Cool and Exciting Facts About Science......,,,,,,,,,, "Because Facts Are Stranger Than Fiction"
Friday, June 25, 2010
Chlorophyta: Green Algae
Chlorophyta: Green Algae
Examples: Chlorella, Chlamydomonas, Spirogyra, Ulva. Green seaweeds.
Characteristics: Green colour from chlorophyll a and b in the same proportions as the 'higher' plants; beta-carotene (a yellow pigment); and various characteristic xanthophylls (yellowish or brownish pigments). Food reserves are starch, some fats or oils like higher plants. Green algae are thought to have the progenitors of the higher green plants but there is currently some debate on this point.
Green algae may be unicellular (one cell), multicellular (many cells), colonial (living as a loose aggregation of cells) or coenocytic (composed of one large cell without cross-walls; the cell may be uninucleate or multinucleate). They have membrane-bound chloroplasts and nuclei. Most green are aquatic and are found commonly in freshwater (mainly charophytes) and marine habitats (mostly chlorophytes); some are terrestrial, growing on soil, trees, or rocks (mostly trebouxiophytes). Some are symbiotic with fungi giving lichens. Others are symbiotic with animals, e.g. the freshwater coelentrate Hydra has a symbiotic species of Chlorella as does Paramecium bursaria, a protozoan. A number of freshwater green algae (charophytes, desmids and Spirogyra) are now included in the Charophyta (charophytes), a phylum of predominantly freshwater and terrestrial algae, which are more closely related to the higher plants than the marine green algae belonging to the Chlorophyta (known as chlorophytes). Other green algae from mostly terrestrial habitats are included in the Trebouxiophyceae, a class of green algae with some very unusual features.
Asexual reproduction may be by fission (splitting), budding, fragmentation or by zoospores (motile spores). Sexual reproduction is very common and may be isogamous (gametes both motile and same size); anisogamous (both motile and different sizes - female bigger) or oogamous (female non-motile and egg-like; male motile). Many green algae have an alternation of haploid and diploid phases. The haploid phases form gametangia (sexual reproductive organs) and the diploid phases form zoospores by reduction division (meiosis). Some do not have an alternation of generations, meiosis occurring in the zygote. There are about 8,000 species of green algae, about 1,000 of which are marine chlorophytes and the remainder freshwater charophytes. Unfortunately, just because algae are green no longer means that they are related: two major aggregation of green algae, the Chlorophyta and the Charophyta have turned out not be remotely related to each other.
Commercial uses: Organic beta-carotene is produced in Australia from the hypersaline (growing in high salinity water often known as brine) green alga Dunaliella salina grown in huge ponds. Carotene has been shown to be very effective in preventing some cancers, including lung cancer. Caulerpa, a marine tropical to warm-temperate genus, is very popular in aquaria. Unfortunately, this has led to the introduction of a number of Caulerpa species around the world, the best-known example being the invasive species Caulerpa taxifolia.
Chlorella, a genus of freshwater and terrestrial unicellular green alga with about 100 species, is grown like yeast in bioreactors, where it has a very rapid life history. It may be taken in the form of tablets or capsules, or added to foods such as pasta or cookies. Taken in any form, it is said improve the nutritional quality of a daily diet. According to the Taiwan Chlorella Manufacturing Company the increase in processed and refined foods in the diet of modern man make Chlorella an important food supplement for anyone interested in better health.
Examples: Chlorella, Chlamydomonas, Spirogyra, Ulva. Green seaweeds.
Characteristics: Green colour from chlorophyll a and b in the same proportions as the 'higher' plants; beta-carotene (a yellow pigment); and various characteristic xanthophylls (yellowish or brownish pigments). Food reserves are starch, some fats or oils like higher plants. Green algae are thought to have the progenitors of the higher green plants but there is currently some debate on this point.
Green algae may be unicellular (one cell), multicellular (many cells), colonial (living as a loose aggregation of cells) or coenocytic (composed of one large cell without cross-walls; the cell may be uninucleate or multinucleate). They have membrane-bound chloroplasts and nuclei. Most green are aquatic and are found commonly in freshwater (mainly charophytes) and marine habitats (mostly chlorophytes); some are terrestrial, growing on soil, trees, or rocks (mostly trebouxiophytes). Some are symbiotic with fungi giving lichens. Others are symbiotic with animals, e.g. the freshwater coelentrate Hydra has a symbiotic species of Chlorella as does Paramecium bursaria, a protozoan. A number of freshwater green algae (charophytes, desmids and Spirogyra) are now included in the Charophyta (charophytes), a phylum of predominantly freshwater and terrestrial algae, which are more closely related to the higher plants than the marine green algae belonging to the Chlorophyta (known as chlorophytes). Other green algae from mostly terrestrial habitats are included in the Trebouxiophyceae, a class of green algae with some very unusual features.
Asexual reproduction may be by fission (splitting), budding, fragmentation or by zoospores (motile spores). Sexual reproduction is very common and may be isogamous (gametes both motile and same size); anisogamous (both motile and different sizes - female bigger) or oogamous (female non-motile and egg-like; male motile). Many green algae have an alternation of haploid and diploid phases. The haploid phases form gametangia (sexual reproductive organs) and the diploid phases form zoospores by reduction division (meiosis). Some do not have an alternation of generations, meiosis occurring in the zygote. There are about 8,000 species of green algae, about 1,000 of which are marine chlorophytes and the remainder freshwater charophytes. Unfortunately, just because algae are green no longer means that they are related: two major aggregation of green algae, the Chlorophyta and the Charophyta have turned out not be remotely related to each other.
Commercial uses: Organic beta-carotene is produced in Australia from the hypersaline (growing in high salinity water often known as brine) green alga Dunaliella salina grown in huge ponds. Carotene has been shown to be very effective in preventing some cancers, including lung cancer. Caulerpa, a marine tropical to warm-temperate genus, is very popular in aquaria. Unfortunately, this has led to the introduction of a number of Caulerpa species around the world, the best-known example being the invasive species Caulerpa taxifolia.
Chlorella, a genus of freshwater and terrestrial unicellular green alga with about 100 species, is grown like yeast in bioreactors, where it has a very rapid life history. It may be taken in the form of tablets or capsules, or added to foods such as pasta or cookies. Taken in any form, it is said improve the nutritional quality of a daily diet. According to the Taiwan Chlorella Manufacturing Company the increase in processed and refined foods in the diet of modern man make Chlorella an important food supplement for anyone interested in better health.
Cyanochloronta, Cyanobacteria, blue-green algae, blue-green bacteria.
Introduction and uniqueness
The algae are the simplest members of the plant kingdom, and the blue-green algae are the simplest of the algae. They have a considerable and increasing economic importance; they have both beneficial and harmful effects on human life. Blue-greens are not true algae. They have no nucleus, the structure that encloses the DNA, and no chloroplast, the structure that encloses the photosynthetic membranes, the structures that are evident in photosynthetic true algae. Infact blue-greens are more akin to bacteria which have similar biochemical and structural characteristics. The process of nitrogen fixation and the occurrence of gas vesicles are especially important to the success of nuisance species of blue-greens. The blue-greens are widely distributed over land and water, often in environments where no other vegetation can exist. Their fossils have been identified as over three billion years old. They were probably the chief primary producers of organic matter and the first organisms to release elemental oxygen, O2, into the primitive atmosphere, which was until then free from O2. Thus blue-greens were most probably responsible for a major evolutionary transformation leading to the development of aerobic metabolism and to the subsequent rise of higher plant and animal forms. They are referred to in literature by various names, chief among which are Cyanophyta, Myxophyta, Cyanochloronta, Cyanobacteria, blue-green algae, blue-green bacteria.
The majority of blue-greens are aerobic photoautotrophs: their life processes require only oxygen, light and inorganic substances. A species of Oscillatoria that is found in mud at the bottom of the Thames, are able to live anaerobically. They can live in extremes of temperatures -60°C to 85°C, and a few species are halophilic or salt tolerant (as high as 27%, for comparison, conc. of salt in seawater is 3%). Blue-greens can grow in full sunlight and in almost complete darkness. hey are often the first plants to colonize bare areas of rock and soil, as an example subsequent to cataclysmic volcanic explosion (at Krakatoa, Indonesia in 1883). Unlike more advanced organisms, these need no substances that have been preformed by other organisms.
