Phytoplankton: Biodiesel Production and Other Applications for Marine Biotechnology
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also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll and require sunlight in order to live and grow. Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight penetrates the water. Phytoplankton also require inorganic nutrients such as nitrates, phosphates, and sulfur which they convert into proteins, fats, and carbohydrates (NOAA 2017).
is defined as a renewable fuel that can be produced from a wide range of vegetable oils or animal fats. May be used either as a replacement for or as a component of diesel fuel. Technically it is a mixture of monoalkyl esters derived from lipid feedstocks, such as vegetable oils or animal fats (Negm et al. 2017).
- Marine Biotechnology
is the application of science and technology to living organisms from marine resources, as well as parts, products, and models thereof, to alter living or nonliving materials for the production of knowledge, goods, and services (OECD 2017).
Oceans dominate the planet’s surface (Abida et al. 2013) and provide important ecosystem goods and services, such as oxygen production, carbon retention, nutrient recycling, and pollutant filtration, which are critical to ecosystem functioning (Ritchie et al. 2013). The microscopic photosynthetic organisms that live there contribute ca. 50% of the oxygen we breathe includes much of the food and mineral resources extracted from the sea (Abida et al. 2013). The marine ecosystem is extremely dependent on interactions between plankton and the surrounding environment (Beaugrand et al. 2010; Beaugrand and Kirby 2010). These organisms can be found in all marine environments, including extreme conditions, and are extremely diverse, both in taxonomic groups, trophic groups, and sizes (Abida et al. 2013). It seems likely that human population growth, the future effects of climate change, and the possible shortage of unused arable land will encourage the exploitation of microalgae production systems (Darzins et al. 2010). In times of ecological crisis and major changes in society, it is essential to turn our attention to the sea in order to find additional solutions for a sustainable future (Abida et al. 2013). Interestingly, while many marine resources are overexploited, especially fisheries, the planktonic compartment of zooplankton, phytoplankton, bacteria, and viruses, which account for 95% of marine biomass, remains largely unknown and underexplored (Abida et al. 2013). In fact, microalgae support most of life on our planet and are highly productive on a global scale, with 1–4 cell duplications per day (Darzins et al. 2010). They also have the potential to produce up to 100 times more oil per hectare than any land plant and the advantage of not competing for space as they can be grown on noncultivable land using a variety of water sources (Udakis 2012).
Due to their diverse evolutionary origins, planktonic organisms offer many opportunities for new resources in medicine, cosmetics, food, renewable energy, and long-term solutions to mitigate climate change (Abida et al. 2013). Human exploitation, coupled with other factors, is affecting marine ecosystems at a rate that challenges our ability to provide innovative, effective, and adaptable scientific solutions. As a result, its sustainability is at stake (Pauly et al. 2002). A better understanding of the wide range of plankton and its interactions with the marine environment would allow for a prediction of its large-scale impact on the marine ecosystem and provide in-depth knowledge about pollution and climate change (Beaugrand et al. 2010; Beaugrand and Kirby 2010). The development of a sustainable management strategy will be largely dependent on the knowledge of how biological resources and the environments in which they live respond to natural variability and human induced change (Pauly et al. 2002). Exploitation of marine biological resources should therefore be conducted in such a way as to maximize the integrity and sustainability of ecosystems for future generations (Ritchie et al. 2013). Numerous technological developments, including micro and nanotechnologies, have been made in this regard (Beaugrand et al. 2010; Beaugrand and Kirby 2010). However, organisms and resources in areas outside national jurisdiction are considered by many to be shared resources, although some countries have full capacity for access, development, and benefit, exacerbating existing global inequalities and reducing the ability of developing countries to innovate and develop sustainably (Ritchie et al. 2013). The aim of this chapter is to analyze the usefulness of phytoplankton in the biodiesel industry, microalgae as an alternative fuel source, microalgal biomass production, and algae-based biofuels in the framework of the new technologies of sustainable exploitation.
