable life that isn't "solitary, poor, nasty, brutish, and short," i.e., our natural Hobbesian state avoided only through using the highly evolved brains were born with (many of us, anyway).
Thank you, Bill. I checked it out. There is a chart that shows "generating
capacity" in megawatts for "generating facilities" that are "owned by Xcel."
I don't think these are total numbers that can be translated to percentages
of energy actually used.
The natural gas capacity looks like about 31% (of 15,799 MW total), but I
read somewhere the actual use is more like 1%. Also, the coal number here is
about 52%, but everywhere it is reported to be more like 70%. Then while it
says generating capacity for wind is 27 "MW", there is a footnote that says
they purchased 1,296 "megawatts" of wind. I think Xcel purchases something
like 15-25% of its energy, so I don't think this data gets at total
percentages of sources for our electricity. While now my brain has more
data, I feel less informed. Any more advice? I could use it. Also, do you
know the terms "facilities" and "units." What's the difference? Help!
Nikki Carlson
Floundering Google Novice
Linden HIlls
Don't know what to say, Nikki. The generating capacity of different facilities by the fuels they use is a pretty good way to determine the mix. I mentioned the brochure that comes with your bill a few times a year and that has the percentages you're asking about and come pretty close to yourself from looking at capacities; I don't know where your other figures are coming from. Find a pdf of a recent Xcel environmental brochure here: http://tinyurl.com/6oq2yn As I said before, the Commerce Department tracks a lot of energy statistics. See http://tinyurl.com/e5v32 for their energy info center and knock yourself out. There's a whole lot of information from DOE, as well; you just have to go there and spend the time to find what you're looking for.