Blatant Reality

In a recent article on Genetic Engineer & Biotechnology News blog, the author states that the current process for growing algae is the reason that algae biofuels are not sustainable.

The question of energy balance is an essential factor influencing sustainability of biomass production. How much energy is in the biomass and how much energy is required for production and refining? One kilogram of dried algae biomass has a fuel value of 27 MJ. The state of technology indicates employing a paddle mixer to continuously mix an algae culture, the mixer requiring about 2 MJ of energy to produce one kilogram of algae biomass. The fertilizers required are also obtained by expending energy; for of algae, the energy required for this ranges from 5 to 12 MJ. Pumps will be required for harvesting, replenishing and emptying basins and maintaining water levels. Assuming a water volume to be moved of about 10 to 60 cubic metres per kilogram of algae produced, and an energy requirement of 0.1 kW per cubic metre, up to 16 MJ of energy are required per kilogram of algae. Finally, consider the energy required for harvesting: even assuming that the algae could be sedimented spontaneously or by adding flocculants and thus be enriched by a factor of 10, it remains necessary to further concentrate the remaining volume before drying. Considering that a separator requires 1 kWh per cubic metre, there is a further increase of 3.6 MJ per kilogram of algae. A band filter press would require half as much energy. A further 7 to 8 MJ per kilogram are required for drying the algae.

With recourse to the usual current technology, at least 35 to 45 MJ of energy must be expended in order to produce a “value” of 27 MJ in dry algal biomass. This simple estimate does not take into account many steps in the total production process of actual biofuel such as biodiesel that also require energy. The energy costs for transport, supplying CO_2 to the cultures, preparation and regeneration of culture media, cleaning procedures and finally, the extraction process, would have to be taken into account. It should also be taken into consideration that each step in the process is accompanied by a certain loss factor. The above estimate operates with the unrealistic assumption of zero loss during the procedures. The basic data used for this calculation are derived from practical experience at considerably smaller facilities. Higher energy costs are to be expected in larger facilities in the future, possessing multiple square kilometres, since liquids such as culture medium etc. will have to be transported over longer distances.

The author or this article is completely right; scientists have no problem getting oil from algae, they are just having problems to do it sustainably. However, this article doesn’t take into account several things.

1. This analysis only looks at algae produced through the use of sunlight, which isn’t the only way to grow algae. Other processes use artificial light in bioreactors (which would probably increase the energy use) or no light at all in fermentors (which some have said is the likeliest way we will mass produce algae for biofuels in the near future). Each of these growth methods use different processes that have different energy requirements.
2. The author also doesn’t take into account that a new method for harvesting algae and extracting the oil has been developed that uses 90% less energy than the methods stated above. This “Single Step Extraction” method developed by OriginOil uses an electric current and gravity to separate the oil from the water and biomass.
3. Lastly, the article assumes that energy is the only thing that matters with the growth and extraction of oil from algae. No where in the article is there any mention to co-products like pharmaceuticals, chemicals, or animal feed that can also be produced from the algal biomass. If these items can be produced as well, then a negative energy balance isn’t what to look at but instead the overall costs versus how much can be made from sale the cumulative products produced from a kilogram of algae.

Overall, this article does bring up a good point that, according to their numbers, the method of using sunlight to grow algae has yet to produce more energy than the process consumes. However, with so many different companies using various different methods looking into producing algae biofuels, I feel that this problem can ultimately be overcome in the long run.