I have written on the subject of producing biodiesel from algae before, and it now looks that Royal Dutch Shell plc and HR Biopetroleum are to build a plant in Hawaii to grow algae and turn it into fuel. One very attractive feature of the strategy in general is the amount of diesel that might be "grown" per hectare compared with that derived from plants. According to the best estimates, somewhere over 100 tonnes of fuel might be synthesised per hectare from algae while 10 tonnes would be good going for the best crops, e.g. palm soya or jatropha, and probably just a tonne or so from rape.
Furthermore, since the algae need to absorb CO2 to grow their carbon weight, they offer a potential advantage of carbon sequestration, since although CO2 is released when the diesel is burned, the growth of the next crop of algae will take-up more of this important greenhouse gas. However, it is my understanding that the highest yields of algae involve using forced conditions of CO2 concentration which must be pumped into the reactors rather than simply leaving them open to the atmosphere to absorb ambient concentrations of the gas. It would be beneficial perhaps to locate algal production plants next to fossil-fuel powered electricity generating stations from which to catch CO2 and feed it to the algae.
However, the Hawaii facility intends to use open-air ponds to grow the algae in, which will be unmodified marine microalgae, indigenous to Hawaii, using patented methods. Presumably the latter have got around possible risks of contamination by other algal species with a lesser final yield of what is sometimes called "algoil." The technology has one more substantial benefit, and that is that unlike growing crops for fuel, which must eventually compete for a limited area of arable land with growing crops for food, the algal ponds can be placed on any land, including coastal areas which are no use for conventional agriculture.
The facility under question will be run by a Shell/HR Petroleum venture company, called Cellina, and will actually be located on the Kona coast of Hawaii Island, near to other facilities which also grow algae mostly for pharmaceuticals and food. The Cellina facility will use high pressure CO2 from cylinders to explore the potential of applying the gas from industrial e.g. power plants, as noted above. There is also a reduced demand on freshwater, which is likely to fail in supply worldwide and which some have predicted there will be wars over, since the algae can be grown in ponds filled with seawater.
I think this a very positive step, and it will be interesting to see how the project develops and if it is successful, just how easy it is to scale up the technology to match anywhere near the 30 billion barrels of oil from petroleum the world uses annually. In the latter respect, if technology based on algae is to provide part of our salvation in the Oil Dearth Era, it needs to be installed large and soon.