[Bioconversion] combined cycles

[Paul Harris]

G'day All,

I have noted the comments on "political" posts, but part of the world's
problem is that "problems" are often solved in isolation, with little
knowledge/consideration of possible side effects. I hope I'm being
realistic rather than political.

Please excuse my sarcasm, but even at the "wonderful" 50% efficiency
half the enegy going into the boiler is going up the chimney!

I think it is time we changed or an energy economy and properly
accounted for all the energy involved, as Joules are the same
everywhere, cannot be devalued and cannot be made or destroyed.
"Economics" only favours using fossil fuel to produce ethanol because
the cost of extracting oil and coal (which in turn is subsidised by
cheap fossil fuel prices) is valued so cheaply, as is human labour in
many countries. I think it would be more efficient system wise to just
use the fuel used to produce ethanol directly for transport (but that's
not quite so much fun as farming/distilling).

If we keep "extracting" carbon from the soil (in this case organic
carbon by growing plants) the agricultural system will fail, and this
carbon also ends up in the atmosphere! Nature is very good at
sustainability until homo sapiens get involved and try to chnge the
energy balance!

HOOROO

AJH wrote:
> 
> On Tue, 19 Jun 2007 12:50:07 +0930, Paul Harris wrote:
> 
> >Any conversion of energy is inefficient, so wastes our precious
> >bioenergy - <snip>
> 
> I agree but need this always be so?
> 
> I think the first coal fired engines were about 1/4% conversion
> efficiency but now direct fired coal gas turbines in combined cycle
> are said to achieve over 50% conversion.
> 
SNIP
> >
> >Gaseous fuels are best suited to stationary applications and any liquid
> >fuel will be needed for "emergency" uses.
> 
> Maybe but it's economics that will dictate.
> 
> A few days ago I asked a question about the amount of remaining carbon
> is digestate slurry after  an "economic" residence time in a biogas
> digester. The reason I asked is because UK government has moved the
> goalposts again and there seems to be more emphasis on digestion of
> specially grown rawstock. Like you everyone involved seems to think
> the "spent" slurry should be returned to land. I just wonder if there
> is scope for working a pyrolysis gasification process in series with
> it?
> 
> AJH
> 
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-- 
Mr. Paul Harris
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