Sep 11 2008 3:55pm

What a Load of Crap: San Antonio’s New Energy Solution

The good people of the city of San Antonio, Texas produce 140,000 tons of sewage—or “biosolids,” as the sewage industry so delicately puts it—on an annual basis. What to do with all that...stuff? San Antonio has a good idea: Make fuel out of it. San Antonio has contracted with Massachusetts energy company Ameresco to use all those biosolids to create natural gas. San Antonio and Ameresco will use some of it to power its sewage systems, and the surplus will be sold for a profit.

How much natural gas can come out of San Antonio's sewers?

“Treating these biosolids generates an average of 1.5 million cubic feet of gas a day,” San Antonio Water System chief operating officer Steve Clouse said. “That's enough gas to fill seven commercial blimps or 1,250 tanker trucks each day.”

“We have for many years wanted to find a beneficial use for these waste gases,” Clouse said. “Most of that gas is currently burned off using flares.”

San Antonio apparently already recycles the water from its sewage from irrigation and the biosolids as fertilizers for local farms, so this is just another step in reclaiming everything reclaimable from what San Antonians flush down their pipes on a daily basis. And while it’s requiring every single ounce of my will not to make various fart and crap jokes, I think this is a fine idea. Energy is energy, wherever it comes from, and burning off all that natural gas rather than putting it to profitable use (in more one sense of the term) is silly and wasteful. It would be nice if other municipalities picked up on this idea as well. There’s a lot of “biosolids” and sewage out there. Might as well get something useful out of it. Wasting energy is a crappy thing to do.

Sorry, I couldn't help it. Please don't hit me.

(Image nicked from here and used under Creative Commons license.)

Matthew Jarpe
1. mjarpe
I remember my junior high school teacher telling us about this back in the late 70's. I don't know if it was economicaly or technically feasible back then, but I can only imagine how many sewage treatment plants have been built in 30 years that could have harvested this energy source. How stupid are we going to feel if we find out we flushed away our planet's future?
Eric Tolle
2. ErictheTolle
I think this is a great idea; every time I've seen a picture of a landfill converted to a golf course with pipes to release the natural gas I wondered why it wasn't saved and used.
James Campbell
3. semaj51
The question is, how much will it cost to convert the present sewage system to trap this gas, and will it be economically feasible?
4. nutmeag
Wow, how is it that I live in SA and this is the first I've heard about it--way to get on the news, Tor! Interesting idea. SA is actually doing a good job of trying to do its part in preserving the environment. We supposedly have the largest recycling area (or something) in the U.S.
5. Arun Jiwa
This sounds like a really cool idea.

In rural India, there's been a lot of growth extracting the methane from cow dung to power biogas generators. I wonder if this type of "biosolid" solution can be used there as well?
Ben HM3
6. BenHM3
I used to live close enough to the world's largest sewage treatment plant* to smell it. No, it smells like the worst collection of laundry products you can imagine.

Anyway, the gasses produced are actually hard to use. Apparently they're corrosive as can be, and burn-off still remains the use-of-choice in some cases. (After the big bean festival?)

This gigantic plant--in Stickney**, IL--however no longer VISIBLY burns off the gasses, so they must've found some use for them. Perhaps their own district heating?

*They made this claim on a tour of the place in the early 90's, and expansion's never slowed. Oh, and touring a sewage treatment plant is really interesting. The pump house, from the Deep Tunnel, is the loudest place on earth. (Unfounded opinion of the author.)

**Just west of Chicago, on the river (ew) and yes, we always called it "Stinkney."

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