The place of diatoms in the biofuels industry

221 ISSN 1759-7269 10.4155/BFS.11.157 © M Hildebrand A frequently stated reason for choosing unicellular microalgae as biofuel-production organisms is that they are more efficient than vascular plants at turning light and nutrients into valuable products. The economics of algal biofuels is critically dependent on productivity, and one can apply the same criterion and ask the question: among the microalgae, are certain classes more productive? Before answering that question, we need to acknowledge that within a given class of algae, there will be differences in measured productivity values when comparing individual species. These differences can stem from intrinsic factors related to their cell biology or from growth conditions at the time of sampling, which can involve both environmental and ecological variables. Comparing productivity in controlled culture conditions has value, because it reflects what is possible, but it also encompasses biases due to the fact that conditions are never exactly the same in two culture systems. Indications are that algal biofuels will be developed on a regional basis in a wide variety of environments [1]. Another consideration is the utility of comparing maximum productivity values. In a production system operating for a good portion of the year, it would be far more desirable to have strains that are consistently productive under a variety of environmental conditions than strains that have higher productivity under optimal conditions for a shorter period of time. A final consideration in productivity comparisons is that if the number of studies is relatively small, which is usually the case, poor statistical comparisons result. An alternative to measuring productivity values in culture is to evaluate an algal class’ productivity on the basis of its abundance in nature in a variety of environments. This approach may directly relate to biofuel production systems that would be deployed in different environments and provide robust statistics, since the sample size is large. Diatoms (Figure 1) are among the most productive and environmentally flexible eukaryotic microalgae on the planet. They are estimated to be responsible for 20% of global carbon fixation and have become the dominant primary producers in the ocean [2,3]. In addition The place of diatoms in the biofuels industry