At the onset of nitrogen limitation during bloom conditions, certain cells in Anabaena and Aphanizomenon evolve into heterocysts, which convert nitrogen gas into ammonium, which is then distributed to the neighboring cells of a filament. In addition, blue-greens that form symbiotic (mutually beneficial) relationships with a wide range of other life forms, can convert nitrogen gas into ammonium.
Finally, at the onset of adverse environmental conditions, some blue-greens can develop a modified cell, called an akinete. Akinetes contain large reserves of carbohydrates, and owing to their density and lack of gas vesicles, eventually settle to the lake bottom. They can tolerate adverse conditions such as the complete drying of a pond or the cold winter temperatures, and, as a consequence, akinetes serve as "seeds" for the growth of juvenile filaments when favorable conditions return. Heterocysts and akinetes are unique to the blue-greens.
Blue-greens in freshwater lakes
Unicellular and filamentous blue-greens are almost invariably present in freshwater lakes frequently forming dense planktonic populations or water blooms in eutrophic (nutrient rich) waters. In temperate lakes there is a characteristic seasonal succession of the bloom-forming species, due apparently to their differing responses to the physical- chemical conditions created by thermal stratification. Usually the filamentous forms (Anabaena species, Aphanizomenon flos-aquae and Gloeotrichia echinulata) develop first soon after the onset of stratification in late spring or early summer, while the unicellular-colonial forms (like Microcystis species) typically bloom in mid-summer or in autumn. The main factors which appear to determine the development of planktonic populations are light, temperature, pH, nutrient concentrations and the presence of organic solutes.
Attached and benthic populations in lakes
Many blue-greens grow attached on the surface of rocks and stones (epilithic forms), on submerged plants (epiphytic forms) or on the bottom sediments (epipelic forms, or the benthos) of lakes.
The epilithic community displays a clearly discernable zonation in lakes. Members of the genera Pleurocapsa, Gloeocapsa and Phormidium often dominate the dark blue-black community of the spray zone. Scytonema and Nostoc species form olive-green coatings and are more frequent about the water line, whilst the brownish Tolypothrix and Calothrix species are more typical components of the subsurface littoral community.
The epiphytic flora of lakes is usually dominated by diatoms and green algae, and blue-greens are of less importance in this community. Species of the genera Nostoc, Lyngbya, Chamaesiphon and Gloeotrichia have been occasionally encrusting submerged plants.
The epipelic community commonly includes blue-greens like Aphanothece and Nostoc particularly in the more eutrophic lakes. Benthic blue-greens growing over the littoral sediments and on submerged plants may be responsible for the occasional high rates of N2-fixation measured in oligotrophic lakes.
Terrestrial blue-greens
In the temperate region blue-greens are especially common in calcareous and alkaline soils. Certain species, Nostoc commune, are often conspicuous on the soil surface. Acid soils, however, lack blue-green element and are usually dominated by diatoms and green algae.
Gliding movement
When viewed under the light microscope, blue-greens show a variety of movements, such as gliding, rotation, oscillation, jerking and flicking.
Nuisance/Noxious Conditions
The formation of water blooms results from the redistribution and often rapid accumulation of buoyant planktonic populations. When such populations are subjected to suboptimal conditions, they respond by increasing their buoyancy and move upward nearer to the water surface. Water turbulence usually prevents them reaching the surface. If, however, turbulence suddenly weakens on a calm summer day, the buoyant population may 'over-float' and may become lodged right at the water surface. There the cells are exposed to most unfavourable and dangerous conditions, like O2 supersaturation, rapidly diminishing CO2 concentrations and intense solar radiation, which are inhibitory to photosynthesis and N2-fixation, causing photo-oxidation of pigments and inflicting irreversible damage to the genetic constitution of cells. A frequent outcome of surface bloom formation is massive cell lysis and rapid disintegration of large planktonic populations. his is closely followed by an equally rapid increase in bacterial numbers, and in turn by a fast deoxygenation of surface waters which could be detrimental to animal populations within the lake. Water blooms are objectionable for recreational activities, and more importantly, create great nuisance in the management of water reservoirs.
Most of these conditions are produced by just three blue-greens, informally referred to as Annie (Anabaena flos-aquae), Fannie (Aphanizomenon flos-aquae) and Mike (Microcystis aeroginosa). An oversupply of nutrients, especially phosphorus and possibly nitrogen, will often result in excessive growth of blue-greens because they possess certain adaptations that enable them to outcompete true algae. Perhaps the most important adaptation is their positive buoyancy, which is regulated by their gas vesicles which are absent in true algae.
Benefits
Their reputation as "nuisance" or "noxious" is totally undeserved. While periodic blooms are considered a nuisance in recreational lakes and water supply reservoirs of North America, the near continuous blooms of blue-greens in some tropical lakes are a valuable source of food for humans. Some blue-green species make major contributions to the world food supply by naturally fertilizing soils and rice paddies. R.N. Singh of the Banares Hindu University in India has shown that the introduction of blue-green algae to saline and alkaline soils in the state of Uttar Pradesh increases the soils' content of nitrogen and organic matter and also their capacity for holding water. This treatment has enabled formerly barren soils to grow crops. Astushi Watanabe of the University of Tokyo found the introduction of Tolypothrix tenuis resulted in a 20% increase of rice crop. W.E. Booth of the University of Kansas showed through experiments in Kansas, Oklahoma and Texas, that a coating of blue-greens on prairie soil binds the particles of the soil to their mucilage coating, maintains a high water content and reduces erosion.
Humans also consume Spirulina. It contains all of the amino acids essential for humans, and its protein content is high (± 60%). It is a staple food in parts of Africa and Mexico. In China, Taiwan and Japan, several blue-greens are served as a side dish and a delicacy. Several areas in North America culture and commercially process certain blue-greens for various food and medicinal products such as vitamins, drug compounds, and growth factors.
Heterocystous blue-greens possess the unique ability to simultaneously evolve O2 in photosynthesis (in vegetative cells) and H2 by nitrogenase catalyzed electron transfer to H+-ions (in heterocysts), in the absence of N2 or other substrates of nitrogenase. This is the basis for the attempts of several workers to exploit the potential through the development of a `biophotolytic system' for solar energy conversion, even though to date the thermodynamic efficiency has been disappointingly low.
Nevertheless, the utilization of blue-greens in food production and in solar energy conversion may hold immense potential for the future, and could be exploited for man's economy. Progress in the study of the genetics of blue-greens may enable us to manipulate the N2-fixation (nif) and associated genes, and produce strains which fix N2, evolve H2 or release ammonia with great efficiency.
Poisonous Conditions
(Also see, Diverse taxa of cyanobacteria produce ß-N-methylamino-L-alanine (BMAA), a neurotoxic amino acid- Proc. the National Academy of Sciences of the USA, 2005) Poisonous blue-greens occur in ponds and lakes throughout the world. In Canada, they primarily occur in the prairie provinces. Poisoning has caused the death of cows, dogs, and other animals. Although humans ordinarily avoid drinking water that displays a blue-green bloom or scum, they may be affected by toxic strains when they swim or ski in recreational water bodies during a bloom. Typical symptoms include redness of the skin and itching around the eyes; sore, red throat; headache; diarrhea; vomiting; and nausea. The frequently occurring `swimmers itch' is attributed to contact with Lyngbya majuscula, Schizothrix calcicola and Oscillatoria nigroviridis, which are commonly found in tropical and subtropical seawaters. The toxins responsible are lipid-soluble phenolic compounds. Since the same or similar symptoms can be produced by bacteria or viruses, one should not necessarily conclude that blue-greens are responsible for a human illness simply because the sick individual recently swam in a lake or pond that has suffered a bloom. Human death has not been documented. Reported cases affecting humans list Anabaena as the main culprit.
Most of the recorded toxic blooms are caused by Microcystis aeruginosa, which manufactures "microcystin", which yields 7 (or 14) amino acids upon hydrolysis. It causes enlargement and congestion of the liver followed by necrosis and haemorrhage, and may also exhibit neurotoxic activity.
But many toxic blooms are also produced by either Anabaena flos-aquae (manufactures "anatoxins") or Aphanizomenon flos-aquae (manufactures "aphantoxins").
Alkaloid toxins (anatoxins, aphantoxins) act on the nervous system, leading to paralysis of muscles needed for breathing.