Technologies of Sustainable Exploitation
Global economic development has been driven mainly by the availability of cheap fossil fuels such as oil and gas (Kraan 2013), essential for the production of plastics and fertilizers, which provide the energy needed for lighting, heating and transportation (Hannon et al. 2010). However, the current consumption rate is expected to result in oil depletion by the middle of this century (Kraan 2013), a consequence of continued population growth and economic expansion (Hannon et al. 2010). Most importantly, the burning of these fossil fuels over the past 100 years has led to an increase in atmospheric CO2 concentration, which is expected to rise to 450 ppm by 2020 if no action is taken by then (Kraan 2013). Alternative sources are emerging in the form of renewable options (solar, wind, water, and biofuels) but in their current form will only provide a fraction of the energy need (Kraan 2013). The International Energy Agency (IEA) estimates that biofuels will contribute 6% of total fuel consumption by 2030 (Hannon et al. 2010). Biofuels that can be produced without the need for arable land or reduced tropical forests can be very attractive in the future – algae can offer this opportunity (Darzins et al. 2010). However, microalgae biotechnology began to develop only in the middle of the last century (Darzins et al. 2010). A number of technologies have been developed and although no strategy is likely to provide a total solution, it seems possible that a combination of strategies could substantially reduce dependence on fossil fuels in a sustainable and cost-effective manner (Hannon et al. 2010).
With increasing demand for products that are capable of replacing petroleum products, and growing environmental concerns, biofuel production has received increasing attention in recent years (Posten and Schaub 2009), leading many countries looking for new cleaner and less expensive energy sources in their manufacturing cost (Chen et al. 2011). Although there is currently a greater interest in this type of energy production, first generation biofuels, made from vegetable oils (such as rapeseed oil, sugar cane, sugar beet, and maize), and animal oils and animal fat (FAO 2008) have been around for over a century (Campbell et al. 2011). However, since vegetable oils are also used for human consumption there may be an increase in the price of edible oils, causing the cost of biodiesel to increase, leading to a decrease in its use (Mata et al. 2010). The potential market for biodiesel far exceeds the availability of unassigned vegetable oils to other markets (Mata et al. 2010). For example, to meet a 10% target in the European Union, from domestic production the supply of real raw materials is not sufficient to meet the current demand, and the need for cultivation space for biofuel production would be more than the potential of arable land available for bioenergy crops (Scarlat et al. 2008).
Biofuel production through phytoplankton or microalgae appears to be the only source of biodiesel, which has the potential to completely remove fossil fuel as the main energy source (Chisti 2008). Unlike other oilseed crops, microalgae grow very fast and are extremely rich in oil and tend to double their biomass within 24 h (Chisti 2008). Compared to other renewable energy sources such as solar, hydroelectric, and tidal, biofuel production allows the energy produced to be stored and enables direct use, for example, in engines (Scott et al. 2010). The European Commission stressed the importance of consensus regarding marine biotechnology for developing policy options and new initiatives, and specifically for maritime affairs policy. The definition would need to delineate what is covered by marine biotechnology as contributing to one of the five areas (blue energy; aquaculture; maritime, coastal and cruise tourism; marine mineral resources; and marine biotechnology) of the long-term European Union (EU) strategy “Blue Growth: Opportunities for Marine and Maritime Sustainable Growth.” That strategy provides for additional effort at EU level to 2020 to stimulate long-term growth and jobs in the blue or ocean economy, in line with the objectives of the Europe 2020 strategy. In the context of the EU, important contributions were made to the development of suitable definitions in order to build a consistent Kknowledge- Bbased Bio-Economy Network in the European Commission policies and program.
