pstarr wrote:Yes. Biofuels have additional inputs: free solar and free photosynthesis. The plants take solar, CO2, to synthesize carbohydrates, starch, and sugars, the inputs into fermentation/distillations processes.
Efficiency of photosynthesis (real world) is around 0,5-1%. Efficiency of liquid fuel extraction from biomass is around 30%, so you end up with an efficiency of around 0,2% from sunlight to biofuels. Use this in a combustion engine with an average efficiency (real world) of 20% you have a cobersion rate of less than 0,05% from sunlight to power at your cars wheels.
This would not be aproblem if we would only have few cars in the world or unlimited space. In reality we have neither.
Yes. But the CO1/H20/Energy system requires concrete, steel, fossil fuels, and electricity.
My point is not that one is better than the other, but really both are loosers, not solutions.
Efficiency of a PV solar power plant is 10%. Efficiency of electricity transportation to batter charging to electric drive is 50% or better. So for the solar-electri path you have an efficiency of 5%, a hundred times better than the biofuel conversion process.
If you use your 10% PV power plant and make methane with 50% efficiency and use that in a combustion engine with 20% efficiency you end up with 0,5% efficiency from solar energy to power ta your wheels. 10 times worse than the pure lectric path, but still 10 times better than the biofuel path.
Solar methane or batteries need raw materials, but that imput is not a problem. Solar PV EROEI is now 10:1 to 20:1 and the other systems are irrelevant to the material use of the cars itself (no matter how they are powered)
So a combined solar-electric + solar-methane-combustion engine system will be doable and will provide 10-100 times more power per m² of area.
In a country like Germany without unlimited farmland and lots of energy /fuel needs this is very important.
because either solution has untended consequences such as AGW, ozone depletion, erosion, water depletion, etc. etc.
The solar-electric and solar-methane path is much, much, much better than the biofuel path in that regard. Solar PV in the deserts is no problem. Try that with biofuels... Erosion?Zero problem (solar PV plants even prevent erosion)