Two other genera, Oscillatoria and Nodularia are also known to produce toxic populations. Whether the animal survives the poisoning depends primarily upon the concentration of toxin ingested. Blue-green toxins may act on zooplankton and might be an effective mechanism of protection against grazing pressures.
Little is known about the percent of blooms that are toxic (upto 25% quoted in literature), and also why a toxic population is produced. A complicating factor is that part of a bloom can be toxic and another part nontoxic within the same lake. It has been suggested that toxic strains may develop only under a particular set of environmental conditions, or that toxin production may be associated with plasmid-mediated gene transfer.
Colour and identification
The blue-green color of cells (cyan means blue-green) is due to the combination of green chlorophyll pigment and a unique blue pigment (phycocyanin). However, not all blue-greens are blue-green. Their pigmentation includes yellow-green, green, grey-green, grey-black, and even red specimens. The Red Sea derives its name from occasional blooms of a species of Oscillatoria that produces large quantities of a unique pigment called phycoerythrin. In the arid regions of Central and East Africa, flamingos consume vast quantities of Spirulina, and their feathers derive their pink color from carotene pigments in filaments of Spirulina.
The blue-greens are microscopic life forms that exhibit several different types of organization. Some grow as single cells enclosed in a sheath of slime-like material, or mucilage. The cells of others aggregate into colonies that are either flattened, cubed, rounded, or elongated into filaments. Actual identification of cyanobacteria (blue-greens) requires microscopic examination of cells, colonies, or filaments, although experienced aquatic biologists can usually recognize Microcystis (colonies look like tiny grey-green clumps) and Aphanizomenon (green, fingernail-like or grass-like clippings).
Measures to control the growth of blue-greens
Chemicals are widely used to prevent the growth of nuisance algae, and the commonest one being copper sulphate. A number of other algicides are phenolic compounds, amide derivatives, quaternary ammonium compounds and quinone derivatives. Dichloron aphthoquinone is selectively toxic to blue-greens. The hazards of using toxic chemicals indiscriminately in the natural environment are well documented.
Biological control is in principle possible, though not always practical and as effective. Invertebrates like cladocerans, copepods, ostracods and snails are known to graze on green algae and diatoms. Daphnia pulex has been reported to feed on Aphanizomenon flos-aquae while present in the form of single filaments or small colonies but avoid large raft-like colonies. The copepod Diaptomus has been implicated in the grazing of Anabaena populations in Severson Lake, Minnesota.
Micro-organisms (fungi, bacteria and viruses) appear to play an important part in regulating growth of blue-greens in freshwaters. Certain chytrids (fungal pathogens) specifically infest akinetes, other heterocysts. Bacterial pathogens belonging to the group of Myxobacteriales can effect rapid lysis of a wide range of unicellular and filamentous blue-greens, though heterocysts and akinetes remain generally unaffected. Viral pathogens belonging to the group of cyanophages exhibit some degree of host specifity. Phage AR-1 attacks Anabaenopsis, phages SM-1 and AS-1 are effective against the unicellular forms, Synechococcus and Microcystis, Phage C-1 lyses Cylindropermum, and the LPP-1 virus is effective against strains of Lyngbya, Phormidium and Plectonema.
The long-term approach is no doubt the systematic removal of major nutrients.
The algae are the simplest members of the plant kingdom, and the blue-green algae are the simplest of the algae. They have a considerable and increasing economic importance; they have both beneficial and harmful effects on human life. Blue-greens are not true algae. They have no nucleus, the structure that encloses the DNA, and no chloroplast, the structure that encloses the photosynthetic membranes, the structures that are evident in photosynthetic true algae. Infact blue-greens are more akin to bacteria which have similar biochemical and structural characteristics. The process of nitrogen fixation and the occurrence of gas vesicles are especially important to the success of nuisance species of blue-greens. The blue-greens are widely distributed over land and water, often in environments where no other vegetation can exist. Their fossils have been identified as over three billion years old. They were probably the chief primary producers of organic matter and the first organisms to release elemental oxygen, O2, into the primitive atmosphere, which was until then free from O2. Thus blue-greens were most probably responsible for a major evolutionary transformation leading to the development of aerobic metabolism and to the subsequent rise of higher plant and animal forms. They are referred to in literature by various names, chief among which are Cyanophyta, Myxophyta, Cyanochloronta, Cyanobacteria, blue-green algae, blue-green bacteria.
The majority of blue-greens are aerobic photoautotrophs: their life processes require only oxygen, light and inorganic substances. A species of Oscillatoria that is found in mud at the bottom of the Thames, are able to live anaerobically. They can live in extremes of temperatures -60°C to 85°C, and a few species are halophilic or salt tolerant (as high as 27%, for comparison, conc. of salt in seawater is 3%). Blue-greens can grow in full sunlight and in almost complete darkness. hey are often the first plants to colonize bare areas of rock and soil, as an example subsequent to cataclysmic volcanic explosion (at Krakatoa, Indonesia in 1883). Unlike more advanced organisms, these need no substances that have been preformed by other organisms.
At the onset of nitrogen limitation during bloom conditions, certain cells in Anabaena and Aphanizomenon evolve into heterocysts, which convert nitrogen gas into ammonium, which is then distributed to the neighboring cells of a filament. In addition, blue-greens that form symbiotic (mutually beneficial) relationships with a wide range of other life forms, can convert nitrogen gas into ammonium.
Finally, at the onset of adverse environmental conditions, some blue-greens can develop a modified cell, called an akinete. Akinetes contain large reserves of carbohydrates, and owing to their density and lack of gas vesicles, eventually settle to the lake bottom. They can tolerate adverse conditions such as the complete drying of a pond or the cold winter temperatures, and, as a consequence, akinetes serve as "seeds" for the growth of juvenile filaments when favorable conditions return. Heterocysts and akinetes are unique to the blue-greens.
Blue-greens in freshwater lakes
Unicellular and filamentous blue-greens are almost invariably present in freshwater lakes frequently forming dense planktonic populations or water blooms in eutrophic (nutrient rich) waters. In temperate lakes there is a characteristic seasonal succession of the bloom-forming species, due apparently to their differing responses to the physical- chemical conditions created by thermal stratification. Usually the filamentous forms (Anabaena species, Aphanizomenon flos-aquae and Gloeotrichia echinulata) develop first soon after the onset of stratification in late spring or early summer, while the unicellular-colonial forms (like Microcystis species) typically bloom in mid-summer or in autumn. The main factors which appear to determine the development of planktonic populations are light, temperature, pH, nutrient concentrations and the presence of organic solutes.
Attached and benthic populations in lakes
Many blue-greens grow attached on the surface of rocks and stones (epilithic forms), on submerged plants (epiphytic forms) or on the bottom sediments (epipelic forms, or the benthos) of lakes.
The epilithic community displays a clearly discernable zonation in lakes. Members of the genera Pleurocapsa, Gloeocapsa and Phormidium often dominate the dark blue-black community of the spray zone. Scytonema and Nostoc species form olive-green coatings and are more frequent about the water line, whilst the brownish Tolypothrix and Calothrix species are more typical components of the subsurface littoral community.
The epiphytic flora of lakes is usually dominated by diatoms and green algae, and blue-greens are of less importance in this community. Species of the genera Nostoc, Lyngbya, Chamaesiphon and Gloeotrichia have been occasionally encrusting submerged plants.
The epipelic community commonly includes blue-greens like Aphanothece and Nostoc particularly in the more eutrophic lakes. Benthic blue-greens growing over the littoral sediments and on submerged plants may be responsible for the occasional high rates of N2-fixation measured in oligotrophic lakes.
Terrestrial blue-greens
In the temperate region blue-greens are especially common in calcareous and alkaline soils. Certain species, Nostoc commune, are often conspicuous on the soil surface. Acid soils, however, lack blue-green element and are usually dominated by diatoms and green algae.
Gliding movement
When viewed under the light microscope, blue-greens show a variety of movements, such as gliding, rotation, oscillation, jerking and flicking.
