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Re: [Phys-l] Biofuel Generator



The puff I quoted talks about direct CO2 to petrocarbons
via microbial activity, not photosynthesis.

Brian W

On 1/27/2011 10:52 AM, Kyle Forinash wrote:
This is interesting news but I'd be very skeptical of biofuel as a total
solution for US transportation needs.

Overall plant efficiencies are typically under 1% for converting
sunlight to biomass (and this is after millions of years of evolution at
work looking for more efficient ways to use the sun). The following
paper (below) claims that maximum possible plant efficiencies are
probably less than 8%. Using current soybean/biodiesel efficiencies per
square meter and planting the total arable land in the US for soybeans
(no food, no national parks, no lawns, all soybean) we could possibly
produce about 24-25 EJ of energy per year using current technology. Our
current annual transportation fuel consumption (primary energy) is
around 27 EJ. Sugarcane (which doesn't grow here) would produce a more
than we currently use but not by a whole lot. So biofuels might be a
partial solution for transportation (particularly if we engineer plants
to make fuel directly) but isn't going to be a one stop solution.
Commercial PV solar cells are around 20% efficient however .... (around
40 times more energy per square meter than surgar cane and a 6-8 month
energy payback time).

Electric cars might also be a solution but a quick back of the envelope
calculation (see my book 'Fundamentals of Environmental Physics'
Forinash) reveals that, for 50% efficient car and distribution
technology we would need about 450 more power plants (1000MW each of
whatever type; coal, gas, nuclear) which is half again as many as we
currently have (equivalent to around 950 1000MW plants). Doable but not
trivial. For 2MW windmills we need around 450,000 new windmills to
convert all cars to electric.

'What is the maximum efficiency with which photosynthesis can convert
solar energy into biomass?' X. Zhu, S. Long, D. Ort; US Department of
Agriculture, Agricultural Research Services.

I can send copies of this paper if anyone is interested.

kyle
------------------------------

Message: 9
Date: Wed, 26 Jan 2011 18:14:31 -0500
From: chuck britton<cvbritton@mac.com>
Subject: Re: [Phys-l] Biofuel Generator
To: betwys1@sbcglobal.net, Forum for Physics Educators
<phys-l@carnot.physics.buffalo.edu>
Message-ID:<a0624080ec9665ac75df5@[192.168.1.108]>
Content-Type: text/plain; CHARSET=US-ASCII; format=flowed

Dang!! All those moonshiners back home will be out of work if they
don't upgrade to this newfangled technology!!!!

;-)


At 5:05 PM -0600 1/26/11, brian whatcott wrote:
Fingers crossed!

Monday, January 24, 2011

Biotechnology firm Joule Unlimited may have come up with a game changer
in the quest for economically viable biofuels.

"---Our technology has already been proven with the direct
conversion of CO2 to --- ethanol, ----."

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