Based on the numbers quoted they are looking at about 1,000 gallons to the acre gross return. With efficient counter current heat exchangers, and depressurising energy recovery pumps (an analogue of turbo chargers in cars) and all the other automated systems that will eventually be part of a mature technology, the process ought to eventually reach efficiencies of a net return of around 600 gallons to the acre. That is useful. Enough to power everyone on the planet into the high middle class western lifestyle using about 25% of the land area (which would mostly come from roofs and deserts). If the process is really efficient, the only inputs are CO2 and water, everything else is recycled. The hydrocarbon fuels extracted contain only carbon, hydrogen and oxygen – and as little oxygen as possible.
So yes – it is a useful alternative approach, one I have been following for a decade or so.
Direct solar photovoltaic is still the most useful option, as it allows for the possibility of manufacture and deployment in space, which provides the basis for a set of mitigation strategies for several low probability high impact threats.
It is not perpetual motion – it is a simple case of biological production.
In its simplest form, photosynthesis can be characterised as using photons from the sun to separate hydrogen from oxygen of water, and release the oxygen, separate carbon from oxygen of carbon dioxide, and release the oxygen, then combine the hydrogen and carbon to given hydrocarbons that can be used as fuel.
Within biological systems those hydrocarbons are broken down through the Krebs cycles to power most biological function – we prefer to burn them in internal combustion engines at present.
The figures I gave were per year, and I was at pains to point out that they would come from mature technologies.
The algae do not require metal growing tanks, only metal processing tanks at the end of their growth. The ratio of metal to output hydrocarbons on a 20 year service life is very small.
The growth efficiencies of biological systems are well characterised.
Simple algae such as these can be extremely efficient converters of sunlight to biomass, you just have to control the predators and pathogens and other environmental growth parameters (as with all biological systems).
It is just a variation on a theme of industrial agriculture in a sense, and a lot of people have been working on it for a long time. Some species of algae produce up to 30% of their biomass as useful diesel fuels anyway.
It is a complex topic, and this announcement seems to be a useful step in improving efficiencies of conversion of non-diesel biomass to hydrocarbon feedstock for further catalytic conversion in oil refineries.