Matt Fisher asked:
Hi Dr. Smith,
I've always wondered if human waste can, or is being used, to produce electricity.† I know that rotting cow manure and garbage can produce energy, but I've never heard of human waste used for this purpose. Seems like a great source of energy, and the infrastructure to collect it is certainly in place.† Can you shed some light on this?
We put this to Dr. Piers Clark, Commercial Director at Thames Water...
Piers - In Thames Water, weíve made energy from poo for many, many decades now and we do it through a process called anaerobic digestion. Anaerobic digestion is a process that's very similar to what happens inside your stomach actually when you eat food. It also happens when we ferment berries to make beer. Itís basically the gradual breakdown of organic matter through a natural process and the molecules that make up the food that we eat and that ultimately come out as poo gradually get broken down into a form of a gas and the gas is called biogas. Itís a mixture of methane and carbon dioxide. And carbon dioxide is naturally in the air and methane is the gas that people most readily associate with being the gas that you burn on your cookers at home. We run this natural process and have done so for many years. We produce about 15 million pounds worth of energy every year which equates to about 15% of our total energy usage in Thames Water.
Co-firing would seem the best compromise technology.
And for the Scotts:
That's Scots laddie
http://www.thenakedscientists.com/forum/index.php?topic=32920.msg318867#msg318867 RD, Fri, 9th Sep 2011
I wonder if Shakespeare had this in mind when he wrote Richard the Turd, or does it have more to do with Newton's Turd Law of Motions?
The only problem I have with it is how unsanitary human feces can be. It takes a lot of energy to fire it enough just to turn it into soil. Which, to me is a much more practical use for any excrement. JargonJam, Thu, 22nd Sep 2011
One of the problems with digestion of human waste is that the volume of gas that could be generated from an individual household is very small.
Why not put all the human excrement into an airtight building and let the waste breakdown into methane and put a gas valve into the room to let the gas escape into a tube leading to a big container where the methane is then it and heats up steam to move turbines and generate electricity there are enough humans on this earth to power the world and it would cost less because you will not be digging for fuels it could be directed from the sewage plants. The science enthusiast, Wed, 5th Oct 2011
"there are enough humans on this earth to power the world "
You might want to attribute that quote correctly; it's plainly from The Science Enthusiast. Bored chemist, Thu, 6th Oct 2011
i saw a 50' long 2 bag setup for collecting methane. They excrementized into a bucket & dumped it into the system= 3rd world rocket science !