Question

write a report about ( Biological CO2 mitigation by microalgae ) thermofluid Mechanics . Note : only 3 pages .

Answer 1

CO, Mitigation Potentials of Microalgae: Its Expansion to a New Dimension for Closing the Loop of Carbon Between Source and Acquisition Through Food Chain of Phytophagous Fish in Open Ponds BB Jana" International Centre for Ecological Engineering, Centre for Human Resource Development (KSI), University of Kalyani, India Submission: September 17, 2018; Published: January 03, 2019 *Corresponding author: B B Jana, International Centre for Ecological Engineering, University of Kalyani, Kalyani-741235, West Bengal, India Abstract The burning issue of global warming and climate change has become a major worldwide concern of the day. Though numerous efforts are being made for mitigation of carbon, use of microalgae for capturing carbon in water bodies appear to be more attractive and promising because of their much higher bicarbonate driven carbon capture efficiency in water than atmospheric co, capture performance by terrestrial plants. Microalgae have been effectively used for biofuel and biochar production through biotechnological approach, the less explored area is its use in closing the loop of carbon cycle by trapping atmospheric carbon mediated through CO - CO,- HCO, system mechanism and production of nutrient regulated selective algae used for food for herbivorous fishes in open ponds. This is a win-win strategy towards carbon mitigation and low carbon foot print fish production in water bodies. Keywords: Chlorella growth, aeration, C-sequestration, compressed CO,, open ponds Introduction Unbalanced emissions of atmospheric Co, causing global warming and climate change pose major threat to sustainability Three major strategies that can reduce the carbon pool in the atmosphere below threshold level include: a. reductions in CO emissions in the global atmosphere. b. carbon capture for long-term storage using oceanic, geological, and chemical processes. c. exploring alternative energy source for carbon-based fuel. Though oceanic, geological and chemical transformation methods are the major sources of carbon capture, biological sequestration especially using smart agriculture and aquaculture appear to be more attractive and promising because of ease, cost effective, and negative environmental impacts. Despite microalgae have been extensively researched for biofuel or biochar production through biotechnological interventions [1, 2, 3]; the less explored area is its use in closing the loop of carbon between capture and smart carbon resilient aquaculture of herbivorous fishes in open ponds. This is a win-win strategy towards carbon mitigation and production of low carbon foot print fish especially in tropical countries. The purpose of the study is to overview the role of microalgae in global warming mitigation and to focus on closing the loop in carbon cycle by exploiting the trapped carbon through food chain of low carbon foot print fish in open ponds. Microalgal photosynthesis Microalgae have chlorophyll a though their several modifica- tions have occurred through evolution in higher plants. Chloro- phylls are made up of lipid-soluble hydrocarbon tail (C,H,,-), a hydrophilic head and a magnesium ion at the center. Photosynthe- sis is a process where conversion of photon energy into chemical energy occurs to form glucose and water and oxygen is released (Figure 1) as byproduct. Though visible spectrum is the source of energy, the maximum contributions are from the violet-blue, red- dish orange- red wavelengths of the spectrum. The photoactiva- tion is the first stage of photosynthesis when absorption of energy from a photon takes place in raising a molecule from its ground state or chromophore. As a result, water molecules are split off and transfer of energy to ATP and reduced NADP (nicotinamide adenine dinucleotide phosphate) are produced. The chloroplast contained in the chlorophyll of microalgae, similar to other plants, is the site of photosynthetic reactions carried out in two separate steps of reactions - the biophysical and biochemical (Figure 1). The biophysical reactions take place in the thylakoid discs of the chloroplasts and water is oxidized, Adv Biotech & Micro 12(1): AIBM.MS.ID 555827 (2019) 003