Due to recent dramatic changes in oil prices and strong global concerns about climate change, biologically produced fuels have increasingly been identified as potential sources of alternative energy, reducing CO2 emissions, and, in some cases, supporting local agriculture and developing economies (Smith et al. 2009). There are considerable challenges to manufacturing biofuels that can compete with oil. Of course, a premium price is required; however, the estimated costs of an algae-based fuel barrel using current technology is $ 300–2600, compared to $ 40–80 (2009) for oil (Hannon et al. 2010). In order to become a viable alternative energy source, a biofuel must provide a positive energy balance, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supply (Smith et al. 2009). Some authors also argue that investing in biofuel production can boost the economy of developing countries (Richmond 1988; Udakis 2012). The use of micro- and macro-algae biomass for biofuel production represents one of the newest and most promising applications of marine biotechnology (Ritchie et al. 2013). Its tolerance to salt and brackish water, the ability to use a variety of organic waste as fertilizer and its growth in photobioreactors provide even more advantages (Ritchie et al. 2013). This type of biofuels has the potential to replace a significant portion of the total diesel used today, with a lower environmental impact (Darzins et al. 2010). However, there are challenges, especially in the cultivation and extraction phases of lipids. Studies states that algae-derived biodiesel production is sustainable only if implemented in a wastewater treatment plant, which would eliminate the nutrient and water needs essential for algae cultivation and if processing requirements are reduced (Kring et al. 2013). Biofuel production through phytoplankton or microalgae appears to be the only source of biodiesel, which has the potential to completely remove fossil fuel as the main source of energy (Brown et al. 1999; Muller-Feuga 2000). Microalgae biomass production is usually more expensive than food crop production, but there are currently two viable techniques for producing it: photobioreactors and raceway ponds. In addition to their use in biodiesel production, microalgae have high potential to improve the nutritional content of various food preparations and to act as probiotic agents, thus positively affecting the health of humans and animals (Stolz and Obermayer 2005).
Microalgae are unicellular, microscopic, autotrophic, photosynthetic, prokaryotic, or eukaryotic organisms. The cyanobacteria (Cyanophyceae) are considered prokaryotic microorganisms, and green algae (Chlorophyta) and diatoms (Bacillariophyta) are eukaryotic microorganisms (Li et al. 2008; Barbosa and Wijffels 2013). These organisms are present in all ecosystems of the world, in aquatic and terrestrial ecosystems (Mata et al. 2010). The classification into taxonomic groups commonly used and accepted is: Cyanophyta and Prochlorophyta, and prokaryotes (Glaucophyta, Rhodophyta, Heterokontophyta, Haptophyta, Cryptophyta, Dinophyta, Euglenophyta, Chlorarachniophyta and Chlorophyta). The most abundant groups are Diatoms (100,000 known species), Green algae (Chlorophyceae) (8000 known species), Blue green algae (Cyanophyceae) (2000 known species) and golden algae (Chrysophyceae) (1000 known species) (Mutanda et al. 2011). They occupy the base of the food chain in the open sea (Ariyadej et al. 2004), playing a very important role in primary production, serving as food for various organisms such as rotifers, copepods, daphnia, shrimp, among others (Volkman et al. 1989). They represent a wide variety of species and live in a wide range of environmental conditions (Mata et al. 2010). It is estimated that there are more than 50,000 species, but only a limited number, about 30,000, have been studied and analyzed (Richmond 2004). Using microalgae for biofuel production has many advantages, and one of those advantages is that they can grow almost anywhere, only require sunlight and some nutrients and if exponential growth is required, just add some nutrients and sandblasting so that there is an increase in its production (Pratoomyot et al. 2005). These microorganisms synthesize and accumulate large quantities of neutral lipids and can be grown on more inhospitable land such as semiarid land, provided the right conditions for good growth / development are provided, wastewater (agricultural or industrial runoff, for example) (Cohen 1986; Richmond 1990; Certik and Shimizu 1999; Brown 1991; Raven et al. 1988; Ratledge 2001; Becker 1988, 2004). The presence of excessive inorganic nutrients, such as nitrogen and phosphorus, due to anthropogenic sources, causes eutrophication in water bodies (Camargo and Alonso 2006), manifested in an increased frequency of harmful algal blooms (Liu et al. 2013). These nutrients could eventually also be used to enhance the dense growth of economically valuable aquatic plant, such as for microalgae cultivation (Kamyab et al. 2014) and can help capture the CO2 emitted by fossil fuels, helping to reduce greenhouse gas emissions, and ultimately can be used in value added products such as biopolymers (Naik et al. 2010). Over time, there has been a growing interest in the study of microorganisms such as microalgae in commercial applications in different areas such as nutrition, human and animal health, wastewater treatment, energy production, and the production of compounds, interest of the food, chemical and pharmaceutical industries, among others (Borowitzka 1999; Certik and Shimizu 1999; Kirk and Behrens 1999; Leman 1997; Bruno 2001; Grobbelaar 2004; Richmond 1990).
