>>> I saw someone claim (on piclist a long time ago?) that if you 
>>> calculate
>>> the delivered efficiency of biomass (So much solar flux per km^2 
>>> yields
>>> so much energy in sugar, alcohol, or carbon), there is no way you 
>>> can
>>> even support the worlds current appetite for energy, much less 
>>> projected
>>> energy demand.

>> I too disbelieve it in its more extreme forms, but the claim was in 
>> fact that ALL terrestrial energy sources which may be considered to 
>> replace finite lifetime hydrocarbons, failed to deliver a net 
>> energy gain and that " we're

> What is a 'net energy gain' ?!

Assume you had NO energy resources whatsoever.
Your target is to ven "energy" to a customer.
Take every energy investment that you make as a debit and the amount 
of energy that you can deliver as a credit.
Energy would be expended in prospecting, mining, processing, 
delivering and handling.

The argument was that, after the higher grade hydrocarbon stores are 
exhausted, there is no available terrestrial energy source available 
that produces more energy than it consumes in its production. This 
would (presumably) include shale oil, biomass, wind, wave, ... . To be 
useful it would also have to include deep oceann methane and other 
deposits. I didn't find the arguments as ut convincing BUT it was said 
to be based on suitably detailed and authoritative research.

Regardless of whether the case is true r not for "conventional" energy 
sources, nuclear fusion utterly romps home, IF you can do it and IF 
you can fuel it. Lunar Helium (deposited from the sun via the solar 
wind), while still not proven, would be a sustainable source of 'fuel' 
(at least for the next billion years or two).

> Maybe we should wait until this is tested at least in a one-off 
> trial ?

Trial of obtaining the 'fuel' or of getting fusion going :-) ?
On present planning NASA intends to be back on the moon by 2018 (and 
about time too). If anyone cared enough tests could be done long 
before then. Many expect to have achieved controlled fusion by then.



        RM 

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