BIOHYDROGEN

Presented by:

Mr.Darshan GowdaBTL(H)007

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Contents

Introduction

Hydrogen properties

Hydrogen production methods

Bio hydrogen & its

History

production methods

Economics

Conclusion

Reference

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Why we need alternative fuel.?

Fossil fuel resources

are

Limited

green house gases

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Understanding the hydrogen

Hydrogen is the first element on the periodic

table, making it the lightest element on earth.

0.00005% in air

It rises in the atmosphere and is therefore rarely

found.

pure hydrogen gas, burning in air, producing

water and heat.

Combustion heat enables hydrogen to act as a

fuel.

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Hydrogen properties

Colorless and odorless

Extremely reactive with oxygen and other

oxidizers.

Low ignition energy.

High flame temperature.

Invisible flame in daylight conditions.

Small molecular size promotes leaks and diffusion.

The cryogenic liquid at 20K is even colder than frozen nitrogen, oxygen or argon.

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Key facts about Hydrogen as a fuel

Highly combustible and can be used as a fuel.

1g of combustion provides 30000 cals as compared to gasoline

that gives only 11000 cals.

Can be produced from water using Biological agents.

Biologically produced hydrogen is known as Biohydrogen.

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Hydrogen Production

1. Electrolysis.

2. Steam-methane reforming process.

3. Biological process(bio-hydrogen).

Hydrogen production always requires more

energy than can be retrieved from the gas as

a fuel later on when they are produced by above

two process.

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Simple setup for demonstration

of electrolysis of water.

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Biological production

Biological hydrogen production stands out as

an environmentally harmless process carried

out under mild operating conditions, using

renewable resources.

Several types of microorganisms such as the

photosynthetic bacteria, cyano bacteria, algae

or fermentative bacteria are commonly utilized

for biological hydrogen production.

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Milestones

1939 Hans Gaffron discovered that algae can switch

between producing O2 and H2.

1997 prof. Anastasios Malis discovered that deprivation of

sulphur will cause the algae to switch from producing

H2.He found that enzyme hydrozenase responsible

for the reaction.

2006 Researcher from the University of Bielfeld have

genetically changed the single cell Chlamydomonas

reinhardtiiin in such a way that it produces an large

amount of hydrogen.

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2007 It was discovered that if cupper is added to

block O2 generation in algae.

2007 prof. Anastasios Malis studying solar to chemical

energy conversion efficiency in tax X mutants of

Chlamydomonas reinhardtiiin , achieved 15% efficiency .

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Methods of Bio hydrogen Production

1.Dark Fermentation

2.Photo Fermentation

3.Combined Fermentation

4.Direct Photolysis (algae)

5.Indirect Photolysis (cynobacteria)

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1. Dark Fermentation

Fermentative conversion of organic substrate to

biohydrogen.

This method doesn’t require light energy.

The Gram+ve bacteria of Clostridium genus is of

great potential in biohydrogen production.

Require wet carbohydrate rich biomass as a

substrate.

Produces fermentation end product as organic

acids, Co2 along with biohydrogen.

C6H12O6 + 2H2O 2CH3COOH + 4H2 +

2CO2

(Butyrate)

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Glu pyruvate acetylcoA fdH2

Carbohydrate mainly glucose is preffered.

Pyruvate the product of glucose catabolism is oxidized to

acetyl-coA requires ferrodoxin reduction.

Reduced ferrodoxin is oxidized by hydrogenase which

generates ferrodoxin and release electron as a molecular

hydrogen.

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Advantages

It produces valuable metabolites as a butyric acid,propionic acid.

It is an anaerobic process so no oxygen limitation.

It can produce carbon during day and night.

Variety of carbon sources can be used as a substrate.

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Drawbacks

Relatively lower achievable yield of H2, as a portionof substrate is used to produce organic acids.

Anaerobes are incapable of further breakdown ofacids.

Accumulation of this acids cause a sharp drop ofculture pH and subsequent inhibition of bacterialhydrogen production.

Product gas mixture contains Co2 which has to beseparated.

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Approaches to overcome

Metabolic shift of biochemical pathway to

arrest the formation of acid and alcohol.

To improve the techniques for the seperation of

the gases.

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2.Photo Fermentation

Purple non sulphur bacteria genus rhodobacter

holds significant promise for production of

hydrogen.

Photo fermentation where light is required as a

source of energy for the production of hydrogen

by photosynthetic bacteria.

Organic acids are preferred as a substrate.

The light energy required in this process is

upto the range of 400nm.