Microalgae as an Alternative Fuel Source
Microalgal Biomass Production
Fossil fuel reserves are increasingly depleted and the search for alternative sources of energy is therefore urgent (Harun et al. 2010; Mata et al. 2010). There are many advantages to choosing microalgae for biofuels today: (i) microalgae have rapid growth rates using non-fresh water flows as a substrate, (ii) biofuels derived from microalgae do not interfere with food safety issues (iii) biofuels obtained from microalgae are less polluting and contaminant reducing the effects of greenhouse gases, (iv) microalgae require unventilated areas and may use gas pipes as carbon source. Their exploitation as an alternative fuel is thus promising (Chisti 2008; Greenwell et al. 2009; Griffiths and Harrison 2009; Rodolfi et al. 2009; Mata et al. 2010; Mutanda et al. 2011) and also used by the pharmaceutical, cosmetic, and explosive industries (Spolaore et al. 2006). The production of biodiesel from algae is carried out by the Transesterification reactor technology (the most commonly used process for the production of biodiesel-vegetable oil + an alcohol and catalysts, obtaining biodiesel and glycerol) (Mutanda et al. 2011). The production of microalgae biomass is usually more expensive than crop production as these organisms require light, carbon dioxide, water, inorganic salts, and relatively constant temperature (should be maintained at 20–30 °C) (Chisti 2008). To minimize production costs, sunlight should be used as the main source of energy (Chisti 2008). Microalgae biomass contains about 50% carbon by dry weight (Mirón et al. 2003). Normally, this carbon is derived from carbon dioxide and by producing about 100 t of microalgal biomass, fix approximately 183 tons of carbon dioxide (Chisti 2008). Biodiesel production can potentially use carbon dioxide released from burning fossil fuels (Sawayama et al. 1995) and it is available at little or no cost in the atmosphere (Chisti 2008). Microalgal culture is one of the modern biotechnologies (Borowitzka 1999). Commercial microalgal culture is a well-established industry and microalgal feedstock has a market potential in the trillion-dollar range. The omega-3 market is estimated to be valued at USD 9.94 Billion in 2015. The Omega-3 PUFA market is segmented on the basis of its types into docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and alpha linolenic acid (ALA) (Market and markets 2016). The worldwide production in terms of quantity of various microalgae like Spirulina, Chlorella, Dunaliella, Nostoc and Aphanizomenon, etc., has been speculated in 3000, 2000, 1200, 600 and 500 t per year, respectively (Pulz and Gross 2004), and these microalgal biomass extracts are being used by various industries for its high-value chemical compounds. Recently, microalgae production of significant amounts of biomass and oil content is used as feedstock for biodiesel production and has been proposed as a potential source of renewal energy. Additionally, residual microalgal biomass can also be utilized to generate biohydrogen using anaerobic digestion, biogas, bio-ethanol, bio-methanol, bio-plastics, bio-fertilizer, medicinal value products and animal food (Tong et al. 2014; Gebreslassie et al. 2013; Gallezot 2012). For the production of biodiesel through microalgae, there are currently two methods: photobioreactors and raceway ponds (Mirón et al. 2003; Molina et al. 2010; Lucker et al. 2014). Most of the culture systems in use today are open air and relatively unsophisticated. However, over the last 50 years, great advances have been made in our understanding of the biology of the algae and in the engineering requirements of large-scale algae culture systems. This has led to the development of several types of raceway pond and closed photobioreactors which will enable the commercialization of new algae and algal products in the next decades.
