Classification of Algae

The classification of algae into taxonomic groups is based upon the same rules that are used for the classification of land plants, but the organization of groups of algae above the order level has changed substantially since 1960. Research using electron microscopes has demonstrated differences in features, such as the flagellar apparatus, cell division process, and organelle structure and function, that are important in the classification of algae. Similarities and differences among algal, fungal, and protozoan groups have led scientists to propose major taxonomic changes, and these changes are continuing.

Division-level classification, as with kingdom-level classification, is tenuous for algae. For example, some phycologists place the classes Bacillariophyceae, Phaeophyceae, and Xanthophyceae in the division Chromophyta, whereas others place each class in separate divisions: Bacillariophyta, Phaeophyta, and Xanthophyta. Yet, almost all phycologists agree on the definition of the respective classes Bacillariophyceae, Phaeophyceae, and Xanthophyceae.

The classes are distinguished by the structure of flagellate cells (e.g., scales, angle of flagellar insertion, microtubular roots, and striated roots), the nuclear division process (mitosis), the cytoplasmic division process (cytokinesis), and the cell covering. Many scientists combine the Micromonadophyceae with the Pleurastrophyceae, naming the combined group the Prasinophyceae.  “Phylum” and “division” represent the same level of organization; the former is the zoological term, the latter is the botanical term

Properties of Major Algal Taxonomic Groups

S.No

Taxonomic Group

Chlorophyll

Carotenoids Bilo

proteins

Storage products

Flagellation &Cell structure

1. Bacillariophyta a, c β-carotene

± -carotene rarely fucoxanthin,.

Chrysolaminarin

oils

1 apical flagellum in male gametes:

cell in two halves with elaborate

markings.

2. Chloro

phycophyta

(green algae)

a, b β-carotene,

± -carotene

rarely carotene

and lycopene,

Starch, oils 1,2,4 to many,

equal, apical or

subapical flagella.

lutein.

3. Chrysophycophyta

(golden algae)

a, c , β-carotene,

fucoxanthin

Chrysolaminarin

oils

1 or 2 unequal, apical flagella, in some, cell surface covered by characteristic scales.

4. Cyanobacteria

(blue green algae)

a,c β-carotene,

phycobilins

5. Phaeco

phycophyta

(brown algae)

a,c β-carotene, ±

fucoxanthin,

violaxanthin

Laminarin, soluble

carbohydrates, oils

2 lateral flagella

6. Dinophyta

(dinpflagellates)

a,c β-carotene,

peridinin,

neoperididnin

dinoxanthin,

neodinoxanthin.

Starch, oils 2 lateral, 1 trailing,1 girdling flagellum, in most, there

is a longitudinal

and transverse

furrow and angular plates.

7. Rhodo

phycophyta

(red algae )

a, rarely d β-carotene, zeaxanthin

± β carotene

Phyco

erythrin

phyco

cyanin

Floridean starch

oils

Flagella absent

Properties of Algae

When cultivating algae, several factors must be considered, and different algae have different requirements. Essential factors include water, carbon dioxide, minerals and light .The algae basically consist of the plant-like organisms (particularly, they are chloroplast-containing eucaryotes) that for the most part live in the sea, but also in freshwater as well as moist terrestrial habitats and as lichen endosymbionts.

Size and StructureA thallus is the body of the vegetative form of algae. For single-celled algae, the thallus is just the single cell. For multi-celled algae, the thallus consists of the entire, continuous organism.There also exist complex algae that superficially appear to be macroscopic, multicellular organisms but, upon closer inspection, are found to actually consist of one giant, coenocytic (single celled) thallus.The aquatic habitat is a relatively benign and unchanging place, and its properties helped shape the organisms that live there. Because water supports the algal plant body, most algae lack rigidity, and usually undulate gently with water currents and waves. Since water surrounds the plant on all sides, individual algal cells absorb moisture and minerals directly from the surrounding. Plant shape also reflects this direct contact with water: Most algae are quite flattened, which maximizes the surface area for absorbing water, minerals, and sunlight.

    Mostly photosynthetic     Photosynthetic pigments- four different kinds of chlorophyll     accessory pigments- a variety, including blue, red, brown, golden     Require moist environments (lack a waxy cuticle found in terrestrial plants)     May be microscopic and float in surface waters (phytoplankton) or macroscopic and live

attached to rocky coasts (seaweeds)     Size ranges from size of bacteria (0.5 um) to over 50 m long (1 um = 1/25,000th inch; 1 m = 39

inches)

TemperatureThe water must be in a temperature range that will support the specific algal species being grown. Temperature vary with the species and strain cultured.  The optimal Temperature for phytoplankton cultures is generally between 20 and 30º C. Temperatures lower than 16 º C slow down growth; Temperatures higher than 35 º C are lethal for a number of species

Light and MixingLight must not be too strong nor too weak. In most algal-cultivation systems, light only penetrates the top 3 inches (7.6 cm) to 4 inches (10 cm) of the water. This is because as the algae grow and multiply, they become so dense that they block light from reaching deeper into the pond or tank. Algae only need about 1/10th the amount of light they receive from direct sunlight. Direct sunlight is often too strong for algae.

In order to have ponds that are deeper than 4 inches algae growers use various methods to agitate the water in their ponds, thus circulating the algae so that it does not remain on the surface, which would cause it to be over-exposed. Paddle wheels can be used to circulate (stir) the water in a pond. Compressed air can be introduced into the bottom of a pond or tank to agitate the water, bringing algae from the lower levels up with it as it makes its way to the surface.