Nuisance/Noxious Conditions
The formation of water blooms results from the redistribution and often rapid accumulation of buoyant planktonic populations. When such populations are subjected to suboptimal conditions, they respond by increasing their buoyancy and move upward nearer to the water surface. Water turbulence usually prevents them reaching the surface. If, however, turbulence suddenly weakens on a calm summer day, the buoyant population may 'over-float' and may become lodged right at the water surface. There the cells are exposed to most unfavourable and dangerous conditions, like O2 supersaturation, rapidly diminishing CO2 concentrations and intense solar radiation, which are inhibitory to photosynthesis and N2-fixation, causing photo-oxidation of pigments and inflicting irreversible damage to the genetic constitution of cells. A frequent outcome of surface bloom formation is massive cell lysis and rapid disintegration of large planktonic populations. his is closely followed by an equally rapid increase in bacterial numbers, and in turn by a fast deoxygenation of surface waters which could be detrimental to animal populations within the lake. Water blooms are objectionable for recreational activities, and more importantly, create great nuisance in the management of water reservoirs.
Most of these conditions are produced by just three blue-greens, informally referred to as Annie (Anabaena flos-aquae), Fannie (Aphanizomenon flos-aquae) and Mike (Microcystis aeroginosa). An oversupply of nutrients, especially phosphorus and possibly nitrogen, will often result in excessive growth of blue-greens because they possess certain adaptations that enable them to outcompete true algae. Perhaps the most important adaptation is their positive buoyancy, which is regulated by their gas vesicles which are absent in true algae.
Benefits
Their reputation as "nuisance" or "noxious" is totally undeserved. While periodic blooms are considered a nuisance in recreational lakes and water supply reservoirs of North America, the near continuous blooms of blue-greens in some tropical lakes are a valuable source of food for humans. Some blue-green species make major contributions to the world food supply by naturally fertilizing soils and rice paddies. R.N. Singh of the Banares Hindu University in India has shown that the introduction of blue-green algae to saline and alkaline soils in the state of Uttar Pradesh increases the soils' content of nitrogen and organic matter and also their capacity for holding water. This treatment has enabled formerly barren soils to grow crops. Astushi Watanabe of the University of Tokyo found the introduction of Tolypothrix tenuis resulted in a 20% increase of rice crop. W.E. Booth of the University of Kansas showed through experiments in Kansas, Oklahoma and Texas, that a coating of blue-greens on prairie soil binds the particles of the soil to their mucilage coating, maintains a high water content and reduces erosion.
Humans also consume Spirulina. It contains all of the amino acids essential for humans, and its protein content is high (± 60%). It is a staple food in parts of Africa and Mexico. In China, Taiwan and Japan, several blue-greens are served as a side dish and a delicacy. Several areas in North America culture and commercially process certain blue-greens for various food and medicinal products such as vitamins, drug compounds, and growth factors.
Heterocystous blue-greens possess the unique ability to simultaneously evolve O2 in photosynthesis (in vegetative cells) and H2 by nitrogenase catalyzed electron transfer to H+-ions (in heterocysts), in the absence of N2 or other substrates of nitrogenase. This is the basis for the attempts of several workers to exploit the potential through the development of a `biophotolytic system' for solar energy conversion, even though to date the thermodynamic efficiency has been disappointingly low.
Nevertheless, the utilization of blue-greens in food production and in solar energy conversion may hold immense potential for the future, and could be exploited for man's economy. Progress in the study of the genetics of blue-greens may enable us to manipulate the N2-fixation (nif) and associated genes, and produce strains which fix N2, evolve H2 or release ammonia with great efficiency.
Poisonous Conditions
(Also see, Diverse taxa of cyanobacteria produce ß-N-methylamino-L-alanine (BMAA), a neurotoxic amino acid- Proc. the National Academy of Sciences of the USA, 2005) Poisonous blue-greens occur in ponds and lakes throughout the world. In Canada, they primarily occur in the prairie provinces. Poisoning has caused the death of cows, dogs, and other animals. Although humans ordinarily avoid drinking water that displays a blue-green bloom or scum, they may be affected by toxic strains when they swim or ski in recreational water bodies during a bloom. Typical symptoms include redness of the skin and itching around the eyes; sore, red throat; headache; diarrhea; vomiting; and nausea. The frequently occurring `swimmers itch' is attributed to contact with Lyngbya majuscula, Schizothrix calcicola and Oscillatoria nigroviridis, which are commonly found in tropical and subtropical seawaters. The toxins responsible are lipid-soluble phenolic compounds. Since the same or similar symptoms can be produced by bacteria or viruses, one should not necessarily conclude that blue-greens are responsible for a human illness simply because the sick individual recently swam in a lake or pond that has suffered a bloom. Human death has not been documented. Reported cases affecting humans list Anabaena as the main culprit.
Most of the recorded toxic blooms are caused by Microcystis aeruginosa, which manufactures "microcystin", which yields 7 (or 14) amino acids upon hydrolysis. It causes enlargement and congestion of the liver followed by necrosis and haemorrhage, and may also exhibit neurotoxic activity.
But many toxic blooms are also produced by either Anabaena flos-aquae (manufactures "anatoxins") or Aphanizomenon flos-aquae (manufactures "aphantoxins").
Alkaloid toxins (anatoxins, aphantoxins) act on the nervous system, leading to paralysis of muscles needed for breathing.
Two other genera, Oscillatoria and Nodularia are also known to produce toxic populations. Whether the animal survives the poisoning depends primarily upon the concentration of toxin ingested. Blue-green toxins may act on zooplankton and might be an effective mechanism of protection against grazing pressures.
Little is known about the percent of blooms that are toxic (upto 25% quoted in literature), and also why a toxic population is produced. A complicating factor is that part of a bloom can be toxic and another part nontoxic within the same lake. It has been suggested that toxic strains may develop only under a particular set of environmental conditions, or that toxin production may be associated with plasmid-mediated gene transfer.
Colour and identification
The blue-green color of cells (cyan means blue-green) is due to the combination of green chlorophyll pigment and a unique blue pigment (phycocyanin). However, not all blue-greens are blue-green. Their pigmentation includes yellow-green, green, grey-green, grey-black, and even red specimens. The Red Sea derives its name from occasional blooms of a species of Oscillatoria that produces large quantities of a unique pigment called phycoerythrin. In the arid regions of Central and East Africa, flamingos consume vast quantities of Spirulina, and their feathers derive their pink color from carotene pigments in filaments of Spirulina.
The blue-greens are microscopic life forms that exhibit several different types of organization. Some grow as single cells enclosed in a sheath of slime-like material, or mucilage. The cells of others aggregate into colonies that are either flattened, cubed, rounded, or elongated into filaments. Actual identification of cyanobacteria (blue-greens) requires microscopic examination of cells, colonies, or filaments, although experienced aquatic biologists can usually recognize Microcystis (colonies look like tiny grey-green clumps) and Aphanizomenon (green, fingernail-like or grass-like clippings).
Measures to control the growth of blue-greens
Chemicals are widely used to prevent the growth of nuisance algae, and the commonest one being copper sulphate. A number of other algicides are phenolic compounds, amide derivatives, quaternary ammonium compounds and quinone derivatives. Dichloron aphthoquinone is selectively toxic to blue-greens. The hazards of using toxic chemicals indiscriminately in the natural environment are well documented.
Biological control is in principle possible, though not always practical and as effective. Invertebrates like cladocerans, copepods, ostracods and snails are known to graze on green algae and diatoms. Daphnia pulex has been reported to feed on Aphanizomenon flos-aquae while present in the form of single filaments or small colonies but avoid large raft-like colonies. The copepod Diaptomus has been implicated in the grazing of Anabaena populations in Severson Lake, Minnesota.
Micro-organisms (fungi, bacteria and viruses) appear to play an important part in regulating growth of blue-greens in freshwaters. Certain chytrids (fungal pathogens) specifically infest akinetes, other heterocysts. Bacterial pathogens belonging to the group of Myxobacteriales can effect rapid lysis of a wide range of unicellular and filamentous blue-greens, though heterocysts and akinetes remain generally unaffected. Viral pathogens belonging to the group of cyanophages exhibit some degree of host specifity. Phage AR-1 attacks Anabaenopsis, phages SM-1 and AS-1 are effective against the unicellular forms, Synechococcus and Microcystis, Phage C-1 lyses Cylindropermum, and the LPP-1 virus is effective against strains of Lyngbya, Phormidium and Plectonema.
The long-term approach is no doubt the systematic removal of major nutrients.
Green Algae
The term 'algae' is used for some lower plants and many, often unrelated groups of microorganisms that are able to perform photosynthesis.
