EVERYONE agrees algae seem a really great alternative, yet no one globally has ever made an economic way to turn algae into fuel.
Why?
Because of low energy density and high water content.
By the time you dry them out you've used 90% of the energy profit you could get out of it, and the last 10% isn't enough to pay for the investment into the fuel.
They don't even ferment well
So my solution:
Potatos!
they happen to grow in soils that aren't suited to cropping with intensive crops, could be used as a food source for local communities and are filled with starches... also added bonus VODKA!
But setting aside the booze for a moment, they have more energy per gram than algae and thus represent a better energy source.
Although I just had a crazy thought: use solar storage of heat and focusing panels to run the driers of the algae, then burn it for an increased energy profit...
That could work well, but would need ample supplies of seawater AND sunshine.
So the only place it would work well is the Mediterranean and they have oil by the butt-load.
Such is the way the world works I suppose.
FINALLY: regarding rainforests:
Slash and burn agriculture is NECESSARY to survive there due to incredibly low soil fertility, one of the reasons there are so many plants there is because the plants hold all the nutrients that flow through the rivers in the rainforest, gathering and storing them, and then more plants grow on their leaf litter and so-on.
When you want to plant useful crops, the crop takes up the nutrients in the soil, obviously, while rainforest has almost none IN the soil.
Their basic solution has for millenia to burn the forest to put the nutrients back into the soil, grow their crops for a few years and then move on to the next patch.
This is normal and the only problem with modern people doing it, is we do it at a rate of miles each year rather than making a clearing in the forest a dozen meters wide.
With the latter, the forest would regenerate, accumulating nutrients and growing as it does everywhere else.
With the former, the forest would take decades to recover to the point it could be reburnt even if they PLANTED the forest back in place.
I'm not saying it's a good thing they're doing their agriculture this way, far from it, however it's easy for those who grew up on fertile soils that hold the nutrients we put back to forget just what kind of soil they live with.
Honestly? Modern intensive agriculture which was developed for high fertility environments has no place near or in rainforest or similar low fertility environments, and unless people living around there learn and understand that we won't be able to make any progress, and if policy makers keep ignoring the issue then we can anticipate massive starvation in South America, and total deforestation.
...
Why are people such idiots?