Apart from agitation, another means of supplying light to algae is to place the light in the system. Glow plates are sheets of plastic or glass that can be submerged into a tank, providing light directly to the algae at the right concentration.

Where do Algae Grow? - Algae Growth Environments

Algae are some of the most robust organisms on earth, able to grow in a wide range of conditions.

Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, tropical regions than dry ones, because algae lack vascular tissues and other adaptions to live on land

As mentioned above, algea grow in almost every habitat in every part of the world. The following are examples of non-marine habitats.

Animals: Reported substrates include turtles, snails, rotifers, worms, crustacean, alligators, three-toed sloths, aquatic ferns, freshwater sponges and some other animals.

Aquatic plants: Algae grow on and inside water plants (including other algae) Artificial substrates: Wooden posts and fences, cans and bottles etc. all provide algal

habitats. Billabongs & lagoons: Rich microalgal habitats, particularly for desmids. Bogs, marshes & swamps Farm Dams Hot springs Lakes Mud and sand Ponds (ephemeral), puddles, roadside ditches and rock pools Reservoirs Rivers Rock (internal & surface) Saline Lagoons Saline Lakes & Marshes Salt marshes and salt lakes Sewage Soil Streams Terrestrial plants - tree trunks, branches, shady sides of trees, damp walls, surface of and inside

leaves.

Cultivation of Algae in Open Ponds Cultivation of algae in open ponds has been extensively studied. Open ponds can be categorized

into natural waters (lakes, lagoons, ponds) and artificial ponds or containers. The most commonly used systems include shallow big ponds, tanks, circular ponds and raceway ponds. One of the major advantages of open ponds is that they are easier to construct and operate than most closed systems. However, major limitations in open ponds include poor light utilization by the cells, evaporative losses, diffusion of CO2 to the atmosphere, and requirement of large areas of land. Furthermore, contamination by predators and other fast growing heterotrophs have restricted the commercial production of algae in open culture systems to only those organisms that can grow under extreme conditions. Also, due to inefficient stirring mechanisms in open cultivation systems, their mass transfer rates are very poor resulting to low biomass productivity. The ponds in which the algae are cultivated are usually what are called the “raceway ponds”. In these ponds, the algae, water & nutrients circulate around a racetrack. With paddlewheels providing the flow, algae are kept suspended in the water, and are circulated back to the surface on a regular frequency. The ponds are usually kept shallow because the algae need to be exposed to sunlight, and sunlight can only penetrate the pond water to a limited depth. The ponds are operated in a continuous manner, with CO2 and nutrients being constantly fed to the ponds, while algae-containing water is removed at the other end.

The biggest advantage of these open ponds is their simplicity, resulting in low production costs and low operating costs. While this is indeed the simplest of all the growing techniques, it has some drawbacks owing to the fact that the environment in and around the pond is not completely under control. Bad weather can stunt algae growth. Contamination from strains of bacteria or other outside organisms often results in undesirable species taking over the desired algae growing in the pond. The water in which the algae grow also has to be kept at a certain temperature, which can be difficult to maintain. Another drawback is the uneven light intensity and distribution within the pond.

The NREL’s Aquatic Species Program (ASP) used open ponds for its experiments and has also favoured the same for the future primarily owing to its economic value. However, many companies today are trying out with Closed Pond systems and in many cases, with the much more expensive photobioreactors.

Cultivation of Algae in Closed Ponds An alternative to open ponds are closed ponds where the control over the environment is much

better than that for the open ponds. Closed Pond systems cost more than the open ponds, and considerably less than photobioreactors for similar areas of operation.

As a variation of the open pond system, the idea behind the closed pond is to close it off, to cover a pond or pool with a greenhouse. While this usually results in a smaller system, it does take care of many of the problems associated with an open system. It allows more species to be grown, it allows the species that are being grown to stay dominant, and it extends the growing season, only slightly if unheated, and if heated it can produce year round. It is also possible to increase the amount of carbon-di-oxide in these quasi-closed systems, thus again increasing the rate of growth of algae.

Usually closed ponds are used in spirullina cultivation . These Closed systems are constructed using plexiglass.

Extraction of Algal Oil by Chemical Methods

Algal oil can be extracted using chemicals. Benzene and ether have been used, oil can also be separated by hexane extraction, which is widely used in the food industry and is relatively inexpensive. The downside to using solvents for oil extraction are the dangers involved in working with the chemicals. Care must be taken to avoid exposure to vapors and direct contact with the skin, either of which can cause serious damage. Benzene is classified as a carcinogen. Chemical Solvents also present the problem of being an explosion hazard.

Chemical methods include:

Hexane Solvent Method Soxhlet extraction Supercritical fluid Extraction 

Hexane Solvent Method

Algal oil can be extracted using chemicals. Benzene and ether have been used, but a popular chemical for solvent extraction is hexane, which is relatively inexpensive. The downside to using solvents for oil extraction are the inherent dangers involved in working with the chemicals. Benzene is classified as a carcinogen. Chemical solvents also present the problem of being an explosion hazard.

Hexane solvent extraction can be used in isolation or it can be used along with the oil press/expeller method. After the oil has been extracted using an expeller, the remaining pulp can be mixed with cyclo-hexane to extract the remaining oil content. The oil dissolves in the cyclohexane, and the pulp is filtered out from the solution. The oil and cyclohexane are separated by means of distillation. These two stages (cold press & hexane solvent) together will be able to derived more than 95% of the total oil present in the algae.Soxhlet Extraction

Soxhlet extraction is an extraction method that uses chemical solvents. Oils from the algae are extracted through repeated washing, or percolation, with an organic solvent such as hexane or petroleum ether, under reflux in a special glassware.

