Re: manure->methane -> power


<puppet_sock@xxxxxxxxxxx> wrote in message
news:1126715645.592266.11940@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Elmo wrote:
> [snip]
>> Gas cogeneration
>> systems can run 70-80% energy efficiency converting to electricity
>> leaving
>> (do the subtraction) as the waste heat.
>
> For suitable values of the word "efficiency." A heat engine
> cannot violate the laws of physics. To get 70 % efficiency
> out of a heat engine operating with a "cold" side round
> about room temperature, you'd need the "hot" side to be
> at about 900 C. That's high even for a dedicated power plant.
>
> It's likely that your reports are including in the efficiency
> calculations some estimate of the part of the heat used for
> whatever the "co" part is. Like, 30 percent goes to electricity,
> 40 percent goes to heating the building, total 70 percent used,
> so 70 percent efficient. Getting 30 percent out as electricity
> would only require a "hot side" of about 200 C.
> Socks
>

I'll delurk for this, as it's always been a fascinating subject, in my
opinion. I wrote a report on methane digestion systems in college. Look up
Ram Bux Singh and L. John Fry on the internet for two guys who got their
*** together on this. (Bad pun, I know). Mr. Singh was in India and used
a batch digester system, which was very labor intensive. Mr. Fry was in
South Africa, I believe it was, and perfected the continuous feed digester.
This is the one that makes the most sense. Fry had a 1000 head pig farm
wherein he dumped all the manure into a holding pond. Stunk to high heaven
and people in the adjacent town got on his case, big time. To the point of
threatening to shut him down. He buried some large cylindrical underground
tanks, welded end to end lengthwise, and plumbed one end to a concrete
manure settling basin outside his pig barn. He'd wash the manure out of the
barn every evening, let the straw float to the top, then run a mudpump and
push it into the underground tank. (Methane digester). It took about 30
days for his first batch to produce workable methane and bleed out all the
air from the top of the tank. The manure was pushed from one end of the
tank to the other. The effluent, (that's what he called it), that came out
of the digested end of the tank had only a slight smell of moldy newspapers
according to Mr. Fry. Took right at 30 days to completely digest and travel
from one end of the tank to the other. He found that the effluent was
almost a perfect fertilizer, in his opinion, and pumped it into a sprayer
tanker and would spray it on a local golf course. Got paid for that, too.
He fed the methane to a two cylinder, water cooled Lister diesel engine to
generate all his power. He pulled the fuel injectors out of the diesel and
installed spark plugs. Methane gas has a very high octane rating and ran
fine with no detonation at the diesels compression ratio. Had methane left,
so he plumbed it to his cookstove and some other things that I can't
remember now. Later on, he increased the rate of methane production in the
digester by running the coolant from the water jacket on the Lister to a
grid of pipes inside his digester to raise the temperature of the manure.
It's as close as something for nothing as I've ever heard of and Mr. Fry was
one sharp hombre, in my estimation. I can't for the life of me understand
why some of these big hog operations don't utilize this process.

(relurking)

Garrett Fulton


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