"Pete C." wrote:
>
> The algae based biodiesel seems to have pretty good potential and can be
> produced in non-arable areas.

No, it doesn't. The field is dominated by
government-supported charlatans. There are
two big problems.

One is that large closed cultures cannot be kept pure.
Algal virii and algal grazers (such as rotifers)
will get in there and eat the algae. Open cultures,
of course, will be contaminated with whatever
the wind blows in, so they have an even worse
problem. The most successful algal culture systems
use organisms such as _Spirulina_ or _Haematococcus_
which can be grown under stressful conditions (such as
high salinity) that suppress other species.

The other is heat. A dense algal culture is
almost black. It is a very efficient absorber
of solar energy, and it gets hot. If it gets
too hot, the algae die. Open cultures have the
advantage that they can be cooled by the evaporation
of water, but then you face the problem of getting
enough water to run your culture system. And it
must be pure water, otherwise there will be a
salt build-up in the culture medium.

Mass algal culture for fuel is pipe dream.
The only people in the field who are not
delibrate charlatans are delusional scientists.