Supercritical Fluid Extraction

In supercritical fluid/CO2 extraction, CO2 is liquefied under pressure and heated to the point that it has the properties of both a liquid and a gas, this liquified fluid then acts as the solvent in extracting the oil.

Extraction of Algal Oil by Mechanical Methods

Mechanical methods includes

Expression/Expeller press Ultrasonic-assisted extraction

The simplest method is mechanical crushing. Since different strains of algae vary widely in their physical attributes, various press configurations (screw, expeller, piston, etc) work better for specific algae types. Often, mechanical crushing is used in conjunction with chemicals.

Expression/Expeller press:

Algae is dried it retains its oil content, which then can be "pressed" out with an oil press. Since different strains of algae vary widely in their physical attributes, various press configurations (screw, expeller, piston, etc) work better for specific algae types. Many commercial manufacturers of vegetable oil use a combination of mechanical pressing and Chemical Solvents in extracting oil.

Ultrasonic-assisted Extraction:

Ultrasonic extraction, a branch of Sonochemistry can greatly accelerate extraction processes. Using an ultrasonic reactor, ultrasonic waves are used to create cavitation bubbles in a solvent material, when these bubbles collapse near the cell walls, it creates shock waves and liquid jets that causes those cells walls to break and release their contents into the solvent.

Algae Oil Information

Micro-algae are the fastest growing photosynthesizing unicellular organisms and can complete an entire growing cycle every few days. Some algae species have high oil content (up to 60% oil by weight) and can produce up to 15,000 gallons of oil per Acre per year under optimum conditions.

One of the key reasons why algae are considered as feedstock for oil is their yields. Put simply, algae are the only biofeedstock that can theoretically replace all of our petro-fuel consumption of today and future. Owing to the fact that oil yields are much lower for other feedstocks when compared to those from algae, it will be very difficult for the first generation Biodiesel feedstock such as soy or palm to produce enough oil to replace even a small fraction of petro-oil needs without displacing large percentages of arable land towards crops for fuel production.Comparison of Biodiesel from Microalgal Oil and Diesel FuelProperties Biodiesel   from

Microalgal OilDiesel   Fuel

Density Kg l-1 0.864 0.838Viscosity Pa s 5.2×10-4 (40 ºC) 1.9 - 4.1 ×10-4 (40 ºC)Flash point ºC 65-115* 75Solidifying point ºC -12 -50 - 10Cold filter plugging point ºC -11 -3.0 (- 6.7 max)Acid value mg KOH g-1 0.374 0.5 maxHeating value MJ kg-1 41 40 - 45HC ratio 1.18 1.18

*: Based on data from multiple sources

Algal Oil Yields

Microalgae, like higher plants, produce storage Lipids in the form of triacyglycerols (TAGs). Comparatively algae produce more oil than any other oilseeds which are currently in use. Many microalgal species can be induced to accumulate substantial quantities of lipids, often greater than 60% of their biomass.

 Comparison of average oil yields from algae with that from other oilseeds 

The table below presents indicative oil yields from various oilseeds and algae. Please note that there are significant variations in yields even within an individual oilseed depending on where it is grown, the specific variety/grade of the plant etc. Similarly, for algae there are significant variations between oil yields from different strains of algae. The data presented below are indicative in nature, primarily to highlight the order-of-magnitude differences present in the oil yields from algae when compared with other oilseeds. (See also: Vegetable Oils Yields & Characteristics – from Journey to Forever)

     Gallons of oil per acre per year

Corn 18Soybeans 48Safflower 83Sunflower 102Rapeseed 127Oil Palm 635Micro Algae 5000-15000

Source: http://oakhavenpc.org/cultivating_algae.htm

The key question in everyone’s mind is: which is the best species of algae for biodiesel? The decades-long research undertaken by NREL of USA – called the Aquatic Species Program (see a copy of the Aquatic Species Program Research notes here, but please remembers it is a large PDF file!) suggested few high-oil-containing algae strains.

The strains of Algae most favoured by the NREL researchers were Chlorophyceae (green algae). Green algae tend to produce starch, rather than lipids. Green algae have very high growth rates at 30oC. The other algae favoured by NREL researchers are diatoms. However, the Diatoms needs silicon in the water to grow, whereas green algae requires nitrogen to grow

The following species listed are currently being studied for their suitability as a mass-oil producing crop, across various locations worldwide.

· Botryococcus braunii – This can produce long chain hydrocarbons representing 86% of its dry weight. The green alga Botryococcus is unique in the quality and quantity of the liquid hydrocarbons it produces. Some scientists consider the ancestors of Botryococcus to be responsible for many of the world's fossil fuel deposits.

· Neochloris oleoabundans - Neochloris oleoabundans is a microalga belonging in the class Chlorophyceae, a class of green algae. It has lipid content of 35 – 54% dry weight.

· Scenedesmus dimorphus - A unicellular algae in the class Chlorophyceae. While this is one of the preferred species for Oil Yield for Biodiesel one of the problems with Scenedesmus is that it's heavy, and forms thick sediments if not kept in constant agitation.

· Euglena gracilis - Euglena has a lipid content of 14-20% by dry weight. The ASP Program of NREL noted that “Euglena is unique compared to most algae of interest to the ASP as potential producers of biodiesel. Euglena produces both lipid (primarily in form of the wax ester myristyl-miristate) and carbohydrate as storage products.”

