Everybody loves to hate 1st generation biofuels these days. Inefficient, polluting, do not scale well and net energy losers. In short: totally useless waste of money and energy in terms of energy production. Very useful for political gains though.
Now, some people are more optimistic about 2nd generation biofuels, esp. cellulosic ethanol and similar processes from plant based feed. However, serious doubts have been cast on their sustainability as well (economic, ecological and net energy wise).
The greatest hope has been given to algal biodiesel. It has been touted as the fastest growing (scaling), least energy input and best fuel output biofuel type. It was supposed to become an explosive growth area and solve our biofuel scaling problems.
Up until now.
Two posts, referencing some of the most realistic studies in the field, cast a really big shadow over algal biodiesel.
A direct quotes from Dr. Krassen Dimitrov's paper:
"Fundamental thermodynamic constrains make it impossible for such approach to be commercially viable for fuel prices below $800/bbl, even if flawless technological implementation is assumed." (emphasis added)This is not to say that biofuels from algae are not currently among our best bad hopes for biofuels replacing fossil fuels. It's still the best scaling and apparently best net energy ratio biofuel out there. Both currently and in theoretical improvements. (If somebody is thinking CTL, yes it's a probability for non-biofuel alternatives, but the ghg emissions are not pretty compared even to gasoline).
"A PBR-based biodiesel plant will have a maximum carbon mitigation potential of less than 30 kgCO2/m2/yr" (read: miniscule, emphasis)
"Biofuel production in PBR-based plants compares unfavourably with other alternative technologies for liquid fuel production, carbon mitigation and solar energy." (emphasis added)
Algal bio-diesel is just not enough.
Nothing known scales to 85 million barrels of use per day. Not even 1/10 of that. It is just not physically possible to grow that amount of biofuel. The land area, energy inputs and logistics do not make sense. Thus, the economic does not make sense either.
Still, algal biofuels will be made, will be improved and I'm betting there'll be an investment bubble around them, just as there's one now around bio-ethanol (1st gen), which is more or less complete bogus.
If you are an investor, you have been warned: don't try to break physics with an investment plan.