photoinduced bio hydrogen production from biomass

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Photo-induced Biohydrogen production from Biomass - Abhisek Dwivedy National Institute of Science Education & Research Bhubaneswar

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A Brief Layout 1. Biomass- a renewable source of energy 2. Composition & Type of biomass 3. Biomass conversion- non Biological processes 4. Biomass conversion- Biological processes 5. Photo induced Biohydrogen production from Biomass

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Biomass- A renewable source of energy What is Biomass? Biomass refers to living and recently dead biological material that can be used as fuel or for industrial production. It refers to all living or dear cellular mass that can be used to generate power or fuels. It excludes all organic materials that have been transformed by bio geochemical process i.e. Coal or petroleum. Biomass can be used as fuel directly by combustion, can be fermented to produce ethanol, biogas, methane. Destructive distillation of biomass yields oil gas, charcoal etc. Biomass can be used for large scale production of hydrogen which can be a convenient biofuel in near future.

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Composition of Biomass Major portion of biomass is constituted of cellulose, Hemicellulose (xylans, arabinose, galactose & glucose), lignin (p-hydroxy cinnamyl alcohol), fats, oils, resin, pigments, nucleic acids and proteins. Biomass can be terrestrial(forests, agricultural crops etc) as well as aquatic. The major aquatic biomass are the weeds like Salvinia , Eicchornia etc. Marine biomass includes phytoplanktons & zooplanktons. Organic wastes also add to biomass. The major sources of wastes are paper mill (lignocellulosic wastes), oil refineries(gas, oil, paraffin, olefins etc), cotton mills (seeds & fibers). Food & Dairy industries also produce large no of organic wastes. Sugarcane mills produce wastes like molasses & bagasse etc. The lefts overs after agricultural harvests also add to biomass. Municipal & urban wastes i.e sewage & sludge also have organic contents that can be used for energy purposes.

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Biomass Conversion Conversion of biomass into energy can be achieved in a number of ways. There are broadly two ways of conversions i.e 1. Biological process 2. Non biological process Biomass Conversion Non Biological Processes Biological Processes 1. Direct combustion 2. Pyrolysis 3. Gasification 4. Liquefaction 1. Enzymatic digestion 2. Anaerobic Digestion (fermentation)‏ 3. Aerobic methods

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Non Biological Processes 1. Direct Combustion : Direct burning to biomass to produce heat energy. e.g: fuel wood from energy plantations; hog fuel i.e. Direct burning of wood and bark in huge incinerators # Energy Plantation is the practice of planting trees purely for use as fuel wood. 2. Pyrolysis : Destructive distillation of biomass like saw dust, wood chips & pieces etc at temperatures about 200*C-500*C produces charcoal, pyroligneous acid, methane gas etc. 3. Gasification : In this process organic matter is degraded thermally at temperatures higher than 1000*C under controlled air supply to give low molecular weight aromatic gaseous compounds. e.g: hydro gasification of farm wastes 4. Liquefaction : Organic wastes are made to react with carbon monoxide and water at high temperature & pressures producing oils of high fuel value.

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BIOGAS PLANT

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Updraft Gasifier Downdraft Gasifier Twin Fire Gasifier Cross draft Gasifier GASIFIERS

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WOOD to BIODIESEL

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Biological processes 1. Enzymatic digestion : This is the main process involved in conversion of cellulose & Hemicellulose into bio fuels. This is achieved with the help of micro organisms like Cellulomonas , Trichoderma etc. The reactions involved are catalyzed by catalysts like cellulase, β -1,4 endogluconase, β -1,4 exogluconase, cellobiase. Cellulose Oligomers of glucose Cellobiose Glucose 2. Fermentation : It is the anaerobic digestion of organic substrates in absence of air by microorganisms. It is useful production of bio gas, methane, ethanol, bio hydrogen. Commonly used micro organisms are yeast, filamentous fungi, bacteria. e.g: Methanobacterium , Methanococcales , Methanomicrobiales Complex organic matter Fatty acids & alcohols acetate Water + carbon dioxide formate Carbon dioxide Methane + carbon dioxide Methane + water Production of Methane Cellulose degradation

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Corn to Ethanol

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3. Aerobic Methods : Photosynthesis the natural process of biomass production. Along with carbohydrates what we get as a by product is hydrogen. Similarly huge amount of hydrogen is released to atmosphere as a by product during Nitrogen fixation by free living and nitrogen fixing bacteria and cyanobacteria. It is estimated that about 30 billion cubic meters of hydrogen is lost annually from soybean plantations of US.

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Hydrogen thus produces can directly be used as fuel to run turbines or can be converted to water in a fuel cell to directly generate electricity. As calorific value of combustion of hydrogen is much higher than carbon and the end product is water it can be preferentially used over fossil fuels.