Mass culture of microalgae really began to be a focus of research after 1948 at Stanford (United States of America (USA)), Essen (Germany) and Tokyo; many of these early studies are described by Burlew (1953). The first unialgal cultures were achieved by Beijerinck (1890), with Chlorella vulgaris, and the use of such cultures for studying plant physiology was developed by Warburg in the early 1900s (Warburg 1919). Interest in applied algal culture continued, especially with studies on the use of algae as photosynthetic gas exchangers for space travel and as microbial protein sources (Shelef and Soeder 1980, Venkataraman and Becker 1985; Wharton et al. 1988). Commercial large-scale culture of microalgae commenced in the early 1960s in Japan with the culture of Chlorella (Tsukada et al. 1977) followed in the early 1970s with the establishment of a Spirulina harvesting and culturing facility in Lake Texcoco, Mexico by Sosa Texcoco S.A. (Durand-Chastel 1980). In 1977 Dai Nippon Ink and Chemicals Inc. established a commercial Spirulina plant in Thailand, and by 1980, there were 46 large-scale factories in Asia producing large amounts of microalgae (mainly Chlorella) (Kawaguchi 1980; Lee 1997). Commercial production of Dunaliella salina as a source of β-carotene became the third major microalgae industry when production facilities were established by Western Biotechnology Ltd. and Betatene Ltd. in Australia in 1986. These were soon followed by other commercial plants in Israel and in the USA. As well as these algae, the large-scale production of cyanobacteria (blue–green algae) commenced in India at about the same time (Venkatamaran 1985). Thus, in a short period of about 30 years, the industry of microalgal biotechnology has grown and diversified significantly. The success of commercial large-scale production of microalgae depends on many factors, and one of these is the development of cost-effective large-scale culture systems for the algae and the development of these has been, and continues to be, a gradual process. Raceway ponds have been around since the 1950s and are designed to make a closed loop of recirculation in a container that is about 0.3 m deep, where circulation is through a wheel with different paddles (Chisti 2008). The flow is then guided around different curves by baffles that are placed in a flow channel (Chisti 2008). The paddle wheel is in constant operation to prevent biomass sedimentation at the bottom, and during the day, production is fed continuously in front of the paddle wheel (where the flow begins) so that at the end of the circuit the broth be collected (Chisti 2008). Raceway ponds are usually made of concrete or built directly on the ground and are coated with white plastic to prevent ground leakage (Chisti 2008). They are cheaper to build and require lower maintenance costs, than photobioreactors (Mata et al. 2010); however, despite their lower cost, raceway ponds are less productive with respect to the amount of algal biomass produced than photobioreactors (Chisti 2008).
