I’ve been on the fringes of the alternative fueled car area ever since college in the 70s. The market economics have never been workable. That may be changing.
Hydrogen does not and never will make economic sense, other than in the most exotic applications. Yhe space shuttle is the best current example, because MASS energy density is the critical measure. However, the space shuttle can pay the price of carrying LIQUID hydrogen, with a density far exceeding the extremely costly, bulky, and clumsy 5000- or 10,000-psi gaseous hydrogen tanks. But like the nuclear powered carrier or submarine, it just cannot be scaled down to less than gigantic size.
But that tank of liquid hydrogen actually holds less than 2/3 the hydrogen present in the same volume of gasoline - and barely over 1/4 the energy content! So hydrogen is a boondoggle, and so is ethanol, which has only 2/3 the energy content of gasoline. Butanol - from biological sources - is a far better alternative.
Transportation - gasoline, diesel, and jet fuel - account for over 2/3 of our petroleum consumption. And more than 95% of these products are made from petroleum. These light liquid hydrocarbons (LLH) that are the transportations fuels of today will serve the same role for many decades in the future. The only change will be the raw materials from which they are made.
“Found” petroleum is valuable because of its energy content. What you put in your tank contains about 85% of the energy content of what came out of the well. Non-petroleum sources will require added energy to assemble those large hydrocarbon molecules from more elemental sources of carbon - perhaps from CO2, waste products, coal, or other sources - and hydrogen, probably from brackish or partially treated waste water.
Right now I THINK that bioengineered bugs - bacteria or algae - will be the major new source, probably grown in transparent tank farms in sunny climates near industrial CO2 sources.