Algal biofuel production is neither environmentally nor commercially sustainable
http://theconversation.com/algal-biofuel-production-is-neither-environmentally-nor-commercially-sustainable-82095August 8, 2017
...Fossil fuel oil and gas originated from ancient algae in large measure, so the concept here is to replicate the essence of the creation of fossil fuels, albeit accelerated and optimised with modern chemical engineering. It was claimed that using algae would be much more efficient than creating biofuels from terrestrial plants and that the technology would make use of poor quality land not able to grow other crops.
Millions of dollars, euros and other currencies have been spent trying to get the algal marvel to work. Much of the money has been directed at refining the engineering process, electrically lighting the crop – which grows in a liquid suspension – harvesting and draining it. The solution to optimisation was seen as primarily technological non-biological, though species selection and growth conditions were also acknowledged as important factors.
However, it turns out that the hype has been misplaced. Our research has found that the production of algal biofuels is neither commercially nor environmentally sustainable. The attainable production levels are a fraction of those that were claimed. The amount of biofuel produced from prolonged culture of algae in pilot-scale systems is actually not too dissimilar from those of terrestrial plants: around 5,000 to 10,000 litres per hectare per year.
In fact, the rate of production from algae growing in the vast ponds required for truly massive production is, for a given area of land, similar to that seen in the most productive areas of the ocean. It amounts to around 4g of carbon from CO₂ fixed into biomass per square metre every day.
So what’s the problem? Why aren’t algal biofuels as good as had been hoped? Quite simply, it’s biology.
The dream has been broken not by failings in engineering, but by the inefficiency of biochemistry. Simulations of microalgal biofuel production show that to approach the 10% of EU transport fuels expected to be supplied by biofuels, ponds three times the area of Belgium would be needed. And for the algae in these ponds to produce biofuel, it would require fertiliser equivalent to 50% of the current total annual EU crop plant needs. Ironically, such ponds would also need to be located near heavy industry which produces CO₂ to provide the level required by the microalgae for photosynthesis.
The problem with third-generation biofuels has always been scaling up the production rates measured in small culture flasks to growth in thousands of cubic metres in size. In the larger cultures, the biomass density of the algae – needed to make the culture and harvesting processes economical – defeats desired growth rates because the organisms shade light from each other. This means that they do not get the sunlight needed to photosynthesise and produce the carbon-rich compounds needed for to make the biofuel fast enough....
