| Answer | Crossword Clue |
|---|---|
| PEAT | Fuel from a fen |
| PEAT | Fuel from a marsh |
| COAL | Fuel from a mine |
| PEAT | Fuel from a bog |
| PEET | Fuel from a bog: Var. |
| BIODIESEL | Fuel made from vegetable sources (and a 2006 dictionary addition) |
| ALGAE | A Berkeley scientist has figured a way to make hydrogen fuel from these |
