Growing algae of a specific, high-oil-content strain and keeping it free from contamination without spending a mint on closed bioreactors is tough.  Growing algae -- period -- is as far as I know pretty easy.

So here's what I don't understand.  Why worry about oil content at all?  Why not just grow large volumes of algae, skim it off, press out the water, and pryolise it to make synthesis gas (from which you can make gasoline, diesel, or any number of chemicals)?

Some of the original literature on algae and kelp pointed out that bacteria exist that can digest sea plants into methane - even in a salt water substrate.

Why not?  Harvest algae and plant overgrowth from waterways to turn into biogas and organic fertilizer.  Lakes, rivers, and even oceans need help dealing with fertilizer and manure run off.

Hypercar plugin hybrids could actually have biogas backup.  Very little compressed fuel would be needed.  

http://amazngdrx.blogharbor.com/blog

Responding to neg comment about closed bioreactors.

I doubt that closed systems should cost much more than open ponds.  Closed systems are merely pumping water/algae through stamped out double plastic sheets.  

Many advantages are claimed, such as controlling contaminants (including biological predators),  reducing water evaporation, increasing sunlight exposure.

Perhaps the increasing sunlight exposure is hype.  If algae 'block the sun' from other algae in a pond scenario, then who should care?  Algae that re blocking are receiving more sunlight, and by circulating the pond water, exposed algae are being recycled.  

So I would say the best system would not be Vertigro systems, where 'farms' are 6 foot high.  I would advocate:  one layer closed systems, flat on the ground, circulating the algae at increased density of algae.  There is only so much sunlight per square foot available.  And playing games with vertical growth systems won't increase that.