Photosynthesis (converting light energy into chemical energy) is performed in parts of the cell called chloroplasts. They can be found in different shapes and colours and in many different organisms. Not all these organisms are green. Diatoms, Chrysophytes and dinoflagellates have yellow to brown chloroplasts. There are brown algae (Phaeophyta), red algae (Rhodophyta) and many other groups of unicellular algae in many shades of green. The blue green Cyanobacteria also photosynthesize.
A very diverse groups of freshwater algae are the Chlorophytes or Green algae. Based on the compounds of the photosynthetic pigments and several other characteristics they seem closest related to plants.
A common green algae is Hydrodictyon, the water net. It is a related to Pediastrum (top image) But it forms a bag-shaped colony. Like Pediastrum each individual cell can develop into a new colony. You can imagine that since the colony contains thousands of cells Hydrodictyon can reproduce very rapidly. And unlike Pediastrum, Hydrodictyon can grow large, almost 30 cm. in length. Blooms of Hydrodictyon can be a real problem for water treatment plants.
The image shows a part of a small colony (left) and three individual cells of a big colony. Inside each of these cells a new colony can be formed.
This species illustrates that green algae don't always have to look like green algae. The chloroplast often turns red when conditions become unfavourable. Haematococcus swims with the aid of two long flagella.
Many species are flagellated and motile, other are immobile but often have a flagellated stage at some time in their life cycle. Certainly one of the most spectacular flagellated green algae is Volvox. It forms a spherical colony. All the small cells of the colony possess two flagella and a small eyespot. With this the colony is able to swim towards the light. Volvox has interesting ways of reproduction.
A small rather inconspicuous green algae without undulipodia is Chlorella. It can be found as an endosymbiont inside ciliates, hydra and other animals. They raise Chlorella as if they grow crops in a greenhouse.
The close up of this green Paramecium bursaria, a ciliate, shows the individual cells of Chlorella.
Many green algae form long filaments. The cells stay attached after they divide. Some genera, like Spirogyra, Mougeotia and Zygnema can become so numerous they form dense mats of growth in surfaces of ponds, so-called pond scum. This pond scum is interesting for a study under the microscope. If you squeeze it in a jar you will collect many interesting organisms. And the filamentous algae are at least as interesting. The chloroplasts have distinct shapes. In Spirogyra the chloroplast runs through the cell like a helix. The image also shows the nucleus hanging on fine threads.
Spirogyra and related algae like the Desmids are conjugating green algae. These desmids are so beautiful they deserve a page for themselves.
Algae fuel
Algae fuel
Algae fuel, also called algal fuel, algaeoleum or second-generation biofuel,[1] is a biofuel which is derived from algae. During photosynthesis, algae and other photosynthetic organisms capture carbon dioxide and sunlight and convert it into oxygen and biomass. Up to 99% of the carbon dioxide in solution can be converted, which was shown by Weissman and Tillett (1992) in large-scale open-pond systems. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable.[2] The production of biofuels from algae does not reduce atmospheric carbon dioxide (CO2), because any CO2 taken out of the atmosphere by the algae is returned when the biofuels are burned. They do however eliminate the introduction of new CO2[citation needed] by displacing fossil hydrocarbon fuels.
High oil prices, competing demands between foods and other biofuel sources, and the world food crisis, have ignited interest in algaculture (farming algae) for making vegetable oil, biodiesel, bioethanol, biogasoline, biomethanol, biobutanol and other biofuels, using land that is not suitable for agriculture. Among algal fuels' attractive characteristics: they do not affect fresh water resources,[3] can be produced using ocean and wastewater, and are biodegradable and relatively harmless to the environment if spilled.[4][5][6] Algae cost more per unit mass (as of 2010, food grade algae costs ~$5000/tonne), due to high capital and operating costs[7], yet can theoretically yield between 10 and 100 times more energy per unit area than other, second-generation biofuel crops.[8] One biofuels company has claimed that algae can produce more oil in an area the size of a two car garage than a football field of soybeans, because almost the entire algal organism can use sunlight to produce lipids, or oil.[9] The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (40,000 km2).[10] This is less than 1⁄7 the area of corn harvested in the United States in 2000.[11] However, these claims remain unrealized, commercially.
Factors
Dry mass factor is the percentage of dry biomass in relation to the fresh biomass; e.g. if the dry mass factor is 5%, one would need 20 kg of wet algae (algae in the media) to get 1 kg of dry algae cells.[12]
Lipid content is the percentage of oil in relation to the dry biomass needed to get it, i.e. if the algae lipid content is 40%, one would need 2.5 kg of dry algae to get 1 kg of oil.[13]
Fuels
The vegoil algae product can then be harvested and converted into biodiesel; the algae’s carbohydrate content can be fermented into bioethanol and biobutanol.[14]
Biodiesel
Currently most research into efficient algal-oil production is being done in the private sector, but predictions from small scale production experiments bear out that using algae to produce biodiesel may be the only viable method by which to produce enough automotive fuel to replace current world diesel usage.[15]
Microalgae have much faster growth rates than terrestrial crops. The per unit area yield of oil from algae is estimated to be from between 5,000 to 20,000 US gallons per acre per year (4,700 to 18,000 m3/km2·a);[citation needed] this is 7 to 30 times greater than the next best crop, Chinese tallow (700 US gal/acre·a or 650 m3/km2·a).[16]
Studies[17] show that some species of algae can produce up to 60% of their dry weight in the form of oil. Because the cells grow in aqueous suspension, where they have more efficient access to water, CO2 and dissolved nutrients, microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photobioreactors. This oil can then be turned into biodiesel which could be sold for use in automobiles. Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities.[18]
Biobutanol
Main article: Butanol fuel
Butanol can be made from algae or diatoms using only a solar powered biorefinery. This fuel has an energy density 10% less than gasoline, and greater than that of either ethanol or methanol. In most gasoline engines, butanol can be used in place of gasoline with no modifications. In several tests, butanol consumption is similar to that of gasoline, and when blended with gasoline, provides better performance and corrosion resistance than that of ethanol or E85[19].
The green waste left over from the algae oil extraction can be used to produce butanol.
Biogasoline
Biogasoline is gasoline produced from biomass such as algae. Like traditionally produced gasoline, it contains between 6 (hexane) and 12 (dodecane) carbon atoms per molecule and can be used in internal-combustion engines.
Methane
Through the use of algaculture grown organisms and cultures, various polymeric materials can be broken down into methane.[20]
SVO
The algal-oil feedstock that is used to produce biodiesel can also be used for fuel directly as "Straight Vegetable Oil", (SVO). The benefit of using the oil in this manner is that it doesn't require the additional energy needed for transesterification, (processing the oil with an alcohol and a catalyst to produce biodiesel). The drawback is that it does require modifications to a normal diesel engine. Transesterified biodiesel can be run in an unmodified modern diesel engine, provided the engine is designed to use ultra-low sulfur diesel, which, as of 2006, is the new diesel fuel standard in the United States.
Hydrocracking to traditional transport fuels
Main articles: Vegetable oil refining and Green crude
Vegetable oil can be used as feedstock for an oil refinery where methods like hydrocracking or hydrogenation can be used to transform the vegetable oil into standard fuels like gasoline and diesel.[21]
Jet fuel
Main article: Aviation biofuel
Rising jet fuel prices are putting severe pressure on airline companies,[22] creating an incentive for algal jet fuel research. The International Air Transport Association, for example, supports research, development and deployment of algal fuels. IATA’s goal is for its members to be using 10% alternative fuels by 2017.[1]
Trials have been carried with aviation biofuel by Air New Zealand[23], Continental Airlines[citation needed] and Virgin Airlines[24].
In February 2010, the Defense Advanced Research Projects Agency announced that the U.S. military was about to begin large-scale production oil from algal ponds into jet fuel. After extraction at a cost of $2 per gallon, the oil will be refined at less than $3 a gallon. A larger-scale refining operation, producing 50 million gallons a year, is expected to go into production in 2013, with the possibility of lower per gallon costs so that algae-based fuel would be competitive with fossil fuels. The projects, run by the companies SAIC and General Atomics, are expected to produce 1,000 gallons of oil per acre per year from algal ponds.[25]
Algae cultivation
Algae can produce up to 300 times more oil per acre than conventional crops, such as rapeseed, palms, soybeans, or jatropha. As Algae has a harvesting cycle of 1–10 days, it permits several harvests in a very short time frame, a differing strategy to yearly crops (Chisti 2007). Algae can also be grown on land that is not suitable for other established crops, for instance, arid land, land with excessively saline soil, and drought-stricken land. This minimizes the issue of taking away pieces of land from the cultivation of food crops (Schenk et al. 2008). Algae can grow 20 to 30 times faster than food crops.[26]
Photobioreactors
Most companies pursuing algae as a source of biofuels are pumping nutrient-laden water through plastic tubes (called "bioreactors" ) that are exposed to sunlight (and so called photobioreactors or PBR).
