by Maria Georgakopoulou, MSc alumni in Bioeconomy / International Hellenic University
The global climate change has caused dramatic effects in the availability of resources, mainly affecting the food and energy sectors. The parallel rise of global population, estimated to reach nine billion in 2050, has forced the investigation of alternative sources, in order to find novel and sustainable solutions in the major problems we will be called to answer in the near future. The European Union has already started to look forward through the proposition of a bio-based economy, which requires agricultural crops to be used not only for food and feed but also for chemicals, materials and even biofuels.
Marine biotechnology seems to have something to propose in order to face all these challenges: microalgae. Microalgae are considered one of the most favorable and potent feedstocks for a sustainable supply of products aimed to the food and energy market and the scarcity of the available fossil resources increases the demand for alternative, bio-based products, with multiple uses.
But what exactly are microalgae?
Microalgae are microscopic aquatic photosynthetic microorganisms, they are autotrophs and they have the ability to transform sunlight, carbon dioxide and nutrients into biomass. Microalgae exist in every ecosystem on earth, aquatic and terrestrial, with a variety of more than 50.000 species, but with approximately 30.000 species being the object of studying and scientific analysis. The metabolic flexibility of microalgae, with their unicellular formation, permits them to adapt in a variety of environments, even with the presence of unsuitable conditions, due to their physiology, which relies on the accumulation of high added-value compounds. It is the unique adaptability of microalgae and cyanobacteria, which allows them to provide energy for growth and preservation, what characterizes them and makes them suitable as a sustainable renewable source.
Their advantages:
- short life cycles
- fast growth rates
- high productivity
- limited seasonal variation
- cheap cultivation with abundant raw materials
- no need arable land or fresh water and thus, have a clear advantage compared to the conventional plants.
Microalgae biomass, depending on the species and the extracted compounds, have a wide application in various fields, such as human and animal nutrition, pharmaceuticals, cosmetic products and the production of renewable energy sources.
Can we eat microalgae?
Microalgae are known to be cultivated for food purposes. In fact, the Food and Agriculture Organization of the United Nations (FAO), has highlighted the tendency towards the increase of demand for algal products on a global scale, as food supplements or as food additives. Other industrial, legal/governmental and even nutritional concerns have led algal research to develop novel food products and dietary supplements. Due to their biochemical composition, microalgae can affect positively the human well-being. They are known to have high levels of protein with vital amino acids and lipids with fatty acids, found also in the conventional food, but, in bigger quantities and better quality. Their rich vitamin content includes vitamins A, B1, B2, B6, B12, C, E, K, as well as nicotinic acid, biotin, folic acid and pantothenic acid.
The good news is that we already consume microalgae. Microalgae- based products are commercially available in the form of capsules, tablets or as additives to commodities such as beverages, pasta, candy and gums, for nutritional purposes or as coloring agents. Commercial species of the genus Chlorella are already available in the market, as dietary supplements, without any processing, other than drying.
What about energy?
The microalgal technology regarding the production of biofuels, depends on the cultivation and harvest of the biomass. However, the lipid content of each microalgae species is an indicator but does not determine the total amount of the biofuel yield.
The potential of microalgae as a considerable candidate for the production of biofuels, has to do with their capability to produce polysaccharides and triacylglycerides. These two compounds are among others, the ingredients of bioethanol and biodiesel fuels. The microalgal biomass, in order to produce various forms of biofuels, can be technologically converted into thermochemical and biochemical conversion, chemical reaction and direct combustion. The thermochemical conversion is one of the most common and feasible strategies regarding biomass conversion but the most immediate way to produce biofuel from microalgae is through Anaerobic Digestion, extracting biogas.
Within the bioenergy market sector, the microalgae- based products can be allocated, with the prediction that offer and demand for these commodities will increase substantially in the near future. The energy sector is characterized by relatively low market prices, due to the fossil fuels and unfortunately, the total financial turnover from the exploitation of microalgae biomass in the bioenergy market is significantly low.
Other uses
Wastewater remediation
It has been supported[1] that the production of biofuels, when combined with wastewater treatment, is expected to be the most effective commercial application of microalgae in the short term. For this reason, there are procedures by which organic and chemical contaminants can be removed, along with heavy metals and pathogens, during a wastewater remediation process at the same time with the production of biomass aimed for biofuels. The main incentives for this process are the reserves on the chemical compounds, because those substances act as microalgal nutrients, as well as the environmental benefits which arise from the reduced amounts of freshwater, supplying the biomass cultivation.
Cosmetics
The production of microalgae -consisting cosmetic products, enriched with antioxidants and various other bioactive substances, is considered a growing and with high potential sector. The need to create safe products, developed with environmentally friendly bioprocesses, has classified microalgae as a sustainable source of bioproducts.
Where are microalgae cultivated?
In almost every part of the world. India, China, Japan, Australia, Taiwan, Israel, the EU, and the US are among the regions that are leaders in the sector of microalgae cultivation and research, as well as this is where the industrial and commercial efforts are focused.
