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How you pronounce the word, "algae" can be just as mysterious as what it means. As an environmental scientist and National Geographic Explorer, Branwen Williams demystifies algae and the different forms it can take. When we want a greater supply, all we need to do is grow more. In fact, some species of algae can double their number in 24 hours.
Because algae use carbon dioxide through photosynthesis, algae biofuel is carbon neutral. The CO2 produced by burning the fuel is the same amount of CO2 that the algae took to grow and produce the fuel. This means that the net CO2 emission is zero, the same as if the algae had never been grown. Compared to other sources of biofuels, algae can produce much more oil per acre— 10 to times more.
And unlike some other biofuel sources like corn or soybean, algae is not a primary food source for humans or livestock. Algae can be grown in numerous locations, including wastewater or water around power plants or factories. It can grow in any climate, as long as there is enough sunlight, meaning that it can be grown in areas that are inefficient for other agriculture. Algae biofuel is also virtually harmless to the environment. We can use hydrocarbons from algae biomass in the same way we use them for petroleum-based items to make things like fertilizers, soap products, industrial cleaners, or feedstocks.
Algae can not only produce biofuel but other useful products as well. Algae biofuel can be refined in a similar way to petroleum products, which means it could become a direct replacement for fuels we already use. The fuel can be used in cars, machines, other types of vehicles, jets, and even as oil for cooking. While interest and research into algae biofuel have been growing, information is still limited.
Algae require a significant water source available to maximize growth. Temperature levels for the best growth cause water to evaporate, so algae biofuel uses much more water than other resources. This means that agricultural water resources may have to be diverted and used. Table 3 shows oil contents of different microalgal species [ 30 ]. Microalgae can grow in wastewater, thus giving it the ability to address treatment, utilization and disposal concerns [ 9 ].
Also, it can be grown in arid and semi-arid regions with poor soil quality, with a per hectare yield estimated to be many times greater than that of even tropical oil seeds [ 9 ]. Microalgae can be considered as a sustainable energy source of next generation biofuels [ 31 ]. Microalgae are able to create oil along the year. Microalgae produce oil is more compared to conventional crops.
Microalgae yield 15— times greater oil for biodiesel production than traditional crops. Biodiesel yield from algal lipid is distinguished with a high biodegradable and non-toxic. Microalgae can cultivate in high amounts arrived to 50 times greater than that of switchgrass, which is the more growing terrestrial crop.
Microalgae can complete the whole growth cycle in limited days by way of photosynthesis process that alters sun energy into chemical energy. They grow in fresh water, seawater, wastewater or non-arable lands [ 5 ]. The cultivation of microalgae needs less water than other energy oil crops. Table 4 shows the comparison between the different sources of biodiesel [ 32 ].
Production of biodiesel from microalgae can fix CO 2. Roughly 1 kg of algae biodiesel fixes 1. Microalgae cultivation has a higher CO 2 mitigation rate between Microalgae cultivation can use phosphorus and nitrogen as nutrients from wastewater resources. Therefore, microalgae can provide the additional advantage for wastewater bioremediation. Furthermore, microalgal biodiesel can decrease the liberation of NO x. Microalgae yield significant by-products for instance H 2 , ethanol, biopolymers, carbohydrates, proteins, beautifying products, animal feed, enricher, biomass remains, etc.
Improvement of microalgae does not need stimulant for growth. The warming value of microalgal biodiesel is greater than that of the other terrestrial plants.
Algal biomass is a renewable resource that has the potential to supply a limited portion of international energy needs [ 36 ]. Preference toward microalgae is due largely to its less complex structure, fast growth rate and high-oil content for some species This characteristics of the strain should be taken into consideration. There are greater than , types of algae, with varying ratios of three main types of molecule: protein, oils and carbohydrates.
Types of algae great in carbohydrates in addition to oils create starches that can be liberated then fermented into ethanol; the residual proteins can be converted into animal grains [ 1 ]. Research into algae for the mass-production of oil is mainly focused on microalgae organisms capable of photosynthesis that are less than 0.
In the end of eighteenth century, Robert Koch was one of the first scientists focused on the isolation of microorganisms in pure culture, followed by Sergei Winogradsky who initiate the field of microbiology and he was responsible for the first isolation of microorganism.
There are four main techniques for obtaining unialgal isolates: spraying, streaking, serial dilution and single-cell isolations [ 37 ]. Spraying and streaking are useful for single-celled, colonial or filamentous algae that will grow on an agar surface; cultures of some flagellates may also be founded by these methods.
A lot of flagellates and in addition to other forms of algae, must be separated by single-organism isolations or serial-dilution procedures. Spraying procedure, a stream of air is utilized to diffuse algal cells from a mixture onto the surface of a petri plate having solidified medium with agar for growth. Hold a pipette in both hands; the tip end is caught with a forceps so that the glass near the tip is within the flame of a Bunsen burner gas flame.
The pipette is held in the flame only until the glass becomes marginally soft. This is determined by testing for flexibility by moving the tip with the forceps. Then the pipette is removed from the flame and pulled out straight or at an angle so that there is a bend.
You can differ the diameter of the fine pulled tip by altering the speed of pulling. You would need a fine diameter tip if you are trying to separate very small algae, but a bigger diameter tip is necessary for large cells.
Addition of antibiotics to the growth medium is necessary to prevent growth of cyanobacteria and other bacteria, while addition of germanium dioxide will inhibit diatoms growth. Treatment of culture, isolated algae, by an extensive washing procedure via one or more antibiotics is called axenic culture. Resistant stages such as zygotes or akinetes can be treated with bleach to kill epiphytes, and then planted on agar for germination.