· Nannochloropsis salina – This is also called Nannochloris oculata. Nannochloropsis is small green algae that are extensively used in the Aquaculture industry for growing small zooplankton such as rotifers and for Greenwater.

· Dunaliella tertiolecta - This strain is reported to have Oil Yield of about 37% (organic basis). D. tertiolecta is a fast growing strain and that means it has a high CO2 sequestration rate as well.

· Tetraselmis chui - Tetraselmis chui is a marine unicellular alga. Tetraselmis spp. is large green flagellates with a very high lipid level. They contain natural amino acids that stimulate feeding in marine animals. They are an excellent feed for larval shrimp.

· Isochrysis galbana - Isochrysis is a small golden/brown flagellate that is very commonly used in the aquaculture industry. It is high in DHA and often used to enrich zooplankton such as rotifers or Artemia.

· Phaeodactylum tricornutum

· Pleurochrysis carterae

· Prymnesium parvum

· Tetraselmis suecica  

· Spirulina species

The lipid and fatty acid contents of Microalgae vary in accordance with culture conditions. Microalgae are known to accumulate more lipids in nutrient deficient conditions. Researchers identified the most dramatic increases in the lipid content of the cultures during N-deficient conditions. Biochemical studies have also suggested that acetyl-CoA carboxylase (ACCase), a biotin-containing enzyme that catalyzes an early step in fatty acid biosynthesis, may be involved in the control of this lipid accumulation process. Therefore, it may be possible to enhance lipid production rates by increasing the activity of this enzyme via genetic engineering. 

Biodiesel Production from Algae Oil

Algal oil is highly viscous, with viscosities ranging 10–20 times those of no. 2 Diesel fuel. The high viscosity is due to the large molecular mass and chemical structure of oils which in turn leads to problems

in pumping, combustion and atomization in the injector systems of a diesel engine. Therefore, a reduction in viscosity is important to make high-viscous oil a suitable alternative fuel for diesel engines.

There are a number of ways to reduce vegetable oil's viscosity. These methods include; transestrification, pyrolysis (Pyrolysis Definition from AFR), micro Emulsion (Emulsions & Emulsification – from Wikipedia), blending and thermal depolymerization. One of the most common methods used to reduce oil viscosity in the Biodiesel industry is called transesterification. It involves chemical conversion of the oil into its corresponding fatty ester.

Transesterification

The process of converting vegetable & plant oils into biodiesel fuel is called transesterification, and is fortunately much less complex than it sounds.

Transesterification refers to a reaction between an ester of one alcohol and a second alcohol to form an ester of the second alcohol and an alcohol from the original ester, as that of methyl acetate and ethyl alcohol to form ethyl acetate and methyl alcohol ( see also interesterification. Chemically, transesterification means taking a triglyceride molecule or a complex fatty acid, neutralizing the free fatty acids, removing the glycerin and creating an alcohol ester. This is accomplished by mixing methanol with sodium hydroxide to make sodium methoxide. This liquid is then mixed into vegetable oil. The entire mixture then settles. Glycerin is left on the bottom and methyl esters, or biodiesel, is left on top. The glycerin can be used to make soap (or any one of 1600 other products) and the methyl esters is washed and filtered.

Transesterification is not a new process. Scientists E. Duy and J. Patrick conducted it as early as 1853. One of the first uses of transesterified vegetable oil was powering heavy-duty vehicles in South Africa before World War II.

Transesterification of Algal Oil into Biodiesel

Transesterification of algal oil is normally done with Ethanol and sodium ethanolate serving as the catalyst. Sodium ethanolate can be produced by reacting ethanol with sodium.

Thus, with sodium ethanolate as the catalyst, ethanol is reacted with the algal oil ( the triglyceride) to produce bio-diesel & glycerol. The end products of this reaction are hence biodiesel, sodium ethanolate and glycerol.

This end-mixture is separated as follows: Ether and salt water are added to the mixture and mixed well. After sometime, the entire mixture would have separated into two layers, with the bottom layer containing a mixture of ether and biodiesel. This layer is separated.

Large-scale Biodiesel Production from Algae

Theoretically, Biodiesel produced from algae appears to be the only feasible solution today for replacing petro-diesel completely. No other feedstock has the Oil Yield high enough for it to be in a position to produce such large volumes of oil. To elaborate, it has been calculated that in order for a crop such as soybean or palm to yield enough oil capable of replacing petro-diesel completely, a very large percentage of the current land available needs to be utilized only for biodiesel crop production, which is quite infeasible. For some small countries, in fact it implies that all land available in the country be dedicated to biodiesel crop production. However,

if the feedstock were to be algae, owing to its very high yield of oil per Acre of cultivation, it has been found that about 10 million acres of land would need to be used for biodiesel cultivation in the US in order to produce biodiesel to replace all the petrodiesel used currently in that country. This is just 1% of the total land used today for farming and grazing together in the US (about 1 billion acres). Clearly, algae are a superior alternative as a feedstock for large-scale biodiesel production.

In practice however, biodiesel has not yet been produced on a wide scale from algae, though large scale algae cultivation and biodiesel production appear likely in the near future (4-5 years).

In order to produce biodiesel from algae on a large-scale, the following conditions need to be met, logically speaking:

Ability to sustainably produce high-oil-yielding algae strains on a large-scale Ability to extract the oil from the algae on a large scale Capability for large-scale conversion of algal oil into biodiesel

The first two aspects are specific to algae, while the third is a generic aspect for biodiesel production from all plant oils.