The main drawbacks
Toxicity
Besides the tremendous potential of microalgae on the sectors of food and health, microalgae produce certain secondary metabolites, the phycotoxins, with serious adverse effects. The last 40 years, there have been observed increased incidents of toxicity, with amnesic, diarrheic, and azaspiracid (AZA) poisoning through the consumption of fish. The cause of the episodes is the anthropogenic factor, as the pollution and the climate change are immensely connected with the microalgal toxic effect. Especially the presence of industrial waste facilitates the development of toxic microalgae, which spread and reproduce rapidly.
The risks of toxicity in microalgae and cyanobacteria, have led to thorough examination with the accumulation of toxicological data. When certain limits are reached in fish meat or in other commercial products, there is direct impact on the sector, with economic loss and skepticism from the consumers, retailers and wholesalers.
Economic sustainability
The variety of industrial and commercial uses of microalgae in the fields of nutrition, health, biofuels, cosmetics, and environmental protection, emphasize their high potential as a renewable source and have increased the global interest in the relevant fields of research.
However, the low capacity in production leads the global market to consider it as an unrealistic solution, as the biomass is not yet adequate for large scale production, especially in comparison to other conventional sources of food and energy. Economies of scale are always an important factor in the production and market exploitation of the microalgae-based products and unfortunately, they still have not been achieved. The high amounts required as fixed capital combined with the labor costs leave small room for competitive prices and efficient average cost of per kg dry weight mass.
The improvement opportunities
Microalgal biotechnology has emerged because of the diversity of the products that the algal biomass can develop. The ambiguous future that unfolds ahead with the food and energy deficiency, in comparison with the climate change, leads to the microalgal biomass examined as a serious alternative to the emerging problems encountered.
In order to enforce the economic feasibility, more efficient production systems need to be designed, with the contribution of the technological advancements. Considerable reduction of the production cost can be achieved with the parallel retrieval of nutrients from residuals, while producing biomass. The advancements should be supported by biotechnological breakthroughs and development of more efficient and with improved biochemical composition microalgae strains.
Technological advancements and environmental challenges can also leave room of improvement and the creation of large-scale production systems. The diversity that the various species of microalgae show is prone to invent new applications and commercial products. With more accurate estimations and experience gained over the years, with innovation combined with economic feasibility and, more importantly, with active engagement of important public and private stakeholders, the necessary investment and practical implementation of the microalgal applications would overcome the current challenges and the microalgal industry would develop viably.
The challenges are many to overcome in order to reach viable, economically feasible and sustainable solutions regarding the full- scale exploitation of microalgae. But the huge potential of these microorganisms has driven many scientists all over the world to search for inventive answers to the problems and ways to unfold the microalgal capabilities.
Acknowledgments
We are grateful to Ms Georgakopoulou for kindly providing the original article.
[1] Van Harmelen, T. and Oonk H. (2006). Microalgae biofixation processes: applications and potential contributions to greenhouse gas mitigation options. International Network on Biofixation of CO2 and Greenhouse Gas Abatement with Microalgae, Apeldoom, The Netherlands
References
Draaisma RB, Wijffels RH, Slegers PM, Brentner LB, Roy, A, Barbosa MJ. (2013). Food commodities from microalgae. Current Opinion in Biotechnology. 24(2): pp. 169-77.
Enzing, C, Ploeg, M, Barbosa, M, Sijtsma, L (2014) Microalgae-based products for the food and feed sector: an outlook for Europe. European Commission, Joint Research Centre, Institute for Prospective Technological Studies.
Forján, E., Navarro, F, Cuaresma, M, Vaquero, I, Ruíz-Domínguez, MC., Gojkovic, Ž., Vázquez, M, Márquez, M, Mogedas, B, Bermejo, E, Girlich, S, Domínguez, M J. Vílchez, C, Vega J M. and Garbayo I. (2015). Microalgae: Fast-Growth Sustainable Green Factories, Critical Reviews in Environmental Science and Technology, 45:16, 1705-1755.
Frac, M., Jezierska-Tys , S., and Tys, J. (2010). Microalgae for biofuels production and environmental applications: A review. African Journal of Biotechnology Vol. 9 (54), pp. 9227-9236.
Van Harmelen, T. and Oonk H. (2006). Microalgae biofixation processes: applications and potential contributions to greenhouse gas mitigation options. International Network on Biofixation of CO2 and Greenhouse Gas Abatement with Microalgae, Apeldoom, The Netherlands.
Voort, M.P.J. van der Vuylsteke, E.. Visser, C.L.M (2015), Macro-economic of algae products. Public output report of EnAlgae project number WP2A7.02, Swansea http://www.enalgae.eu/public-deliverables.htm.
Wells, M L., Potin, P., Craigie,JS., Raven, J A., Merchant, S S., Helliwell, KE., Smith, A G., Camire, M E and Brawley S H. (2017) Algae as nutritional and functional food sources: revisiting our understanding. J Appl Phycol. 29(2): pp. 949–982.
Wijffels, R.H. , Barbosa, M.J. (2010). An outlook on microalgal biofuels. Science, 329 (5993), pp. 796-799
