From a layman's point of view:
Gasification seems like the way to go with algae and any other organic material because you don't have to build a plant to expell or squish out the oil, you just have burn it out using very little oxygen (i.e., smoldering coals). Since you are not really burnuing up the "fuel", but rather gasifying it, you now have an opportunity to collect the fuel as a gas or convert it back to oil - think of the tarry pitch you get on the bottom of your camping cookware when you use it over an open fire. but how do you take the gas and convert it to oil? You run it through or over a catalyst! But as mentioned here: "Has anyone got any idea what catalyst would be used here. If this is true, then one of the biggest obstacles with algae will be solved, that being commercially viable extraction and processing"
Catalysts appear to be a closely guarded secret in any business as you will find the term used loosely, but never clearly defined. From my research, it appears that the catalyst for this application is some kind of metal. Several metals seem to be acceptable, from iron ferrous to Zinc, But most recently I have come across some indication that a mixture of cobalt and magnesium oxide will work.
From what I can tell (chemistry for dummies - remember, I am a layman), the catalyst attracts the hydrogen molecules and affixes them into place so that the other molecules (i.e., carbon and oxygen to name a few) in the gaseous mixture can more readily align and attach to the hydrogen molecules (otherwise its a kaotic affair and the chance for alignment is lessened greatly, hence the catalyst) which after becomming satured, fall off as precipitate, ready to be collected as oil. ??? I may not have it 100% correct, but I definitely have enough to experiment with and that will be the fun part!
Good Luck and remember to Take it to the Streets!