Biodiesel from flax and cannabis (no need for chemical sprays) and recycled products (fish shop oil). I would make all the cars very expensive so people would prefer to use public transport.
No need to chop down forests etc for biodiesel - I would also buy out the cattle, sheep, cane and cotton industries and rehabilitate the land those disgraceful vandals have destroyed. Part of that land would then be put under biodiesel crops and the rest returned to native forests.
