Comment Re:So why use trees? (Score 3, Insightful) 112
algae has many great aspect. It's achilles heels are 1) separation is very expensive 2) it's hard to get enough C02 into the water to do this at scale 3) it can get infected easily 3) inhomgenous growth requires active stiring or other tricks to bring a pond to harvest all at the same time 4) it's not that fast to grow-- poplars and switch grass are more efficient bio mass producers. Ethanol can be made from waste products too.
The upside of algae is that were starting to learn how to use some of it's byproducts and this offsets the costs. and incremental progress is being made on all these aspects. We haven't been growing algae as long as plants so there's potential headroom to grow. It can grow in seawater. lipids are better fuel than alchohol. And finally it's potentially less energetically expensive to sperarate lipids from water than alchohol from water. That step accounts for something like 1/3 of the cost of ethanol.