BIOHYDROGEN PRODUCTION and UTILISATION- Progress Made So Far :BIOHYDROGEN PRODUCTION and UTILISATION- Progress Made So Far RAKESH KUMAR MAJHI NISER BHUBANESHWAR rakesh@niser.ac.in


THIS ARTICLE IS BASED ON MAINLY: :THIS ARTICLE IS BASED ON MAINLY: Biohydrogen production: prospects and limitations to practical application David B. Levin, Lawrence Pitt, Murray Love University of Victoria International Journal of Hydrogen Energy 29 (2004) 173 – 185


Slide 3:Biohydrogen technologies provide a wide range of approaches to generate hydrogen. It includes : Direct Biophotolysis Indirect Biophotolysis Photo-Fermentations Dark-Fermentation Water-Gas Shift Reaction While biohydrogen systems can produce Hydrogen, No commercial systems are yet available


DIRECT BIOPHOTOLYSIS :DIRECT BIOPHOTOLYSIS Photosynthetic production of hydrogen from water is a biological process that can convert sunlight into useful, stored chemical energy by the following general reaction: 2 H2O?2H2 +O2 Green algae, under anaerobic conditions, can either use H2 as an electron donor in the CO2- Oxidation process or evolve H2. The hydrogenase combines protons (H+) in the medium with electrons(donated by reduced ferredoxin) to form and release H2.


Slide 6:Hydrogenase is highly sensitive to Oxygen Therefore Photosynthetic production of Hydrogen & Oxygen must be temporarily /spatially separated. This can be achieved by incubating the microalgae in medium that doesnot contain Sulfur-containing nutrients. When culture of the green alga Chlamydomonas reinhardtii are deprived of inorganic S, the rates of O2 synthesis and CO2 Oxiation decline signifcantly within 24 h (in thelight).


Slide 7:Reason for this loss of activity is due to the need for frequent replacement of the H2O-oxidizing protein D1 in the PSII reaction centre [11]. Depletion of sulfur blocks the synthesis of the D1 polypeptide chain (32 kDa), which contains many sulfur containing amino acids, such as cysteine and methionine. While photosynthetic capability declines greatly, respiration continues, and after approximately 22 h of sulfur deprivation, C. reinhardtii cultures maintained in the light become anaerobic, and begin to synthesize H2 The rate of H2 production by C. reinhardtii reported by Kosourov et al. [12] was 7 .95 mmol H2/l of culture after 100 h, which corresponds to approximately 0.07 mmole H2=(l × h).


INDIRECT BIOPHOTOLYSIS :INDIRECT BIOPHOTOLYSIS Cyanobacteria can also synthesize & evolve H2 through photosynthesis via the fol. processes: 12 H2O + 6 CO2?C6H12O6 + 6 O2; (15)? C6H12O6 + 12 H2O?12 H2 + 6 CO2 Cyanobacteria contain photosynthetic piments, such as chl a, carotenoids, and phycobiliproteins and can perform oxygenic photosynthesis. Within the filamentous cyanobacteria, vegetative cells may develop into structurally modifed and functionally specialized cells, such as the akinetes (resting cells) or heterocysts (specialized cellsthat perform nitrogen-fixation; [15]).


Slide 9:These include nitrogenases which catalyze the production of H2 as a by-product of nitrogen reduction to ammonia, uptake hydrogenases which catalyze the oxidation of H2 synthesized by the nitrogenase, Bi-directional hydrogenases which have the ability to both oxidize and synthesize H2 [15]. Rates of H2 production by non-nitrogen-fixing cyanobacteria range from 0:02 mol H2/mg chl a/h (Synechococcus PCC 6307) to 0:40 mol H2/mg chl a/h (Aphanocapsa montana) [18].


Slide 10:Heterocystous cyanobacteria produce H2 in the range from : 0:17 mol H2/mg chl a/h (Nostoc linckia IAM M-14) to 4:2 mol H2/mg chl a/h (Anabaena variablilis IAM M-58) [19]. Mutant strains of A. variabilis have demonstrated significantly higher rates of H2 production compared with wild-type strains. A. variabilis PK84, for example, produced H2 at a rate of 6:91 nmol/g of protein/h (in 350 ml cultures). When A. variablis PK84 was cultured under conditions of nitrogen starvation, the rate of H2 synthesis was 12:6 mol/g of protein/h (in 350 ml cultures).[20].


PHOTO FERMENTATION :PHOTO FERMENTATION Purple non-sulfur bacteria evolve molecular H2 catalyzed by nitrogenase under nitrogen-deficient conditions using light energy and reduced compounds(organic acids). C6H12O6 + 12 H2O ? 12 H2 + 6 CO2 In general, rates of hydrogen production by photoheterotrophic bacteria are higher when the cells are immobilized in or on a solid matrix, than when the cell are free-living. Continuous cultures of Rhodopseudomonas capsulata and Rhodobacter spheroides were reported toproduce H2 at rates that range from 40 to 50 ml H2/l of culture/h [21,32,33], 80 ml to 100 ml H2/l of culture/h[25].