Based on the current research inputs, it appears that the real concern would be condition # 1: Capability to sustainably produce high-oil-yielding algae strains on a large-scale. While the other two conditions need to be addressed as well, those two are primarily engineering considerations over which we have more control than over condition #1. This, hence needs to be given more focus.

The capability to sustainably produce high-oil-yielding algae strains on a large-scale can again be thought to contain two distinct aspects: (1) Identifying the high-yielding Algal Strains and (2)

Identifying the most optimal methods to cultivate them. A good amount of research is taking place in each of these two aspects and it is hoped that there will be more good news soon. 

Algal Biodiesel Characteristics & Properties

Characteristics of algae biodiesel that differ from petro diesel:

Algae biodiesel has virtually no sulfur content. Biodiesel has superior lubricating properties, reducing fuel system wear, and increases

the life of fuel injection equipment. Algae biodiesel has more aggressive solvent properties than petro diesel and will dissolve

leftover varnish residue.  Fuel filters should be changed shortly after introducing biodiesel into systems formerly running on petrodiesel to avoid clogging.

Biodiesel has about 5-8 percent less energy density than petrodiesel, but with its higher combustion efficiency and better lubricity to partially compensate, its overall fuel efficiency decrease is only about 2 percent.

The cloud point, or temperature at which pure (B100) biodiesel starts to gel, is about   32 0F. A blend of B20 (20% biodiesel, 80% petrodiesel) generally does not gel in cold weather. Various additives will lower the gel point of B100.

Biodiesel's flash point (lowest temperature at which it can vaporize to form an ignitable mixture in air) is 2660F, significantly higher than petrodiesel's 1470F, or gasoline's 520F.

Biodiesel reduces particulate matter by about 47 percent as compared to petroleum diesel. Biodiesel has less dangerous particulate matter because it reduces the solid carbon fraction on the particulate matter while increasing the amount of oxygen.

Advantages of biodiesel produced from algae:

Higher yield and hence      – hopefully – lower cost The most significant      benefit is however in the yield      of algal oil, and hence

biodiesel.      According to some estimates, the yield (per Acre      say) of oil from algae is      over 200 times the yield      from the best-performing plant/vegetable oils. While soybean typically      produces less than 50 gallon of oil per acre and rapeseed generates less      than 130 gallon per acre, algae can yield up to 10,000 gallons per acre.

Algae       can grow practically in every place where there is enough sunshine The biodiesel      production from algae also has the beneficial by-product of reducing     

carbon and NOx Emissions from power plants, if the algae are grown using exhausts from the power plants.

Algae       produce a lot of polyunsaturates, which may present a stability problem      since higher levels of polyunsaturated fatty acids tend to decrease the      stability of biodiesel.      But polyunsaturates also have much lower melting points than     

monounsaturates or saturates, thus algal biodiesel should have much better      cold weather properties than many other bio-feedstock. Since one of the      disadvantages of biodiesel      is their relatively poor performance in cold temperatures, it appears that      algal biodiesel might score well on this point.

Methods of Hydrogen Production from Algae

There are three methods by which Hydrogen can be produced from algae.

Biochemical Processes - Under specific conditions, algae produce hydrogen, via biological and photobiological processes. Under these conditions, enzymes in the cell act as catalysts to split the water molecules. For more information see: Biophotolysis of water by microalgae and cyanobacteria

Gasification – Gasifying biomass gives syngas, a mixture of CO and H2. A number of methods are being researched to separate the H2 from syngas.During gasification, biomass is converted into a gaseous mixture comprising primarily of hydrogen and carbon monoxide, by applying heat under pressure in the presence of steam and a controlled amount of oxygen. The biomass is chemically broken apart by the gasifier's heat, steam, and oxygen, setting into motion chemical reactions that produce a synthesis gas, or "syngas" - a mixture of primarily hydrogen, carbon monoxide, and carbon dioxide. The carbon monoxide is then reacted with water to form carbon dioxide and more hydrogen

Through Steam Reformation of Methane – Fermentation of Algal Biomass produces methane. The traditional steam reformation (SMR) techniques can be used to derive hydrogen from methane.Steam reforming is the most common method of producing commercial bulk hydrogen as well as the hydrogen used in the industrial synthesis of ammonia. It is also the least expensive method. At high temperatures (700 – 1100 °C) and in the presence of a metal-based catalyst (nickel), steam reacts with methane to yield carbon monoxide and hydrogenCH4 + H2O → CO + 3 H2

Biophotolysis of Water by Microalgae

Microalgae are primitive microscopic plants living in aqueous environments. Cyanobacteria, formerly known as blue-green algae. Miroalgae and Cyanobacteria along with higher plants, are capable of oxygenic Photosynthesis according to the following reaction:

CO2 + H2O = 6 [CH2O] + O2

Photosynthesis consists of two processes: light energy conversion to biochemical energy by a photochemical reaction, and CO2 reduction to organic compounds such as sugar phosphates, through the use of this biochemical energy by Calvin-cycle enzymes. Under certain conditions,

however, instead of reducing CO2, a few groups of Microalgae and Cyanobacteria consume biochemical energy to produce molecular hydrogen. Hydrogenase and nitrogenase enzymes are both capable of hydrogen production.

