Personal mobility and goods transports are two of the oldest human needs and among the largest energy consumers and polluters. The changes from leaded gasoline to its "unleaded" fossil substitute, which still pollutes the air with heavy metals, VOCs, NOx, CO and CO2, or to Diesel oil - which is an even worse polluter - or to polluting bio-fuels, do not solve the problems of excessive urban pollution and noise at all, and, in the case of fossil fuels, of the irresponsibly rapid resource depletion.
LPG or "natural", i.e. mineral gases, reduce the emissions to some extent, but still pollute, cause global warming and are depleting resources. They have no longer term future either !
Based on the actual technological state-of-the-art, there are only two really clean, sustainable options left: Hydrogen, if not used in low-efficiency combustion engines, producing NOx and steam, i.e. if it is preferably used for the on-board production of electricity for electric drives or direct electric drives, fed from batteries or electric conductors along the traffic routes, if both energy carriers are produced from clean, renewable energy sources.
Combustion engines with their extremely low energy efficiencies of only 15 - 30 %, their noise, pollution and wear-and-tear, even if clean fuels like hydrogen are used, and their expensive maintenance for lubrication oil, spark plugs, filters, catalytic converters and exhaust pipes, belong to the technical museum on the long run also for ship propulsion !
The future will be marked by the competition of clean energy storage, hydrogen - compressed, pressurized or embedded in metals - versus the emerging high density, long-life battery technologies. It will be an uneven battle where energy supply logistics into every corner of the world and storage cost will be decisive factors.
A more difficult problem to solve is the air traffic, where the electric option still seems to be too heavy and hydrogen might be the ultimate winner, provided it is available on all airports. However, the relatively inefficient, noisy airplanes might have to compete in future with a new generation of airships using inert gases for buoyancy and hydrogen as a propelling fuel.
Fossil fuel-intensive mobility sports like hot air ballooning, motor boat and car racing might have to be prohibited by law for the sake of conserving the last reserves of fossil fuel resources for the indispensable organic chemistry. But these sports might enjoy a renaissance with the clean options mentioned above.
However, the oldest, cleanest, most sustainable and healthiest means of mobility is the use of human or animal muscles, fed by the natural food chain as energy source - see the ISEO Chapter and promotional campaign for the use Muscle Energy.
The upcoming more complete energy statistics and world energy forecasting data, compiled by ISEO, will show the really sustainable energy potential and mobility trends.
from the "Blueprint for the Clean, Sustainable Energy Age" - order
The ISEO working groups will add more information.