Advances in Biotechnology & Microbiology and oxygen is produced (Figure 2). The energy produced in the form of ATP and NADPH is used to fix or assimilate Co, in the dark reactions. The biochemical reaction occurs in the chloroplast stroma resulting in the formation of primarily sugar molecules with some other organic molecules required for cell function and metabolism of microalgae. Chloroplast PEADP fi melal Rubis fecules SP BRA SATP ADP NAD Calvin Cycle NAME les NADH NADP- Imlule GP TO Ch mchane Figure 1: An overview of the photosynthetic process and 3-stages of Calvin cycle in microalgae CH10 ATP CONADP Hase ATT 11 PSII Cyt PSI Thylakoid membrane 10 HANG 211 211.0 Figure 2: Overview of photosynthesis and photolysis of microalgae (ATP adenosine triphosphate, CH O formaldehyde, NADPH nicotin- amide adenine dinucleotide phosphate, Hase hydrogenase, PSI photosystem I. PSIl photosystem II, Fá ferrodoxin, PC platocyanin, PQ plastoquinone) Advantage of carbon sequestration by microalgae in ponds is about 0.21% of the annual global emissions. However, wetlands under unmanaged anaerobic conditions, wetlands can also emit The role of wetlands with a hot spot of green biodiversity has greenhouse gases such as methane, nitrous oxide and hydrogen generally been underestimated despite their immense carbon sulphide though this is limited in saline conditions or swampy capture and storage capacity potentials [4, 5, 6, 7). Wetlands areas. Further, the clearing or drainage of wetlands or aquaculture contain about 35 per cent of global terrestrial carbon though ponds can lead to large losses of stored organic carbon to they comprise only 6.9% of the Earth's surface. The carbon flux atmospheric carbon dioxide. Notwithstanding the manifold in water bodies depends on surface area, water concentrations positive impacts of wetlands overweighed towards beneficial and gas transfer velocity. However, the functional roles of pond environmental impacts and led to argue that wetland should not be destroyed or restored because of GHG emissions under limited metabolism finally determine the nature of pond soil to act as a sink or source of carbon. The net sinks for carbon in different conditions (13) wetlands have been estimated to be at rates up to 3 g Cm-2d-118, A major advantage of microalgae in aquatic environment is 9, 10). Sediments of aquaculture ponds are again very important the 100% harvest of the production, and the carbon fixing rates in the carbon sequestration. Approx. 16.6 million tons of carbon of microalgae are much higher than in terrestrial plants. It is is annually buried in aquaculture ponds of the world (11) and known that 1.6 and 2 grams of captured CO, is used for every maximum sequestration occurs in Asia and particularly in gram algal biomass [14). As CO, is present in atmosphere in China (12). In other words, carbon sequestration by aquaculture concentration lower than nitrogen (N) and oxygen (0), this has

Advances in Biotechnology & Microbiology created a thermodynamic barrier in CO, capture. Nevertheless, One of the excellent abilities of aquatic cyanobacteria and high coefficient solubility of Co, makes it far more soluble than eukaryotic algae is to use all forms of dissolved inorganic carbon atmospheric oxygen and nitrogen (15). Carbon dioxide reacts with (free CO, - C0,- HCO) at different pH conditions in aquatic water; the carbon atom of Co, is electron poor with an oxidation environment. The CO, CO, HCO3 system acts as a buffer as state of IV. The electron rich oxygen of water donates an electron well as a source of carbon for the photosynthetic microalgae at pair to the carbon. After proton transfer from water to oxygen of different pH conditions (16). Among the three-chemical species the Co, unit, carbonic acid is formed and then into bicarbonate and of carbon in water, bicarbonate (HCO ) is most dominant (>50%) hydrogen, resulting in lowering of the pH - a favorable condition at pH between 6.4 and 10.3, whereas carbonic acid (H.CO) and when Co gets dissolved in water, carbonate (CO) are dominant at pH < 6.4 and > 8.3, respectively [17, 18). Carbon capture potentials of microalgae Coro 600 500 400 Number of chlorella cell (ml") 300 200 100 0 0 24 48 72 144 166 1A 196 211 240 241 272 Periods (h) Figure 3: Growth of Chlorella sp. in different culture conditions. Algae media - Normal (Control), Algae media - Aerated (T1). Algae media - Liquid CO, introduction (T2). The microalgae are able to capture as high as 90% of carbon growth rates than the other three strains tested. The two algae dioxide or bicarbonate in open ponds though the ability varies again had very similar light response curves. Scenedesmus was among species. Scenedesmus was better able to tolerate very high completely inhibited by 100% CO, A microalgal consortium CO, concentrations than Chlorella though both algae had about consisting of Chlorella sp., Scenedesmus sp., Sphaerocystis sp. and the same growth rate when the CO2 concentration remained Spirulina sp. procured from wastewater ponds revealed quite in the range of 10 - 30%. Strains of microalgae that are able high CO, sequestration (53- 100%; 150-291 mg/g) [21]. While to tolerate about 20% CO, (Scenedesmus, Chlorococum and examining the growth of Chlorella under controlled laboratory Ankistrodesmus) formed several separate branches suggesting culture medium (Hi Media) using aerated exogenously introduced that certain groups or genotypes of algae tend to perform better compressed co2 and control revealed no marked growth under high CO level compared with other algal groups [19, 20). difference among the conditions, showing the peak between 166 - demonstrated that Scenedesmus and Chlorella had much higher 218 hours of culture (Figure 3). pH 4 PHS pH --PH9 pH 6 - pH 10 pH 7 pH 11 O.D value 0.9 08 0.7 0.6 0.5 0.4 03 0.2 0.1 0 O HR 24 HR 48 HR 72 HR 96 HR 120 HR 144 HR Time Figure 4: Growth of Chlorella sp. at different pH conditions