Algae as a Biofuel?

I was reading a blog the other day about a Chinese company looking to use algae as a way of absorbing carbon from their coal power stations. The idea is that given that algae needs only sunlight, carbon dioxide and salt water to grow it can be grown in mass quantities using the CO₂ from the coal station. This would in theory produce 'cleaner' coal and a useful by-product as algae can be used as both a fertiliser and as be converted into biofuel.

My problem with this is that are you really saving any carbon from entering the atmosphere?

After digging around for a bit, I came across some useful information in wikipedia. When biomass is burnt as fuel, it releases less carbon than was used in its growth for two reasons,

1. Approximately one third of the carbon absorbed by the plant during its life is sequestered in its roots, which are left in the soil to rot and fertilize nearby plant life, and
2. Combustion of biomass produces 1-10% solid ash (depending on type of plant used), which is extremely high in carbon (this ash is commonly used as fertilizer)

So given that we can convert the biomass into a usable fuel without consuming too much energy (or using energy from other renewable sources) then the net outcome is more power output for only slightly more carbon output. So really this comes down to a question of efficiency... are we better off spending the money researching and developing an algae based carbon absorption plant which then converts the algae into a usable fuel, or are we simply better off using that same money to improve the efficiency of our existing coal power station, or even investing in other renewable technologies?

The graph below gives some idea of the relative carbon intensity (carbon output per unit of energy output) of biofuels against fossil fuels. While it doesn't include algae fuels it does show that it requires less carbon dioxide to extract energy from biofuels in general. This, coupled with the fact that our primary source of food for growing the algae comes from a process that is also generating power, makes for a more efficient process than simply doing either independently and makes a better case than existing biofuels.

It really is hard to say without seeing the numbers. But given that the by-product of the algae may also be used as a fertiliser, and more importantly, that there is a significant amount of R&D in an entirely new field, then I am tempted to say that it is worthwhile. Because even though it may cost more to develop the algae technology, there are other advantages to broadening our approach to energy. For example, algae may be used as a natural source of hydrogen and it is possible to extract ethanol without having to harvest the algae.

In researching all of this I was pretty amazed to realise that biofuels really are becoming an established industry in themselves. I guess this is because they offer a solution that doesn't require major infrastructure changes and they offer a significant solution to the transport industry, which is one of the major (and in some ways hardest to fix) contributors to global CO₂ levels. The things is though, that although we are talking about a more efficient process, the use of biofuels (whether algae or otherwise) still never gets past the key point that we are still putting carbon into the atmosphere at an unsustainable rate. While biofuels may all make us feel a bit better about 'doing our bit', they will never be enough to reduce our carbon output to sustainable levels.