Running a PBR is more difficult than an open pond, and more costly.
Algae can also grow on marginal lands, such as in desert areas where the groundwater is saline, rather than utilize fresh water.[27]
Because algae strains with lower lipid content may grow as much as 30 times faster than those with high lipid content,[28] the difficulties in efficient biodiesel production from algae lie in finding an algal strain with a combination of high lipid content and fast growth rate, that isn't too difficult to harvest; and a cost-effective cultivation system (i.e., type of photobioreactor) that is best suited to that strain. There is also a need to provide concentrated CO2 to increase the rate of production.
[edit] Closed loop system
Another obstacle preventing widespread mass production of algae for biofuel production has been the equipment and structures needed to begin growing algae in large quantities. Maximum use of existing agriculture processes and hardware is the goal.[29]
In a closed system (not exposed to open air) there is not the problem of contamination by other organisms blown in by the air. The problem for a closed system is finding a cheap source of sterile CO2. Several experimenters have found the CO2 from a smokestack works well for growing algae.[30][31] To be economical, some experts think that algae farming for biofuels will have to be done as part of cogeneration, where it can make use of waste heat, and help soak up pollution.[27][32]
[edit] Open pond
Open-pond systems for the most part have been given up for the cultivation of algae with high-oil content.[33] Many believe that a major flaw of the Aquatic Species Program was the decision to focus their efforts exclusively on open-ponds; this makes the entire effort dependent upon the hardiness of the strain chosen, requiring it to be unnecessarily resilient in order to withstand wide swings in temperature and pH, and competition from invasive algae and bacteria. Open systems using a monoculture are also vulnerable to viral infection. The energy that a high-oil strain invests into the production of oil is energy that is not invested into the production of proteins or carbohydrates, usually resulting in the species being less hardy, or having a slower growth rate. Algal species with a lower oil content, not having to divert their energies away from growth, have an easier time in the harsher conditions of an open system.
Some open sewage ponds trial production has been done in Marlborough, New Zealand.[34]
[edit] Algae types
Main article: SERI microalgae culture collection
Research into algae for the mass-production of oil is mainly focused on microalgae; organisms capable of photosynthesis that are less than 0.4 mm in diameter, including the diatoms and cyanobacteria; as opposed to macroalgae, such as seaweed. The preference towards microalgae is due largely to its less complex structure, fast growth rate, and high oil content (for some species). However, some research is being done into using seaweeds for biofuels, probably due to the high availability of this resource.[35][36]
The following species listed are currently being studied for their suitability as a mass-oil producing crop, across various locations worldwide[37][38][39]:
Botryococcus braunii
Chlorella
Dunaliella tertiolecta
Gracilaria
Pleurochrysis carterae (also called CCMP647)[40] .
Sargassum, with 10 times the output volume of Gracilaria.[41]
In addition, due to its high growth rate, Ulva[42] has been investigated as a fuel for use in the SOFT cycle, (SOFT stands for Solar Oxygen Fuel Turbine), a closed-cycle power generation system suitable for use in arid, subtropical regions.[43]
[edit] Specific research
Some commercial interests into large scale algal-cultivation systems are looking to tie in to existing infrastructures, such as cement factories,[32] coal power plants, or sewage treatment facilities. This approach changes wastes into resources to provide the raw materials, CO2 and nutrients, for the system.[44]
Aquaflow Bionomic Corporation of New Zealand announced that it has produced its first sample of homegrown bio-diesel fuel with algae sourced from local sewerage ponds. A small quantity of laboratory produced oil was mixed with 95% regular diesel.
A feasibility study using marine microalgae in a photobioreactor is being done by The International Research Consortium on Continental Margins at the International University Bremen.[45]
The Department of Environmental Science at Ateneo de Manila University in the Philippines, is working on producing biofuel from a local species of algae.[46]
NBB’s Feedstock Development program is addressing production of algae on the horizon to expand available material for biodiesel in a sustainable manner[47].
[edit] Nutrients
Main article: Algal nutrient solutions
Nutrients like nitrogen (N), phosphorus (P), and potassium (K), are important for plant growth and are essential parts of fertilizer. Silica and iron, as well as several trace elements, may also be considered important marine nutrients as the lack of one can limit the growth of, or productivity in, an area.[48]
One company, Green Star Products, announced their development of a micronutrient formula to increase the growth rate of algae. According to the company, its formula can increase the daily growth rate by 34% and can double the amount of algae produced in one growth cycle.[49]
Wastewater
Wastewater treatment facility
A possible nutrient source is waste water from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks. However, this waste water cannot feed algae directly and must first be processed by bacteria, through anaerobic digestion. If waste water is not processed before it reaches the algae, it will contaminate the algae in the reactor, and at the very least, kill much of the desired algae strain. In biogas facilities, organic waste is often converted to a mixture of carbon dioxide, methane, and organic fertilizer. Organic fertilizer that comes out of the digester is liquid, and nearly suitable for algae growth, but it must first be cleaned and sterilized.
The utilization of wastewater and ocean water instead of freshwater is strongly advocated due to the continuing depletion of freshwater resources. However, heavy metals, trace metals, and other contaminants in wastewater can decrease the ability of cells to produce lipids biosynthetically and also impact various other workings in the machinery of cells. The same is true for ocean water, but the contaminants are found in different concentrations. Thus, agricultural-grade fertilizer is the preferred source of nutrients, but heavy metals are again a problem, especially for strains of algae that are susceptible to these metals. In open pond systems the use of strains of algae that can deal with high concentrations of heavy metals could prevent other organisms from infesting these systems (Schenk et al. 2008). In some instances it has even been shown that strains of algae can remove over 90% of nickel and zinc from industrial wastewater in relatively short periods of time (Chong, Wong et al. 1998).
Investment and economic viability
There is always uncertainty about the success of new products and investors have to consider carefully the proper energy sources in which to invest. A drop in fossil fuel oil prices might make consumers and therefore investors lose interest in renewable energy. Algal fuel companies are learning that investors have different expectations about returns and length of investments. AlgaePro Systems found in its talks with investors that while one wants at least 5 times the returns on their investment, others would only be willing to invest in a profitable operation over the long term. Every investor has its own unique stipulations that are obstacles to further algae fuel development. Additional concerns consider the potential environmental impact of Algal fuel development, as well as secondary impacts on wildlife such as bears and fish.[citation needed]
Whereas technical problems, such as harvesting, are being addressed successfully by the industry, the high up-front investment of algae-to-biofuels facilities is seen by many as a major obstacle to the success of this technology. Only few studies on the economic viability are publicly available, and must often rely on the little data (often only engineering estimates) available in the public domain. Dmitrov[50] examined the GreenFuels photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel. A study by Alabi at al.[51] examined raceways, photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels. Raceways might be cost-effective in warm climates with very low labor costs, and fermenters may become cost-effective subsequent to significant process improvements. The group found that capital cost, labor cost and operational costs (fertilizer, electricity, etc.) by themselves are too high for algae biofuels to be cost-competitive with conventional fuels. Similar results were found by others[52][53][54], suggesting that unless new, cheaper ways of harnessing algae for biofuels production are found, their great technical potential may never become economically accessible.
Algae fuel by country
List of algal fuel producers
Europe
Algae fuel in the United Kingdom
Universities in the United Kingdom which are working on producing oil from algae include:University of Glasgow, University of Brighton, Cambridge University, University College London, Imperial College London, Cranfield University.
The Ukraine plans to produce biofuel using a special type of algae[55].
The CSIC´s Instituto de Bioquímica Vegetal y Fotosíntesis (Microalgae Biotechnology Group, in Sevilla, Spain[56] is researching the algal fuels.