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Photo induced biohydrogen production from biomass Biomass contain mixed saccharides like sucrose, maltose, cellulose, cellbiose. When such mixed saccharides are hydrolyzed enzymes they yield glucose as the final product. Glucose is chemically converted to gluconic acid by enzyme glucose dehydrogenase (GDH). Since NAD+ acts as cofactor for GDH, it gets converted to NADH. NADH is made to donate an electron to a photosensitizer along with release of that H+ which in turn gets excited by light energy to a higher oxidation/higher energy state. This excited photosensitizer is then made to transfer its electron to an electron carrier which supplies the electron to protons in presence of enzyme hydrogenase to release hydrogen.

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Commonly used photosensitizer is zinc tetra phenyl porphyrin tetra sulfonate These type of zinc porphyrins usually show absorption at about 500-600 nm though the value is higher in ultra violet region i.e. 380-400nm. Most commonly used electron carrier is methylviologen i.e. MV+ Since the whole process is carried out in a colloidal medium containing glucose & gluconic acid under appropriate light & aerobic conditions hydrogenase is never used as it sensitive to oxygen. Instead a platinum or palladium compound is used as catalyst with NADH as electron donor. The overall process converts H+ from glucose and gives out H2. This is totally a non biological process copying a natural process.

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Generalized figure of the process

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* The whole experiment is carried out in a phosphate buffer medium kept at pH of 7.0. # Recently some zinc porphyrin compounds were also introduced as photosensitizer as they were more sensitive to light. Some of them are: Zn-Bacteriochlorophyll a from Acidiphillium rubrum Mg-Chlorophyll a from green algae # Though the above mentioned compounds were more sensitive to light the rate of hydrogen production was best in the artificial zinc compound: Photosensitizer Rate of H2 production ( µmol/hr)/MV+ (µmol/min)‏ 1. Mg Chl-a 0.61/0.0025 2. Zn Bchl-a 1.75/0.0086 3. Zn-TPPS 2.57/0.014

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Detailed figure for the process explained

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Since the biomass we generally use in such a process is mostly cellulose containing the primary job is to convert cellulose to methyl cellulose which in turn is converted to methyl glucose using enzyme cellulase. The production of hydrogen an rate to e- transfer by MV was found to be independent of molecular weight of methyl cellulose used. The following data shows the variance of H2 production with molecular weight of methyl cellulose used: Rate of Production Mol. Wt of Methylcellulose H2( µmol/hr)/MV+(µmol/min)‏ 15,000 2.9/0.0060 21,000 3.0/0.0061 26,000 2.3/0.0058 41,000 3.0/0.0060 63,000 2.9/0.0060 86,000 2.8/0.0059

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At last similar experiment was carried out using different experimental setups each having a different saccharide component. This was done to verify the best substrate that can be used for large scale hydrogen production by this artificial method. The following results were obtained: Rate of production of Saccharide used H2( µmol/hr)/MV+(µmol/min)‏ D- maltose 1.23/ 0.0045 Methyl cellulose 3.00/ 0.0060 Mixture of sucrose, 1.45/ 0.0040 D- maltose, cellobiose # Thus it was concluded that the above method was best suited for degradation of cellulose to produce hydrogen in most economical manner.

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BIOFUEL- BENEFITS Environmental Benefits Reduction of waste Extremely low emission of greenhouse gases compared to fossil fuels Ethanol is Carbon neutral and forms a part of the carbon cycle Growing variety of crops increases bio-diversity Socio-Economic Benefits Helps developing economies by promoting agrarian communities Increase in jobs Increase in trade balance (Indian perspective) due to lesser dependence on foreign resources

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Conclusions : Thus we can conclude that biomass can be used as a source of energy for various purposes in various different manners. Since biomass is recycled in nature it can used over and over again. Finally bio hydrogen, which is the most economical & environment friendly fuel, can be conveniently produced by special method of biomass conversion. The only problem that we are currently facing is the storage of hydrogen. Proposed methods of storage are in form of liquid H2 under high pressure. Similarly currently research showed that Rhodium(I) co-ordinate compounds having phosphine ligands can be used as storage for hydrogen. Thus I would like to conclude my talk with a hope that soon we will be able to produce, store & use bio hydrogen as the most economical future fuel for industrial, automobile and domestic purposes as well.

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References 1. Photo-induced biohydrogen production from Biomass [International Journal of Molecular Sciences, July 2008] -Yutaka Amao 2. A textbook of Biotechnology [Uppala Author Publisher Interlinks] -U Satyanarayan 3. A textbook of Biotechnology [S Chand Publications] -R C Dubey

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FIGURE REFERENCES http://www.alternate-energy-sources.com/images/biomasscorntoethanol.gif http://www.eia.doe.gov/kids/energyfacts/sources/renewable/images/BIOMASSTYPES1.gif http://www.eubia.org/uploads/RTEmagicC_Conversion_routes_01.TIF.jpg http://www.aist.go.jp/aist_e/latest_research/2006/20060418/20060418.jpeg http://biotech.szbk.u-szeged.hu/images/bf_kk_f2.jpg http://www.nature.com/nbt/journal/v22/n1/images/nbt0104-40-F1.jpg http://www.aebiom.org/IMG/bioenergy%20routes2.JPG

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Thank You....