Though I'm pro hydrogen it has some substantial problems that may take time to solve.
1/ hard to store
2/ leaks are very explosive
3/ it may be clean burning but generating it needs to be non or low polluting too.
4/ volume generation just is not available at a practical cost.
5/ conversion from a gasoline/diesel distribution and usage system will be difficult and expense
Algae based biodiesel may be able to bypass all of those and give farmers a new cash crop.