United States
Algae fuel in the United States
The Aquatic Species Program, launched in 1978, was a research program funded by the United States Department of Energy (DoE) which was tasked with investigating the use of algae for the production of energy. The program initially focused efforts on the production of hydrogen, shifting primary research to studying oil production in 1982. From 1982 until its end in 1996, the majority of the program research was focused on the production of transportation fuels, notably biodiesel, from algae. In 1995, as part of overall efforts to lower budget demands, the DoE decided to end the program. Research stopped in 1996 and staff began compiling their research for publication.
US universities which are working on producing oil from algae include: University of Texas at Austin,[57] University of Maine, University of Kansas, and Old Dominion University[58].
At the Woods Hole Oceanographic Institution and the Harbor Branch Oceanographic Institution the wastewater from domestic and industrial sources contain rich organic compounds that are being used to accelerate the growth of algae.[14] The Department of Biological and Agricultural Engineering at University of Georgia is exploring microalgal biomass production using industrial wastewater.[59] Algaewheel, based in Indianapolis, Indiana, presented a proposal to build a facility in Cedar Lake, Indiana that uses algae to treat municipal wastewater, using the sludge byproduct to produce biofuel.[60][61]
Sapphire Energy (San Diego) has produced green crude from algae.
Solazyme (South San Francisco, California) has produced a fuel suitable for powering jet aircraft from algae.
Algae fuel, also called algal fuel, algaeoleum or second-generation biofuel,[1] is a biofuel which is derived from algae. During photosynthesis, algae and other photosynthetic organisms capture carbon dioxide and sunlight and convert it into oxygen and biomass. Up to 99% of the carbon dioxide in solution can be converted, which was shown by Weissman and Tillett (1992) in large-scale open-pond systems. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable.[2] The production of biofuels from algae does not reduce atmospheric carbon dioxide (CO2), because any CO2 taken out of the atmosphere by the algae is returned when the biofuels are burned. They do however eliminate the introduction of new CO2[citation needed] by displacing fossil hydrocarbon fuels.
High oil prices, competing demands between foods and other biofuel sources, and the world food crisis, have ignited interest in algaculture (farming algae) for making vegetable oil, biodiesel, bioethanol, biogasoline, biomethanol, biobutanol and other biofuels, using land that is not suitable for agriculture. Among algal fuels' attractive characteristics: they do not affect fresh water resources,[3] can be produced using ocean and wastewater, and are biodegradable and relatively harmless to the environment if spilled.[4][5][6] Algae cost more per unit mass (as of 2010, food grade algae costs ~$5000/tonne), due to high capital and operating costs[7], yet can theoretically yield between 10 and 100 times more energy per unit area than other, second-generation biofuel crops.[8] One biofuels company has claimed that algae can produce more oil in an area the size of a two car garage than a football field of soybeans, because almost the entire algal organism can use sunlight to produce lipids, or oil.[9] The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (40,000 km2).[10] This is less than 1⁄7 the area of corn harvested in the United States in 2000.[11] However, these claims remain unrealized, commercially.
Factors
Dry mass factor is the percentage of dry biomass in relation to the fresh biomass; e.g. if the dry mass factor is 5%, one would need 20 kg of wet algae (algae in the media) to get 1 kg of dry algae cells.[12]
Lipid content is the percentage of oil in relation to the dry biomass needed to get it, i.e. if the algae lipid content is 40%, one would need 2.5 kg of dry algae to get 1 kg of oil.[13]
Fuels
The vegoil algae product can then be harvested and converted into biodiesel; the algae’s carbohydrate content can be fermented into bioethanol and biobutanol.[14]
Biodiesel
Currently most research into efficient algal-oil production is being done in the private sector, but predictions from small scale production experiments bear out that using algae to produce biodiesel may be the only viable method by which to produce enough automotive fuel to replace current world diesel usage.[15]
Microalgae have much faster growth rates than terrestrial crops. The per unit area yield of oil from algae is estimated to be from between 5,000 to 20,000 US gallons per acre per year (4,700 to 18,000 m3/km2·a);[citation needed] this is 7 to 30 times greater than the next best crop, Chinese tallow (700 US gal/acre·a or 650 m3/km2·a).[16]
Studies[17] show that some species of algae can produce up to 60% of their dry weight in the form of oil. Because the cells grow in aqueous suspension, where they have more efficient access to water, CO2 and dissolved nutrients, microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photobioreactors. This oil can then be turned into biodiesel which could be sold for use in automobiles. Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities.[18]
Biobutanol
Main article: Butanol fuel
Butanol can be made from algae or diatoms using only a solar powered biorefinery. This fuel has an energy density 10% less than gasoline, and greater than that of either ethanol or methanol. In most gasoline engines, butanol can be used in place of gasoline with no modifications. In several tests, butanol consumption is similar to that of gasoline, and when blended with gasoline, provides better performance and corrosion resistance than that of ethanol or E85[19].
The green waste left over from the algae oil extraction can be used to produce butanol.
Biogasoline
Biogasoline is gasoline produced from biomass such as algae. Like traditionally produced gasoline, it contains between 6 (hexane) and 12 (dodecane) carbon atoms per molecule and can be used in internal-combustion engines.
Methane
Through the use of algaculture grown organisms and cultures, various polymeric materials can be broken down into methane.[20]
SVO
The algal-oil feedstock that is used to produce biodiesel can also be used for fuel directly as "Straight Vegetable Oil", (SVO). The benefit of using the oil in this manner is that it doesn't require the additional energy needed for transesterification, (processing the oil with an alcohol and a catalyst to produce biodiesel). The drawback is that it does require modifications to a normal diesel engine. Transesterified biodiesel can be run in an unmodified modern diesel engine, provided the engine is designed to use ultra-low sulfur diesel, which, as of 2006, is the new diesel fuel standard in the United States.
Hydrocracking to traditional transport fuels
Main articles: Vegetable oil refining and Green crude
Vegetable oil can be used as feedstock for an oil refinery where methods like hydrocracking or hydrogenation can be used to transform the vegetable oil into standard fuels like gasoline and diesel.[21]
Jet fuel
Main article: Aviation biofuel
Rising jet fuel prices are putting severe pressure on airline companies,[22] creating an incentive for algal jet fuel research. The International Air Transport Association, for example, supports research, development and deployment of algal fuels. IATA’s goal is for its members to be using 10% alternative fuels by 2017.[1]
Trials have been carried with aviation biofuel by Air New Zealand[23], Continental Airlines[citation needed] and Virgin Airlines[24].
In February 2010, the Defense Advanced Research Projects Agency announced that the U.S. military was about to begin large-scale production oil from algal ponds into jet fuel. After extraction at a cost of $2 per gallon, the oil will be refined at less than $3 a gallon. A larger-scale refining operation, producing 50 million gallons a year, is expected to go into production in 2013, with the possibility of lower per gallon costs so that algae-based fuel would be competitive with fossil fuels. The projects, run by the companies SAIC and General Atomics, are expected to produce 1,000 gallons of oil per acre per year from algal ponds.[25]
Algae cultivation
Algae can produce up to 300 times more oil per acre than conventional crops, such as rapeseed, palms, soybeans, or jatropha. As Algae has a harvesting cycle of 1–10 days, it permits several harvests in a very short time frame, a differing strategy to yearly crops (Chisti 2007). Algae can also be grown on land that is not suitable for other established crops, for instance, arid land, land with excessively saline soil, and drought-stricken land. This minimizes the issue of taking away pieces of land from the cultivation of food crops (Schenk et al. 2008). Algae can grow 20 to 30 times faster than food crops.[26]
Photobioreactors
Most companies pursuing algae as a source of biofuels are pumping nutrient-laden water through plastic tubes (called "bioreactors" ) that are exposed to sunlight (and so called photobioreactors or PBR).
Running a PBR is more difficult than an open pond, and more costly.
Algae can also grow on marginal lands, such as in desert areas where the groundwater is saline, rather than utilize fresh water.[27]
Because algae strains with lower lipid content may grow as much as 30 times faster than those with high lipid content,[28] the difficulties in efficient biodiesel production from algae lie in finding an algal strain with a combination of high lipid content and fast growth rate, that isn't too difficult to harvest; and a cost-effective cultivation system (i.e., type of photobioreactor) that is best suited to that strain. There is also a need to provide concentrated CO2 to increase the rate of production.