Methane Production from Algae

Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler. Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. At about 891 kJ/mol, methane's combustion heat is lower than any other hydrocarbon; but a ratio with the molecular mass (16.0 g/mol) divided by the heat of combustion (891 kJ/mol) shows that methane, being the simplest hydrocarbon, produces more heat per mass unit than other complex hydrocarbons. In many cities, methane is piped into homes for domestic heating and cooking purposes. In this context it is usually known as natural gas, and is considered to have an energy content of 39 megajoules per cubic meter, or 1,000 BTU per standard cubic foot.

Methane in the form of compressed natural gas is used as a vehicle fuel, and is claimed to be more environmentally friendly than fossil fuels such as gasoline/petrol and diesel.

Theoretically, methane can be produced from any of the three constituents of algae – carbohydrates, proteins and fats.Closed algal bioreactors offer a promising alternative route for biomass feedstock production for bio-methane. Using these systems, micro-algae can be grown in large amounts (150-300 tons per ha per year) using closed Bioreactor systems (lower yields are obtained with open pond systems). This quantity of biomass can theoretically yield 200,000-400,000 m of methane per ha per year.

Methane Production by Anaerobic Digestion

This appears to be the most straight-forward method of producing methane from algae.A process for obtaining methane from algae, involves the following successive stages: - Pre-treatment of the algae, capable of producting a liquid suspension of fine solid particles, said treatment being moreover capable of partially depolymerizing the solid algae matter, - Running the suspension through a fluidized bed containing granules on which enzymes are immobilized which are capable of transforming the particles into sugar, said liquid containing acidific bacteria capable of transforming said sugars into volatile fatty acids, - Decantation of the suspension, so as to remove any solid particles that may remain, and to extract a decanted liquid, and

- Running the decanted liquid across a fixed bed containing methanogenic bacteria set onto a support so as to cause the liquid to release a gas mixture containing mainly methane

Methane Production by Pyrolysis / Gasification• One possibility for making methane from algae is the direct pyrolysis of microalgae. Wu et al. (1999) report the direct pyrolysis of marine nanoplankton as a source of methane and oils with Emiliania huxleyi, a widely distributed coccolithophorid species in world oceans with the authors suggesting this as one of the most promising candidates for the production of biofuel.• Methanation of syngas produced from gasification of Algal Biomass is another route to produce methane-rich syngas, sometimes also called synthetic natural gas.

Ethanol from Algae

Algae have a tendency to have a much different makeup than does most feedstocks used in ethanol, such as corn and sugar cane. Ethanol from algae is possible by converting the starch (the storage component) and Cellulose (the cell wall component). Put simply, lipids in algae oil can be made into biodiesel, while the carbohydrates can be converted to ethanol. Algae are the optimal source for second generation bioethanol due to the fact that they are high in carbohydrates/polysaccharides and thin cellulose walls

It’s not that it’s difficult to make ethanol from algae.

Veridium Corp is a subsidiary of GreenShift. (Mar 2006)

The real problem is that there are so many more valuable products to produce from it, such as carrageenan, agar, and dozens of valuable compounds. In comparison, alcohol is a low-priced product.

Algae Species for Ethanol Production

Some prominent strains of algae that have a high carbohydrate content and hence are promising candidates for ethanol production.

Sargassum Glacilaria Prymnesium parvum Euglena gracilis

Process behind Ethanol from Algae

Fermentation process to produce ethanol include the following stages:(a) Growing starch-accumulating, filament-forming, or colony-forming algae in an aqua culture environment;(b) Harvesting the grown algae to form a biomass;(c) Initiating decay of the biomass;(d) Contacting the decaying biomass with a yeast capable of fermenting it to form a fermentation solution; and,(e) Separating the resulting ethanol from the fermentation solution.Initiating decay means that the biomass is treated in such a way that the cellular structure of the biomass begins to decay (e.g., cell wall rupture) and release the carbohydrates. Initiating decay can be accomplished mechanically, non-mechanically. The yeasts used are typically brewers' yeasts (Saccharomyces cerevisiae and Saccharomyces uvarum). Besides yeast, genetically altered bacteria know to those of skill in the art to be useful for fermentation can also be used.

Ethanol from De-oiled Algae

Overall, the algal biomass comprises three main components – Carbohydrates, Proteins and Lipids. Once the lipids have been extracted the left-over cake is primarily composed of carbohydrates and proteins. Carbohydrates in the left-over algae can be converted into sugars. Depending on the strain, the sugar can either be simple or complex. Thus, the left-over be used as feedstock for ethanol.Algae cake that is left over after extraction of oil for biodiesel can be converted into ethanol through fermentation of the extract. This gives rise to the interesting possibility of producing both biodiesel and ethanol from algae! Add to this the fact that fermentation of algae extract to ethanol releases CO2, which can again be fed to grow more algae. Such a closed loop presents an attractive potential on which some initial trials are on-going.

De-Oiled Algae cake

 Algae meal could refer either to the Algal Biomass without extracting the oil, or to the deoiled oil cake. When oil is removed from the algal biomass, the resulting cake does not have lipid content, and is primarily rich in protein and carbohydrates.

 Algae cake is a source of nutrients for humans and animals, because the cake of many algal species has high protein content, sometimes as high as 50 to 60% of dry matter. Except for sulphur-containing amino acids (methionine and cystine), the essential amino acid content in many algal species is favourable for the nutrition of farm animals. Algae are also a rich source of carotene, vitamin C and K, and B-vitamins.

Overall, the algal biomass comprises three main components – Carbohydrates, Proteins and Lipids. Once the lipids have been extracted the left-over cake is primarily composed of carbohydrates and proteins. Depending on the growth medium and the nutrients, algae meal could contain some substances such as lead, arsenic, mercury, and heavy metals.

