[IamIan]

Originally Posted by P-hack

By magnitude, do you mean "multiple powers of 10"? If so what are you comparing?

"Orders of magnitude" ... is a bit different from just "magnitude".

For "orders of magnitude" ... it is common ... but not required for it use a base 10.... Link

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As for what am I in particular was referring / comparing to.

It was in reference to the broader view of energy use for vehicle movement.

Typical Photosynthesis for corn and such is usually around ~2% energy efficient ... the very best plants ... like Sugar Cane ... max out at around ~8% energy efficient.

Of that % of solar energy it converts ... a large % is consumed by the plant itself , to respire , to grow , to reproduce , etc.

By this point ... only a tiny % of the initial solar energy is stored in the plants products ... potato starch , corn kernel , etc... about ~0.25% to ~0.5%

Link

In order to use that stored plant energy to move the vehicle down the road it has to be converted / refined into a more usable form... that process itself is less than 100% efficient ... Like the plants ... the exact % of efficiency will vary from type to type ... and how much and what type of refining will vary with the situation of the engine that will be running it.

Perhaps the least energy intense form of refining would be things like ... chopping wood to burn as wood in a heat engine ... And the higher ends would include the use of microbes and other biological organisms that can result in as little as about ~23% net energy efficiency output.

Once you have the bio-Fuel ... you still have to convert it again ... in order to move your vehicle ... even if you managed as high as a 40% efficiency for the ICE you are running the bio fuel ... the net % of solar energy input to move vehicle energy output ... is tiny.

~0.25% to ~0.5% solar input to plant output ... even if we for the moment ignore other losses like refining , transportation and such ... just to run this ~0.5% through a ~40% efficient engine ... only gives about ~0.1% to ~0.2% of the solar energy input to the drive shaft.

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Compared to the non-Bio options:

For example ... PV can go over ~41% ( SpectroLab in 2009 achieved 41.6% ) ... of the solar energy input to electrical energy output ... with ~95% cycle efficient batteries ... and a combined motor and controller of ~95% efficiency ... that's getting around ~37% of the solar energy to the drive shaft.

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~0.1% to ~0.2% vs ~37% ... is between a 370:1 ratio to a 185:1 Ratio.

Even 0.1% to 0.2% vs 18% PV ... is between 180:1 and 90:1 ratios

Even if you want to use the common base 10 for the "Orders of Magnitude" ... the bio options are currently around 2 or 3 orders of magnitude bellow that of the non-bio options ... in terms of wider energy cycle efficiency from solar input to drive shaft output... and we haven't even yet included the other losses of refining , etc.

Even lower energy efficiency if it is a fossil fuel solar energy path.

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The exact ratios will vary of course ... among different specific bio option ... methods used ... and what specific non-bio it is being compared to ... etc.

But the bio is currently significantly less net cycle energy efficient from solar input to drive shaft output ... and there are no current scientific indications ... that I've read ... of that changing in the foreseeable future.