(Ph.D., M.Sc., MBA)
Science Director, SBAE Industries
Since the beginning of the Green Revolution the human population has increased by an additional 4 billion people. Those are 4 billion people with an ever increasing need for reliable food supplies and safe drinking water as well as the wish for reasonable living conditions. By 2030 an additional 1.5 to 2.0 billion people will be here with the same needs or even more so. The Green Revolution is nearing its limits to what it can do to support these additional people.
First of all, let it be clear that we are not using Earth’s resources efficiently. In fact, a huge part of the available resources are not used at all, or only marginally so. While about 70% of the world’s available freshwater is used for modern agriculture, more than half of which in an unsustainable fashion, more than 97% of the world’s water supply remains unused. The oceans were the cradle of all life on earth and form the basis of the world’s fisheries and aquaculture. There are enormous tracts of the oceans that are exceptionally fertile and productive and that are fairly easily accessible. We have all the production area that we could possibly need. We just never really thought of it that way.
We already have the skills to use these untapped resources. True, about two thirds of the 150 million tons of annual marine production today consists of simple capture of naturally growing creatures. But much like the first Green Revolution consisted of exporting existing agricultural techniques to the entire world, equally so we find that most of the required techniques to farm the oceans sustainably are readily available. Some techniques have been around for many centuries, while some were developed during the past decades. All of which are fully operational and ready to expand.
Micro-algae are a very diverse set of organisms and are typically divided into roughly twelve major groups. To give you an idea, there is more difference between the species of any two of these groups than there is between us and a kangaroo. One of these groups is the group called Diatoms (Bacillariophyta). These micro-algae are mostly unicellular but can occur in colonies. They live in freshwater, brackish water and marine systems all over the world. Their most striking feature is their unique cell wall which is made of hydrated silica. Diatoms live in glass houses.
Diatoms are very productive and are considered to account for about one third of the world’s primary production (measured as plant biomass) and to generate about 50% of the world’s oxygen. They are to a large extent the green lungs of the earth. They produce oil (lipids) as both structural and storage molecules. They are highly nutritious and form the starting point of the food chains in the oceans. They are rich in essential fatty acids (oils), energy molecules (triglycerides) and essential amino acids. They produce massively in the oceans and, what hasn’t been eaten by fish or other marine life, settles to the bottom of the oceans. Over the past millions of years a lot of these sinking diatoms have accumulated and a substantial part of the petroleum reserves consist of fossilized diatom biomass.
Why are they so successful? The answer in part lies in the use of hydrated silica for the cell walls. This is substantially different from most other algae who build their cell walls from organic carbons like cellulose and hemi-cellulose. Depositing silica in structural forms requires only about 6.5 % of the energy required to synthesize cell walls made from carbohydrates (Raven 1983). This leaves a substantial amount of excess energy that the diatoms can now use for useful metabolic purposes such as growth and reproduction. It has been suggested that the silica (or glass) through its beneficial optical properties conveys light more efficiently towards the interior of the diatom cell (Becker 1996).
In addition, Diatoms have evolved their own pigments, such as fucoxanthin. These pigments enable them to capture extra energy from sunlight in the range of 450 to 540 nm wave length and peaking at 510-525 nm. They can ‘harvest’ a larger portion of the light spectrum and do so at lower intensities. This is one of the biological mechanisms that enable them to be the very first of all micro-algae to flourish after the dark winter months and then continue to be productive during late autumn.
The combination of silica biology and efficient pigments results in a substantial energetic competitive advantage that diatoms have over their fellow micro-algae. The advantage of diatoms is as effective as it is simple: capture more sunlight energy and use this energy more efficiently to produce more cells. As a result some diatoms can divide up to three and sometimes four times per day. It is no wonder they have become one of the most diverse and abundant groups of algae.
Diatoms and their production potential have not gone unnoticed. Because of their exceptional productivity and oil properties, diatoms were proposed as one of the more interesting groups of micro-algae that needed further development, for instance towards biofuel applications (NREL US DOE 1996).