Nice idea, just a quick glimpse of that setup though tells me it's not real likely to go in the trunk any time soon... if that test cell was the size of a car battery, and one could find room in a vehicle for 60 of them... the output was barely turning a propellor on a small motor, let's be generous and say it got 100mA at 2V... 0.2W.... so 60 of them would give you 12W... and if they made it 10X more efficient... 120W... 100X 1200W... about there it's getting to be enough to shove around a wheelchair... so at about 100X efficiency you can probably fill a full sized van with the cells and get it to move...
So it would be back to the problem of bottling the H2 and providing safe point of use storage tanks... which is what is keeping H2 from deployment now. Since CNG tech is well developed it would probably be better to develop more efficient methane producer bacteria. Particularly as methane-tech fuel cell development is well underway.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice
Of course for a vehicle there is still the problem that the hydrogen must be compressed, since bacteria probably can't generate enough hydrogen to sustain about 40HP of output. I think instead the bacteria farm would be at home, then a solar- or wind-powered compressor could smush the fuel into a portable tank.