Two basic alternatives for microalgae cultivation exist and their relative merits are the basis of ongoing debate. Microalgae cultivation using sunlight energy can be carried out in open ponds, covered ponds or closed photobioreactors, based on tubular, flat plate or other designs [ 38 ]. Algae houses are utilizing numerous variance methods to grow the algae, involving covered ponds, open ponds, bioreactors and raceways.
Algae grow normally in brackish, fresh or salt water centered on the algae species. An algal biofuels house must assess the cost and accessibility of water at the site of the production capacity. Water evaporation is the main problem, may be depending on the climate or whether of the system that used for growth of the algae open or closed.
Table 5 presents a short comparison of open pond systems and closed photobioreactors. Each system has benefits and drawbacks with respect to optimal growth conditions. Advantages and disadvantages of open pond and closed systems which are used for algal growth.
Figure 6 shows fixation of carbone dioxide in photobioreactors, utilizing microalgae to convert carbon dioxide and solar energy into algal biomass through photosynthesis process. The microalgae transferred to isolated photobioreactor for hydrogen creation, where the algae will transform solar energy into hydrogen gas using a biophotolytic procedure under sulfur deficiency. After the hydrogen yields stage, the algal biomass will be gathered and used for various purposes: the algae can be utilized immediately as a food for human or as animal feed or in aquaculture.
After nutrient control, algal biomass can hold big quantities of important biomolecules, which will be removed for industrial trade. However, these substances generally contain few percent of the biomass, leaving the common of the fixed carbone dioxide in the residual biomass.
The remaining algal biomass from different method steps can be utilized either as a fertilizer for agriculture in which case the fixed carbon will be retained for some years, or for storing of the fixed carbone dioxide by industrial uses like manufacture of plastics. Remaining biomass can also be utilized as an energy transporter by removal of biodiesel through the direct conversion of the biomass to other energy transporters by biological or thermochemical procedures [ 39 ].
Fixation of carbone dioxide in photobioreactors, utilizing microalgae to convert carbon dioxide and solar energy into algal biomass through photosynthesis process. Photobioreactors, the closed systems are much more expensive than ponds.
PBR can have different sizes and shapes: plastic bags, flat panels, tubes, fermenter like and others, as shown in Figure 7. Vertical tubes are the most popular system due to their relatively easy maintenance, high surface to volume ratio and low cost [ 40 ].
Between the advantages of utilizing photobioreactors are resistance to infection with uninhabited algae types and the possibility of simply controlling different factors, including temperature, light intensity and pH. The PBR can be located outdoors or indoors using artificial light or sunlight or a mixture of both.
A recent study showed that different wavelengths may have a significant influence on biomass and lipid productivity, as well as on the lipid profile [ 41 ]. Different shapes of closed system. Open ponds can be considered a cheap and easy to build, as extended as the area is relatively flat. Cultivation can be prepared immediately above the soil and some simple surface covering for reducing water loss due to seepage, and the other enhancements can be prepared to increase solar energy capture, and reduce the contamination process.
The most common types are raceway Figure 8 , circular, inclined and unmixed. Open-pond systems for the most part have been given up for the cultivation of algae with high-oil content [ 43 ]. Open systems using a monoculture are vulnerable to viral infection. However, such open ponds also suffer from various limitations, including more rapid than closed systems biological invasions by other algae, algae grazers, fungi, amoeba, etc.
It became a main problem, limiting its latter problem is offered. Wastewaters and marine waters can be used as environment and considered a good match for this system due to the water sustainability issues that would prevent large open-pond cultivation from using potable water and the cost of this operation is relatively low.
Therefore, this system is able to generate the biomass with a good price [ 44 ]. In general, open ponds constitute the cheapest method of producing algae in large quantities [ 45 ].
Open system raceway pond. Nutrients such as phosphorus P , potassium K and nitrogen N are vital for microalgae growth and are necessary quantities of fertilizer. Iron and silica, in addition to many trace elements, which considered essential marine nutrients, the lack of one can limit the growth of microorganism.
A suitable nutrient source for algae is from the sewage wastewater treatment, agricultural, flood plain run-off, all presently major pollutants. However, this wastewater cannot feed algae immediately, but the first process through anaerobic digestion by bacteria.
If wastewater is not processed before it reaches the algae, it will possibly kill much of the desired algae strain. Anaerobic digestion of wastewater produces a mixture of methane, carbon dioxide and organic fertilizer. Since the organic fertilizer that comes out of a digester is liquid, and approximately suitable for algae growth, it must first be cleaned and sterilized [ 1 ].
One method to increase productivity is to increase the concentration of carbon dioxide [ 44 , 46 ]. Indeed, the enzyme responsible for CO 2 fixation ribulose-1,5-bisphosphate carboxylase oxygenase , has a little affinity for CO 2 and also functions as an oxidase of 1,5-bisphosphate, act with oxygen. So, oxygen is a competitive inhibitor with CO 2 and subsequently the atmospheric concentration of CO 2 is amount lower than that of oxygen, which can has a major effect.
Assessment of this problem has been achieved by the improvement of carbon concentration mechanisms, where the cell locally induces the CO 2 concentration around the Rubisco enzyme to confirm its function in CO 2 fixation [ 47 ]. So this mechanism is common between the algae and demonstrates the benefits of increasing of the CO 2 concentration in mass cultures. Actually, dispersing CO 2 into the culture medium is known to raise its cellular density and two different methods are often reported, the use of CO 2 to adjust pH and CO 2 enrichment as a way to moderate flue gas [ 48 ].
Of course any feedstock used in large-scale production will play an important role on the price and CO 2 is not an exception.
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