The exact composition of the algae meal depends on the algae species as well as the growth conditions. In addition, it also depends on the amount of oil that has been extracted.

Cultivation of Algae in Photobioreactor

Algae can be grown in a photobioreactor (PBR). A PBR is a bioreactor which incorporates some type of light source. Virtually any translucent container could be called a PBR; however the term is more commonly used to define a closed system, as opposed to an open tank or pond.

It allows more species to be grown, it allows the species that are being grown to stay dominant, and it extends the growing season, only slightly if unheated and if heated it can produce year round. Because PBR systems are closed, all essential nutrients must be introduced into the system to allow algae to grow and be cultivated. A PBR can be operated in "batch mode", but it is also possible to introduce a continuous stream of sterilized water containing nutrients, air, and carbon dioxide.

Algal culture systems can be illuminated by artificial light, Solar light or by both. Naturally illuminated Algal Culture systems with large illumination surface areas include flat-plate, horizontal/serpentine tubular airlift, and inclined tubular photobioreactors .Generally, laboratory-scale photobioreactors are artificially illuminated (either internally or externally) using fluorescent lamps or other light distributors.

Working of a photobioreactor:

Flow description:

1. From the feeding vessel, the flow progresses to the diaphragm pump which moderates the flow of the algae into the actual tube. Built into the pump is the CO2 inlet valve.

2. The photo-bioreactor itself is used to promote biological growth by controlling environmental parameters including light. The tubes are acrylic and are designed to have light and dark intervals to enhance the growth rate.

3. The photobioreactor has a built-in cleaning system that will be internally clean the tubes without stopping the production.

4. After the algae have completed the flow through the photobioreactor, it passes back to the feeding vessel. As it progresses through the hoses, the oxygen sensors determine how much oxygen has built up in the plant and it is released in the feeding vessel itself. It is also at this stage that the optical Cell Density sensor determines the harvesting rate.

5. When the algae are ready for harvesting, the algae passes through the connected filtering system. This filter collects the algae that are ready for processing, where the remaining algae passes back to the feeding vessel.

6. And the flow continues.

Advantages of using a photobioreactor:

High Biomass Productivity and cell density Less contamination, water use, & CO2 losses Better light utilization & mixing Controlled culture conditions

Disadvantages of using a photobioreactor:

High capital cost associated with construction costs, circulation pumps, and nutrient-loading systems

Absence of evaporative cooling, which can lead to very high temperatures Accumulation of high concentration of photosynthetically generated O2 leading to

photooxidative damage Biofouling of interior surfaces and difficulty of cleaning them Cell damage by shear stress Deterioration of materials

Requirements to develop a high-performance Photobioreactor for algal cultivation:

In order to attain high productivity, the volume of the non-illuminated parts of the reactor should be minimized.

In order to ensure a high efficiency of light use by the culture, the design must provide for the uniform illumination of the culture surface and the fast mass transfer of CO2 and O2.

To prevent rapid fouling of light-transmitting surfaces of reactors, photobioreactors must be frequently shut down for their mechanical cleaning and sterilization

High rates of mass transfer must be attained by means that neither damage cultured cells nor suppress their growth.

For the industrial-scale production of biomass, the energy consumption required for mass transfer and the arrangement of the light-receiving surface of the algal suspension must be reduced to its minimum possible.

Cultivation of Algae for CO2 Capture Algae live on a high concentration of carbon dioxide and nitrogen dioxide.  These pollutants are

released by automobiles, cement plants, breweries, fertilizer plants, steel plants. These pollutants can serve as nutrients for the algae.

Using algae for reducing the CO2 concentration in the atmosphere is known as algae-based

Carbon Capture technology. The algae production facilities can thus be fed with the exhaust gases from these plants to significantly increase the algal productivity and clean up the air.  An additional benefit from this technology is that the oil found in algae can be processed into a biodiesel. Remaining components of the algae can be used to make other products, including Ethanol and livestock feed.

This technology offers a safe and sustainable solution to the problems associated with global warming.

Cultivation of Algae in Sewage & Wastewater Treatment Plant

The cultivation of Algae is expected to bring double benefit to the environment in the sense that Algae can be used to extract nutrients from waste water, which it converts to fats for bio diesel production and Algae extracts pollution from the atmosphere.

Aside from the fact that expensive reactor systems are not required (presumably some sort of effective harvesting system would however be needed), unlike other algal-biofuel technologies this approach relies on ‘wild algae’ - ie. algae that naturally colonize sewage ponds already.There is even a company in New Zealand (AquaFlow) that has a small shed next to the tertiary holding ponds at a sewage treatment plant that is producing just enough Biodiesel to provide 5 percent of the fuel for a small SUV

Algae Harvesting

Gathering algae consists of separating algae from the growing medium, drying, and processing it to obtain the desired product. Separating algae from its medium is known as harvesting. Harvesting methods depends primarily on the type of algae. The high water content of algae must be removed to enable harvesting. The most common harvesting processes are flocculation, microscreening and centrifugation. These must be energy-efficient and relatively inexpensive so selecting easy-to harvest strains is important.

Macroalgae harvesting employs manpower whereas, microalgae can be harvested using microscreens, centrifugation, flocculation or by froth flotation.

Algae Oil Extraction

Oil extraction from algae is a hotly debated topic currently because this process is one of the more costly processes which can determine the sustainability of algae-based biodiesel.

