Justis, the problem with bio H as I see it is area for production. You need a huge surface area of shallow water, covered with a clear plastic/glass to prevent evaporation and to collect the hydrogen whilst at the same time allowing the photosynthesis. Maintenance of the water for such an area would be costly in terms of energy.
The maximum energy you can get from the sun is about 750W per sq. metre - that's with the sun directly overhead on a cloudless day. If the bio-H is 10% efficient that would be exceptional, so 75W/sq.m. That's not much energy.
Please don't lump me in with the plain old naysayers. I've run my car on waste cooking oil, and looked at growing special palm trees for fresh oil - but the areas involved to keep one car running are huge, plus the extraction time and cost.
I think electric will be the way eventually, with magnesium air batteries becoming available (rapid recharge, high capacity) and within a few years I'm sure they'll be superseded by something better.