Recent studies have proposed the cultivation of algae in urban wastewater for the dual purpose of waste treatment and bioenergy production from the resulting biomass. The principle is based on the fact that nutrient recycling maintains optimal C, N, and P levels in the photobioreactor (PBR), which maximizes biomass growth and increases energy returns (Selvaratnam et al. 2015). There are actually two systems that allow microalgae cultivation: open ponds and closed photobioreactors. Comparing the two systems, the open lagoon system includes a reduction in capital investment and available technology, while its disadvantages are higher cost, higher water consumption, and less flexibility in strain selection. The PBR system, on the other hand, offers greater flexibility for strain selection and lower water processing and utilization costs (Wang et al. 2015). It is also a system that does not allow gas exchange directly with the atmosphere and can allow better process control, higher biomass concentrations, and reduced contamination, while at the same time reducing evaporation and CO2 losses (Darzins et al. 2010). Unlike raceway ponds, photobioreactors are able to produce micro-algae species monocultures over long periods of time (Chisti 2008). A photobioreactor consists of a matrix of transparent straight tubes that are made of glass or plastic, and it is in this tubular matrix, also called the solar collector, that sunlight is captured (Chisti 2008). The collection tubes are usually 0.1 m in diameter (or even less) so that light does not penetrate deeper into the algal biomass broth, in order to stimulate greater biomass production (Chisti 2008). The tubular matrix, or solar collector, is glued to optimize the reception of sunlight (Molina et al. 2010; Sánchez Mirón et al. 2003). In a typical configuration, the solar tubes are all parallel to each other, always oriented north-south, and the floor under the solar collector is often painted white or covered with white plastic sheets to increase reflection (Posten and Schaub 2009). Photobioreactors need a cooling mechanism during sunlight, and often at night, since there is loss of biomass during this period due to microalgae photorespiration (Chisti 2008). To try to control the temperature inside the photobioreactors, they have already been placed in temperature-controlled greenhouses (Pulz 2001); however, it is a very expensive and rarely used procedure (Chisti 2008).
Photobioreactors Versus Raceway Ponds
It is important to compare photobioreactors and raceway ponds and try to understand which one would be most economically viable for an annual production of 100 t of algal biomass (Chisti 2008). Both techniques consume the same amount of carbon dioxide; however, photobioreactors produce a higher yield per hectare of area used for their production than raceway ponds, since the photobioreactor biomass production is about 13 times higher than the biomass produced in raceway ponds (Chisti 2008). The cost to recover the juice produced later to be transformed into oil (biodiesel) is significantly higher in raceway ponds since the biomass concentration in these is lower than in photobioreactors (Chisti 2008). Contamination control and sterilization is achievable in photobioreactors and non-raceway ponds; microalgae species control is easy to do in photobioreactors; and their population density (number of cells present) is higher than in raceway ponds. So, finally raceway ponds have a low efficiency in the use of sunlight (Borowitzka 1999).
Biodiesel produced from microalgae is technically viable. It is the only renewable biodiesel that can potentially completely remove petroleum-derived liquid fuels. However, the microalgae biodiesel production economy needs to improve substantially to become competitive with petrodiesel production, and the improvements needed to increase competitiveness seem achievable. To increase the production of microalgae at a relatively low cost, it is necessary to resort to improvements in existing technology as well as the use of genetic and metabolic engineering (Chisti 2008). Further studies with pigments are also required to accurately determine its absorption, metabolism, potential as a natural antioxidant, anti-inflammatory and antimutagenic compounds. However, phytoplankton remains largely untapped, and so far, very little progress has been made in microalgae biotechnology (Heydarizadeh et al. 2013). In addition, the increased commercial use of algae can be considered beneficial to the environment as they are photosynthetic organisms, i.e., carbon dioxide is absorbed by these organisms and thus help to limit the emission of greenhouse gases, greenhouse effect (Mata et al. 2010; Heydarizadeh et al. 2013).
It is crucial in the near future to explore opportunities to integrate biotechnology in reaping the benefits of existing potential in biological resources, biodiversity, and ecosystems to promote socio-economic and technological development. Also, encourage exchanges between research institutions, education, companies and other stakeholders, and identify partnerships that promote the progress of biotechnology activities.
Establish a national and international network with different responsibilities for the implementation of biotechnology, biodiversity programs (genetic resources) and protection legislation, such as decision-making, science, education, project implementation, production and dissemination of technologies, business, and the public to agree on milestones for the development of biotechnology.
Know the existing technical-scientific and legal basis, as well as current programs at European, South American and African level in the biotechnology forum, allowing the identification of exchange networks between researchers, decision-makers, and companies in the forum of biotechnology.
Identify and realize opportunities for cooperation and project development in the areas of biotechnology and protection of natural resources.
Promote familiarization with relevant legislation such as intellectual property protection, biosafety, and protection of natural resources.
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