[edit] Closed loop system
Another obstacle preventing widespread mass production of algae for biofuel production has been the equipment and structures needed to begin growing algae in large quantities. Maximum use of existing agriculture processes and hardware is the goal.[29]
In a closed system (not exposed to open air) there is not the problem of contamination by other organisms blown in by the air. The problem for a closed system is finding a cheap source of sterile CO2. Several experimenters have found the CO2 from a smokestack works well for growing algae.[30][31] To be economical, some experts think that algae farming for biofuels will have to be done as part of cogeneration, where it can make use of waste heat, and help soak up pollution.[27][32]
[edit] Open pond
Open-pond systems for the most part have been given up for the cultivation of algae with high-oil content.[33] Many believe that a major flaw of the Aquatic Species Program was the decision to focus their efforts exclusively on open-ponds; this makes the entire effort dependent upon the hardiness of the strain chosen, requiring it to be unnecessarily resilient in order to withstand wide swings in temperature and pH, and competition from invasive algae and bacteria. Open systems using a monoculture are also vulnerable to viral infection. The energy that a high-oil strain invests into the production of oil is energy that is not invested into the production of proteins or carbohydrates, usually resulting in the species being less hardy, or having a slower growth rate. Algal species with a lower oil content, not having to divert their energies away from growth, have an easier time in the harsher conditions of an open system.
Some open sewage ponds trial production has been done in Marlborough, New Zealand.[34]
[edit] Algae types
Main article: SERI microalgae culture collection
Research into algae for the mass-production of oil is mainly focused on microalgae; organisms capable of photosynthesis that are less than 0.4 mm in diameter, including the diatoms and cyanobacteria; as opposed to macroalgae, such as seaweed. The preference towards microalgae is due largely to its less complex structure, fast growth rate, and high oil content (for some species). However, some research is being done into using seaweeds for biofuels, probably due to the high availability of this resource.[35][36]
The following species listed are currently being studied for their suitability as a mass-oil producing crop, across various locations worldwide[37][38][39]:
Botryococcus braunii
Chlorella
Dunaliella tertiolecta
Gracilaria
Pleurochrysis carterae (also called CCMP647)[40] .
Sargassum, with 10 times the output volume of Gracilaria.[41]
In addition, due to its high growth rate, Ulva[42] has been investigated as a fuel for use in the SOFT cycle, (SOFT stands for Solar Oxygen Fuel Turbine), a closed-cycle power generation system suitable for use in arid, subtropical regions.[43]
[edit] Specific research
Some commercial interests into large scale algal-cultivation systems are looking to tie in to existing infrastructures, such as cement factories,[32] coal power plants, or sewage treatment facilities. This approach changes wastes into resources to provide the raw materials, CO2 and nutrients, for the system.[44]
Aquaflow Bionomic Corporation of New Zealand announced that it has produced its first sample of homegrown bio-diesel fuel with algae sourced from local sewerage ponds. A small quantity of laboratory produced oil was mixed with 95% regular diesel.
A feasibility study using marine microalgae in a photobioreactor is being done by The International Research Consortium on Continental Margins at the International University Bremen.[45]
The Department of Environmental Science at Ateneo de Manila University in the Philippines, is working on producing biofuel from a local species of algae.[46]
NBB’s Feedstock Development program is addressing production of algae on the horizon to expand available material for biodiesel in a sustainable manner[47].
[edit] Nutrients
Main article: Algal nutrient solutions
Nutrients like nitrogen (N), phosphorus (P), and potassium (K), are important for plant growth and are essential parts of fertilizer. Silica and iron, as well as several trace elements, may also be considered important marine nutrients as the lack of one can limit the growth of, or productivity in, an area.[48]
One company, Green Star Products, announced their development of a micronutrient formula to increase the growth rate of algae. According to the company, its formula can increase the daily growth rate by 34% and can double the amount of algae produced in one growth cycle.[49]
Wastewater
Wastewater treatment facility
A possible nutrient source is waste water from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks. However, this waste water cannot feed algae directly and must first be processed by bacteria, through anaerobic digestion. If waste water is not processed before it reaches the algae, it will contaminate the algae in the reactor, and at the very least, kill much of the desired algae strain. In biogas facilities, organic waste is often converted to a mixture of carbon dioxide, methane, and organic fertilizer. Organic fertilizer that comes out of the digester is liquid, and nearly suitable for algae growth, but it must first be cleaned and sterilized.
The utilization of wastewater and ocean water instead of freshwater is strongly advocated due to the continuing depletion of freshwater resources. However, heavy metals, trace metals, and other contaminants in wastewater can decrease the ability of cells to produce lipids biosynthetically and also impact various other workings in the machinery of cells. The same is true for ocean water, but the contaminants are found in different concentrations. Thus, agricultural-grade fertilizer is the preferred source of nutrients, but heavy metals are again a problem, especially for strains of algae that are susceptible to these metals. In open pond systems the use of strains of algae that can deal with high concentrations of heavy metals could prevent other organisms from infesting these systems (Schenk et al. 2008). In some instances it has even been shown that strains of algae can remove over 90% of nickel and zinc from industrial wastewater in relatively short periods of time (Chong, Wong et al. 1998).
Investment and economic viability
There is always uncertainty about the success of new products and investors have to consider carefully the proper energy sources in which to invest. A drop in fossil fuel oil prices might make consumers and therefore investors lose interest in renewable energy. Algal fuel companies are learning that investors have different expectations about returns and length of investments. AlgaePro Systems found in its talks with investors that while one wants at least 5 times the returns on their investment, others would only be willing to invest in a profitable operation over the long term. Every investor has its own unique stipulations that are obstacles to further algae fuel development. Additional concerns consider the potential environmental impact of Algal fuel development, as well as secondary impacts on wildlife such as bears and fish.[citation needed]
Whereas technical problems, such as harvesting, are being addressed successfully by the industry, the high up-front investment of algae-to-biofuels facilities is seen by many as a major obstacle to the success of this technology. Only few studies on the economic viability are publicly available, and must often rely on the little data (often only engineering estimates) available in the public domain. Dmitrov[50] examined the GreenFuels photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel. A study by Alabi at al.[51] examined raceways, photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels. Raceways might be cost-effective in warm climates with very low labor costs, and fermenters may become cost-effective subsequent to significant process improvements. The group found that capital cost, labor cost and operational costs (fertilizer, electricity, etc.) by themselves are too high for algae biofuels to be cost-competitive with conventional fuels. Similar results were found by others[52][53][54], suggesting that unless new, cheaper ways of harnessing algae for biofuels production are found, their great technical potential may never become economically accessible.
Algae fuel by country
List of algal fuel producers
Europe
Algae fuel in the United Kingdom
Universities in the United Kingdom which are working on producing oil from algae include:University of Glasgow, University of Brighton, Cambridge University, University College London, Imperial College London, Cranfield University.
The Ukraine plans to produce biofuel using a special type of algae[55].
The CSIC´s Instituto de Bioquímica Vegetal y Fotosíntesis (Microalgae Biotechnology Group, in Sevilla, Spain[56] is researching the algal fuels.
United States
Algae fuel in the United States
The Aquatic Species Program, launched in 1978, was a research program funded by the United States Department of Energy (DoE) which was tasked with investigating the use of algae for the production of energy. The program initially focused efforts on the production of hydrogen, shifting primary research to studying oil production in 1982. From 1982 until its end in 1996, the majority of the program research was focused on the production of transportation fuels, notably biodiesel, from algae. In 1995, as part of overall efforts to lower budget demands, the DoE decided to end the program. Research stopped in 1996 and staff began compiling their research for publication.
US universities which are working on producing oil from algae include: University of Texas at Austin,[57] University of Maine, University of Kansas, and Old Dominion University[58].
At the Woods Hole Oceanographic Institution and the Harbor Branch Oceanographic Institution the wastewater from domestic and industrial sources contain rich organic compounds that are being used to accelerate the growth of algae.[14] The Department of Biological and Agricultural Engineering at University of Georgia is exploring microalgal biomass production using industrial wastewater.[59] Algaewheel, based in Indianapolis, Indiana, presented a proposal to build a facility in Cedar Lake, Indiana that uses algae to treat municipal wastewater, using the sludge byproduct to produce biofuel.[60][61]
Sapphire Energy (San Diego) has produced green crude from algae.
Solazyme (South San Francisco, California) has produced a fuel suitable for powering jet aircraft from algae.
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