Slide 12:Continuous cultures of Rhodospirillum rubrum were reported to produce H2 at a rate of 180 ml H2/l of culture/h [28]. Rates of H2 production by Rb. SpheroidesGL1 immobilized on activated glass were 3.6–4:0 ml H2/ml/h [31,34]. If the system of culturing Rb. spheroides on porous glass could be scaled-up without compromising the rate of H2 synthesis, this would result in rates of 3.6–4:0 l H2/l of immobilized culture/h, which would correspond to 0:145 mmol H2/(l × h) to 0:161 mmol H2/(l × h).


DARK FERMENTATION :DARK FERMENTATION Hydrogen can be produced by anaerobic bacteria, grown in the dark on carbohydrate-rich substrates. Fermentation reactions can be operated at mesophilic (25–40?C), thermophilic (40–65?C), extreme thermophilic (65–80?C), or hyperthermophilic (>80?C) temperatures. While direct and indirect photolysis systems produce pure H2, dark-fermentation processes produce a mixed biogas containing primarily H2 and carbon dioxide (CO2).


Slide 14:Bacteria known to produce hydrogen include species of Enterobacter, Bacillus, and Clostridium. Carbohydrates are the preferred substrate for hydrogen-producing fermentations. Glucose, isomers of hexoses, or polymers in the form of starch or cellulose, yield different amounts of H2 per mole of glucose, depending on the fermentation pathway & end-product(s). Clostridium pasteurianum, C. butyricum, and C. beijerinkii are high H2 producers, while C. propionicum is a poor H2 producer [44]


Slide 15:To maximize the yield of H2, the metabolism of the bacterium must be directed : Away from alcohols (ethanol, butanol) and reduced acids(lactate)? Towards volatile fatty acids(VFA). C. pasteurianum is a classic H2 and VFA producer, but its metabolism can be directed away from H2 production and towards solvent production by high glucose concentrations (12.5% w/v), by CO (which inhibits Fe-hydrogenase), & by limiting Fe concentrations[ 45].


Slide 16:The best rate obtained with a pure culture of Clostridium was 21.03 mmol H2/(l × h) using 3% xylose as substrate [53]. The yield, after 5 h HRT, was 2.36 mol of H2 per mole of xylose.


WATER GAS SHIFT REACTION :WATER GAS SHIFT REACTION Certain photoheterotrophic bacteria within the superfamily Rhodospirillaceae can grow in the dark using CO as the sole carbon source to generate ATP with the concomitant release of H2 and CO2 [35–37]. The oxidation of CO to CO2 with the release of H2 occurs via a water–gass hift reaction: CO(g) + H2O(l) ? CO2(g) + H2(g); dG= - 20 (kJ/mol). The reaction is mediated by proteins coordinated in an enzymatic pathway & takes place at low (ambient) temperature and pressure


Slide 18:The enzyme that binds & oxidizes CO, carbon monoxide:acceptor oxidoreductase (carbon monoxide dehydrogenase = CODH) is part of a membrane bound enzyme complex [37,38]. Rubrivivax gelatinosus CBS is a purple non-sulfur bacterium that not only performs the CO–water–gas shift reaction in darkness, Converting 100% CO in the atmosphere into near stoichiometric amounts of H2, It also assimilates CO into new cell mass in the light (via CO2 fixation) when CO is the sole source of carbon [39,40].


Slide 19:The hydrogenase from this organism is tolerant to O2, exhibiting a half-life of 21 h when whole cells were stirred in full air [43]. Because the conversion of CO to H2 is stoichiometric, this corresponds to a rate of CO uptake and conversion of approximately 1:34 g CO/h/g cdw, or 48 mmol CO/h/g dcw. This corresponds to a H2 production rate of 96 mmol H2=2 g cdw/h or 96 mmol H2/(l × h).


FUEL CELL TECHNOLOGIES :FUEL CELL TECHNOLOGIES Fuel cells are electrochemical devices that create an electron flow using charged ions. A variety of different fuel cells systems have been developed. They differ in the type of electrolyte used, in the operating conditions, in their power density range, in their application, and Each has its advantages and disadvantages (reviewed by Larminie et al. [7];Table 3).


ALKALINE FUEL CELL :ALKALINE FUEL CELL Utilize hydroxyl ions(OH -) as the mobile ion (derived from potassium hydroxide, KOH)? Operate in the 50 to 200?C range The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues.


PHOSPHORIC ACID FUEL CELL :PHOSPHORIC ACID FUEL CELL Utilize protons(H +) as the mobile ion & operate at approximately 200?C. PAFC systems were the first fuel cells produced commercially and are used as stationary power sources, generating up to 200 kW of electricity. The high operating temperature and corrosive nature of the electrolyte makes them unsuitable for use in mobile and transportation applications.


