I found an interesting chart from a latest paper published by the Resources For the Future (RFF).
Finding 1: Biofuels are costly.
Finding 2: Unconventional oils are dirty.
Conclusion: None of them are an alternative to conventional oil.
Question: Am I saying we'd better stick to conventional oil?
Answer: No. Neither unconventional nor conventional liquid fuels are a desirable option for our sustainable energy future.
Suggestion: Hm.... Firstly, less travel. But people won't like it. Secondly, more public transportation. Come on, it's acceptable. See Asia or Europe! Thirdly, drastically more efficient homes and buildings. I hope governments can help poor people retrofit their houses.
P.S.: I know my suggestions are naive. But their direction is right. Let me study more and give you more persuasive solutions to free ourselves from liquid fuel addiction.
Source: Darmstadter, J. (2010). The Prospective Role of Unconventional Liquid Fuels. Washington, DC: Resources for the Future. [Full-text at http://j.mp/Unconventional_Liquids]