I was watching the news (ABC24) during my lunch break earlier today and it said that green fuels for aviation are achievable in 20 years.
This got me interested in bio-fuel again. There are plenty of guides available online and the price has been quoted as 70c per gallon. This is extraordinary and a target of manufacturers...they want to produce fuel locally rather than deal with buying oil from overseas.
Camelina Sativa is an important oil producing plant that:
"...needs little water or nitrogen to flourish, it can be grown on marginal agricultural lands and does not compete with food crops. It may be used as a rotation crop for wheat, to increase the health of the soil"
Suggesting to me that this plant survives in poor conditions and is rewarding with the vegetable oil it produces (more about this at the wikipedia page), a key ingredient in manufacturing bio-diesel.
It may not be clean, but it's cheap...and the money saved can finance something clean and renewable.