In terms of the concept, the idea is quite simple: Harvest the algae from its growth medium (using an appropriate separation process), and extract the oil out of it. Extraction can be broadly categorized into two methods:

Mechanical methods

The mechanical methods are further classified into:

Expression/Expeller press Ultrasonic-assisted extraction

Chemical methods

The chemical methods are further classified into:

Hexane Solvent Method Soxhlet extraction Supercritical fluid Extraction 

Each of these methods has drawbacks: 

The mechanical press generally requires drying the algae, which is energy intensive The use of chemical solvents present safety and health issues Supercritical extraction requires high pressure equipment that is both expensive and

energy intensive. 

Many manufacturers of algae oil use a combination of mechanical pressing and chemical solvents in extracting oil.

Apart from these, there are some other methods which are not well-known. This includes the following:

Enzymatic extraction - Enzymatic extraction uses enzymes to degrade the cell walls with water acting as the solvent, this makes fractionation of the oil much easier. The costs of this extraction process are estimated to be much greater than hexane extraction.

Osmotic shock - Osmotic Shock is a sudden reduction in osmotic pressure, this can cause cells in a solution to rupture. Osmotic shock is sometimes used to release cellular components, such as oil.

CHALLENGES IN OIL EXTRACTION FROM ALGAE:

Microscopic algae suspended in water are virtually indestructibleo Cell wall has a high elasticity moduluso Even when free water has been removed, wet biomass retains sufficient interstitial

water to act as lubricant Rupture of cell wall through mechanical friction and steam explosion is only possible

when dry

BREAKTHROUGHS IN OIL EXTRACTION FROM ALGAE:

a.Single-Step Extraction:

The OriginOil’s algae Single-Step oil extraction process is simpler and more efficient than current systems, without requiring chemicals or significant capital expenditure for heavy machinery.

The Single Step Process harvests, concentrates and extracts oil from algae, and separates oil, water and biomass in one step. The process does not use chemicals or heavy machinery and no initial dewatering is required, and separates the oil, water and biomass in less than an hour. The company’s Quantum Fracturing technology combines with electromagnetic pulses and pH modification to break down cell walls and release oil from the algae cells.

OriginOil’s Single-Step Algal Oil Extraction

b. Continuous algal oil extraction system:

Cavitation Technologies Inc. (CTI) has developed a technology that is able to extract oil from algae on a continuous basis utilizing cavitation based extraction. CTI’s Nano reactor is used to create cavitation bubbles in a solvent material, when these bubbles collapse near the cell walls it creates shock waves and liquid jets that cause those cells walls to break and release their contents into the solvent. The company plans to license the technology to algal fuel developers.

c. Extraction using nanotechnology:

Catilin and Iowa State University - Center for Catalysis (ISU-CCAT), members of the National Alliance for Advanced Biofuels and Bioproducts (NAABB), will build on their pioneering algal oil extraction technology using mesoporous nanoparticles to selectively extract and sequester targeted fuel-relevant and high value compounds within the algal lipid mixture. The balance of the algal oil, which contains free fatty acids (FFA) and triglycerides, will be converted to Biodiesel using Catilin's commercially available T300 catalyst. This technology is efficient and solid catalyst provides a cost effective conversion route.

Algae Product Basket - Biodiesel, Ethanol, Methane & Hydrogen

Biodiesel is the most commonly discussed energy output from algae, but it is not the only one. A serious study of the energy domain and of algae points to a wide basket of energy outputs that can be theoretically derived from algae – all the way from gasoline to hydrogen to LPG. The following is the list of fuels that can be obtained from algae.

   *Biodiesel   *Ethanol   *Hydrogen   *Methane   *Biomass – where algae biomass is directly used for combustion    * Other hydrocarbon fuel variants, such as JP-8 fuel, gasoline, biobutanol etc.

 In order to derive the various energy products from algae, the Algal Biomass needs to be put through different processes.

Final Product ProcessesBiodiesel Oil extraction and TransesterificationEthanol Fermentation

MethaneAnaerobic digestion of biomass; Methanation of syngas produced from biomass

HydrogenTriggering biochemical processes in algae; Gasification / pyrolysis of biomass and processing of resulting syngas.

Heat & Electricity Direct combustion of algal biomass; Gasification of biomassOther Hydrocarbon Fuels

Gasification/pyrolysis of biomass and processing of resulting syngas

Biodiesel from Algae

Biodiesel refers to any diesel-equivalent biofuel made from renewable biological materials such as vegetable oils or animal fats. While there are numerous interpretations being applied to the term biodiesel, strictly speaking, the term biodiesel usually refers to an ester, or oxygenate, made from the oil and alcohol.

Bio-diesel can be used in diesel engines either as a standalone or blended with petro diesel. Much of the world uses a system known as the "B" factor to state the amount of biodiesel in any fuel mix. For example, fuel containing 20 % biodiesel is labeled B20. Pure biodiesel is referred to as B100.

One of the key reasons why algae are considered as feedstock for oil is their yields. DOE (Department of Energy, Gov of USA) is reported as saying that algae yield 30 times more energy per acre than land crops such as soybeans, and some estimate even higher yields up to 15000 gallons per acre.

Producing biodiesel from algae provides the highest net energy because converting oil into biodiesel is much less energy-intensive than methods for conversion to other fuels (such as Ethanol methane etc). This characteristic has made Biodiesel the favourite end-product from algae. Producing biodiesel from algae requires selecting high-oil content strains, and devising cost effective methods of harvesting, oil extraction and conversion of oil to biodiesel.

Detailed Process of Biodiesel from Algae