Salt Lake City Plan May Turn Sewer Waste To Energy

tuxd00d writes "The question goes something like this: How many toilet flushes does it take to power a light bulb? There's really no answer, but Salt Lake City is exploring a pilot project that would convert sewer waste into energy to run a heating and cooling system in a downtown building, city water department official Jeff Niermeyer said."

Biomass Research at U of MN

[eldavojohn]

From the article,

Attorney John Lear's new offices in the Major George Downey Mansion will be the testing ground for the system. Lear, who specializes in gas and oil law, stumbled upon the idea last year while investigating alternatives to traditional heating and cooling systems.

Does anyone else find it odd that a gas & oil law official is proposing this? I mean, I hope he did his research to make sure that the extra cash spent ensures that this energy is return is worth it. Also, I find it odd that this would be held in a mansion basement and not the local sewage treatment plant where it could eventually done en masse. Aside from watering the lawn, is there a proximity requirement for this particular method of harvesting energy from waste? I wish they would delve more into details but unfortunately all we seem to get is "Simply put, the system would transfer energy from one place to another."

It sounds like it works similar to the biomass ideas I've heard that are constantly arising [com.com]. I would like to see a formal unbiased study done on what process applied to X renewable resources (in this case, waste) is the most efficient in net energy return.

There have been some recent minor [renewablee...access.com] achievements [twincities.com] by a research team at the University of Minnesota (my alma mater) [umn.edu].

I'm not sure if it's related to an effort to introduce it to the public [virginiamn.com]. From that article

The project includes each utility installing a new boiler, fuel handling system and auxiliary equipment to tie into existing turbine generators. The project will use biomass from a tree farm in Aitkin, as well as right of way clearings.

Biomass is organic matter (such as wood) that can be processed into energy for heat, liquid fuels or power generation. Biomass can be combusted directly to produce steam for electricity or it can be converted into a gas to power a turbine.

The boilers will produce 20 megawatts of biomass electricity in Hibbing and 15 megawatts in Virginia.

The two utilities, working jointly as the Laurentian Energy Authority, hold a contract to sell 35 megawatts of biomass power to Xcel Energy.

You might laugh but Biomass is important in Minnesota [mnbiomassexchange.org]--although I realize that the current process isn't as BTU profitable as some Brazilian sugar cane plants, but hopefully they can squeeze more and more useful resources out of what was normally considered waste.

I wonder if it would be possible in the future to engineer plants which when harvested produce an optimal BTU return ... and then make them resistant to the cold cold winters & insanely hot summers of Minnesota. I suppose it wouldn't be safe growing something that's potentially as unstable as impure oil or gasoline though!

Not that new

[kilf]

The main sewage plants for London (Crossness and Beckton), has been burning most of the capital's sewage to make power for several years. According to the link below, they make a little more power than it takes to run the treatment plant. The Crossness station has a really pretty sinusoidal roof.

http://www.portcities.org.uk/london/server/show/Co nNarrative.153/chapterId/3192/Bazalgette-and-Londo ns-sewage.html [portcities.org.uk]

"Just" a heat pump?

[Reverse Gear]

As far as I figure this is just a heat pump, they put lines through sewage that is heating because it is decomposing.
It is a nice idea for sure, I wonder if this hasn't been done already though.

People here in Denmark are having heat pumps installed all over the place and people place these water/air lines all over the place to get air for their heat pump a little hotter than otherwise, burying the lines in the earth below frost depth seems to be a normal choice, but if you anyhow do have a dunghill or something like that why not let the pipes run through there.

Anyhow heat pumps sure is one of the many things that we need to use a lot more in the future, no one technology will be able to replace our use of hydrocarbons, but if we combine all the technologies we have a shot of actually significantly reduce our CO2 emissions.

Trick Question

[Anonymous Coward]

Obviously, the question is in error.

A toilet flush produces a certain amount of energy.

A lightbulb consumes a certain amount of power (assuming a certain average).

You just can't compare the two. You have to integrate power over time first. A better question would be, "how many flushes of the toilet does it take to power a 15W lightbulb for a year?"

Then you can argue that it also depends on what, exactly you are flushing, and its energy content. Maybe some people's poop is more effective than others.

Inaccurate title

[pv2b]

I RTFA, and it seems they're not actually extracting the chemical energy from the sewage -- rather, they're just installing a heat pump to exploit the temperature differential between the sewage and the ground.

Now, using a heat pump might be rather novel in itself -- but extracting energy from sewage is nothing new. We've been doing this in Sweden for quite some time now -- except chemically. Here's a random link with some information about one such installation ... [cardiff.ac.uk]

The resulting biogas is used to replace natural gas in different applications, and we have for quite some time had Bi-Fuel vehicles that can run compressed biogas as well as gasoline, that enjoy certain tax benifits. Also, I seem to remember that a new residential area in Stockholm, Hammarby Sjöstad, is getting a biogas system for heating (and maybe for cooking, I can't remember)...

Either way. Extracting energy from sewage is not a new idea. Extracting heat energy from sewage using a heat pump might be a novel idea, but it's not really any new exciting technology, just a rather clever application of existing technology. Calling it "turning sewer waste to energy" is inaccurate, because the actual sewer waste isn't consumed when you do just, you just cool it down.

more details in Trib article

[willy801]

If you didn't notice this article is a summary from a slightly more detailed article at:

http://www.sltrib.com/search/ci_4602892/ [sltrib.com]

Already done

[StompmotS]

This is already done in atleast one city in Sweden, the heat in the cleaned waste water gets transferred to a district heating system by a heat exchange system. And the then cooled down waste water (just above 0C) is used again as district cooling to a hospital.

The methane is usually used to power the waste water plant itself. Also often used as fuel in busses and cars.

Shit in your veggies...

[Beefslaya]

Columbus, OH had this method in place already. It has been an ongoing project for THE Ohio State University.

The the fact that waste "digestion" produces methane has been known for years.

What got in the way in Columbus was the environmentalists that think that producing our own methane to consume is hazardous to the environment. They stopped the process, and now the solid waste is mixed with mulch and topsoil to create a "Super Fertilizer", which citizens can pay for and use in their landscaping and gardens.

http://www.monolithic.com/gallery/airforms/dystor/ index.html [monolithic.com]

I guess fecal matter in your veggies is more appealing then producing your own form of unlimited energy to these environmentalists.

Maybe they have reinstated the plant, but it wasn't operational when I lived there 2 years ago.