Slide 23:They are 85 percent efficient when used for the co-generation of electricity and heat, but less efficient at generating electricity alone (37 to 42 percent). Require an expensive platinum catalyst, which raises the cost of the fuel cell. A typical phosphoric acid fuel cell costs between $4,000 and $4,500 per kilowatt to operate. The phosphoric acid fuel cell (PAFC) is considered the "first generation" of modern fuel cells. PAFCs are more tolerant of impurities in fossil fuels that have been reformed into hydrogen than PEM cells, which are easily "poisoned" by carbon monoxide


MOLTEN CARBONATE FUEL CELL :MOLTEN CARBONATE FUEL CELL Utilize carbonate ions as the mobile ion, Operate at approximately 650?C, Can take H2, CO2, CO, and/or CH4 as fuel, which means they can use natural gas, coal gas, or biogas as fuel sources. Are used as stationary power sources, generating electricity in the MW range.


SOLID OXIDE FUEL CELL (SOFC)? :SOLID OXIDE FUEL CELL (SOFC)? Utilize oxygen radicals as the mobile ion Operate between 500 - 1000?C. Can utilize H2, CO, and/or CH4 as fuel, which mean they can use methane, coal gas, or biogas as fuel sources. Carbon dioxide is not utilized as a fuel and is discharged as a waste gas Are used as stationary power sources, generating electricity from the low kW to MW range High temperature operation removes the need for precious-metal catalyst, thereby reducing cost.


PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFC)? :PROTON EXCHANGE MEMBRANE FUEL CELL (PEMFC)? Utilize H+ as the mobile ion, Operate in 50–100?C range Require pure H2 and are extremely sensitive to the presence of CO. Of all the fuel cell systems that are available, PEMFC systems are especially suitable for mobile and transportation applications. PEMFC engines have been demonstrated successfully in both cars and buses. Small PEMFCs, in 1–10 kW range, are also under commercial development as small stationary power units to provide electricity to homes & small businesses.


Slide 27:PEM fuel cells use a solid polymer as an electrolyte and porous carbon electrodes containing a platinum catalyst. They need only hydrogen, oxygen from the air, and water to operate and do not require corrosive fluids like some fuel cells. They are typically fuelled with pure hydrogen supplied from storage tanks or on board reformers. Low temperature operation allows them to start quickly (less warm-up time) and results in less wear on system components, resulting in better durability. However, it requires that a noble-metal catalyst (typically platinum) be used to separate the hydrogen's electrons and protons, adding to system cost. The platinum catalyst is also extremely sensitive to CO poisoning, making it necessary to employ an additional reactor to reduce CO in the fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel. This also adds cost. Developers are currently exploring platinum/ruthenium catalysts that are more resistant to CO.


CONCLUSIONS :CONCLUSIONS Photosynthesis-based systems do not produce H2 at rates that are sufficient to meet the goal of providing enough H2 to power even a 1 kW PEMFC on a continuous basis (Table 5) . Hydrogen production by direct photolysis using green algae is currently limited by three parameters[ 60]: (i) solar conversion efficiency of the photosynthetic apparatus; (ii) H2 synthesis processes (i.e. the need to separate the processes of H2O oxidation from H2 synthesis)? (iii) bioreactor design and cost DOES THIS MEAN THAT THIS METHOD BE ABANDONED ? genetic engineering of light gathering antennae [61], optimization of light input into photobioreactors [62], Improvements to the two-phase H2 production systems used with green algae [63,64].


Slide 34:Thermophilic and extreme thermophilic biohydrogen systems would require bioreactors in the range of approximately : 2900–14,600 l to provide sufficient H2 to power PEMFCs of 1.5–5:0 kW, A bioreactor of approximately 5700 l would be required to power the 5:0 kW fuel cell using the pure culture of mesophilic Clostridium sp. (strain No. 2). The size of bioreactors required for these systems are very large, and thus these systems may be considered impractical for our hypothetical application at this time.


Slide 35:Some dark-fermentation systems and the CO–water shift reaction of R. gelatinosus CBS, however, appear promising. Bioreactors of reasonable size would be sufficient to power the 5.0 kW fuel cell using undefined consortia of mesophilic bacteria, enriched for Clostridium species. The system reported by Chang et al. [55] in particular appears most promising. A bioreactor of approximately 500 l (495 l, in Table 5) would provide enough H2 to power a 2.5 kW PEMFC, while a bioreactor of approximately 1000 l (989 l, Table 5) would provide .sufficient Hydrogen to power a 5 kW PEMFC.


Slide 36:While dark-fermentation systems and the CO-water shift reaction may have practical applications, there are a number of technical challenges that must be considered and overcome before these systems can be used to produce H2 to power a PEMFC. The most significant of these problems is whether the systems can be scaled up to volumes large enough to generate the required Uow rate (22:1 mol H2/h for the 5:0 kW fuel cell).


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ACKNOWLEDGEMENTS :ACKNOWLEDGEMENTS I WOULD SINCERELY LIKE TO THANK THE FOLLOWING PEOPLE WHOSE HELP & GUIDIANCE ENABLED ME PREPARE THIS PRESENTATION :? Prof. M.K. Mahanti , ( NISER)? Dr. Harapriya Mahapatra, ( NISER)? Dr. Rajendra Behera, ( NISER)? Prof. Rabindranath Nayak , ( NISER)? Prof. Santosh Kar , ( NISER) Mr. Abhisek Dwivedy (My partner in Biohydrogen Project)? Mr. Sourajit Soumyaranjan Das (My partner in Hydrogenase Project)?