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MechanismCH3COOH + 2H2 + Light 4H2 + 2Co2

Production of hydrogen by photosynthetic

bacteria takes place under illumination and in

the presence of inert and anaerobic atmosphere

for the breakdown of organic substrate to

produce hydrogen molecules.

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Advantages

Relatively higher achievable yield of H2, as aportion of substrate is used to produce organicacids.

Anaerobes are capable of further breakdown ofacids in to biohydrogen.

Drawbacks

It can produce carbon during day only.

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Combined fermentation

The combination of dark and photo fermentation

provides an integrating system for maximization of an

hydrogen yield.

The idea of combined fermentation takes into an

consideration the very fact of relatively lower achievable

yield of H2 in dark fermentation.

The non utilization of acid produced in dark

fermentation.

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Mechanism

Stage 1 :- Dark fermentation:-

Anaerobic fermentation of carbohydrate

produces intermediates such as low molecular

weight organic acids and Co2 along with

hydrogen.

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Stage 2:- Light fermentation

The low mol wt organic acid in stage 1 are converted to hydrogen

by photosynthetic bacteria.

2CH3COOH + 4H2o CH3COOH + 2Co2 + 4H2

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Advantages

Two stage fermentation can improve the

overall yield of hydrogen and overcomes the

major limitation of dark fermentation.

Drawbacks:-

Relatively new approach techno economic

feasibility is yet to studied

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4.Direct Photolysis

Certain green algae produces H2 under anaerobic

condition.

Under deprived of S green algae Chlamydomonas reinhardtiiin

become anaerobic in light & commence to synthesis of

hydrogen.

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Direct Photolysis

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Molecular aspects

Light Absorption by Photo system II (PSII) Initiates thePhotosynthetic Pathway.

PSII is a large molecular complex that contains severalproteins and light-absorbing pigment molecules likecarotenoids, chlorophylls and phycobilins.

The reaction center strips electrons from two watermolecules, releasing four protons and an oxygen (O2)molecule into the thylakoid space.

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The electron carrier from PSII passes through thethylakoid membrane and transfers its electrons to thecytochrome complex, which consists of severalsubunits including cytochrome f and cytochrome b6.

A series of redox reactions within the complexultimately transfer the electrons to a second electroncarrier i.e. photo system I (PSI).

As electrons are transported through the complex,protons (H+) outside the thylakoid are carried to theinner thylakoid space.

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Light Absorption by PSI Excites Electrons and FacilitatesElectron Transfer to an Electron Acceptor Outside theThylakoid Membrane.

Light absorbed by the PSI reaction center energizes anelectron that is transferred to ferredoxin (Fd), a moleculethat carries electrons to other reaction pathways outside thethylakoid.

The reaction center replaces the electron transferred toferredoxin by accepting an electron from the electron-carriermolecule that moves between the cytochrome and the PS1

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Under Certain Conditions, Ferredoxin canCarry Electrons to Hydrogenase.

Normally, ferredoxin shuttles electrons to anenzyme that reduces NADP+ to NADPH, animportant source of electrons needed to convertCO2 to carbohydrates in the carbon-fixingreactions.

Under anaerobic conditions, hydrogenase canaccept electrons from reduced ferredoxinmolecules and use them to reduce protons tomolecular hydrogen (H2).

4H+ + ferredoxin(oxi) ――› ferredoxin(reduced) + 2H2

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Algae Recycle

Nutrient recycle

Sunlight

SunlightA LGAE

Hco2 o2

Algae production Bioreactor (Light Aerobic)

Algae Concentrator and adapter (Dark-Anaerobic)

H2 Photobioreactor(light anerobic)

Fig:- Schematic of Hydrogenase mediated Biophotolysis process

H2

H2

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Economics The US department of energy has targeted a selling price

of $2.60/kg as goal for making renewable hydrogen

economically viable.

1kg is approximately the energy equivalent to a gallon of gasoline.

To achieve this , the efficiency of light to hydrogen

conversion must reach 10% while current efficiency is only

1% and selling price is estimated at 13.53/kg.

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Reference

Hand book of bioenergy and biofuels – V K mutha

Journal on Bio hydrogen production aspotentialenergy resources by Kaushik & D Das.

Bio biohydrogen – Microbiological production of

hydrogen fuel by P C Hallebeck & J R Bennemen

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Conclusion Bio hydrogen is fuel of future

Areas of research to increase efficiency include developing

of oxygen tolerant hydrogenase and increased hydrogen

production rates.

Research on cost effective production of bio hydrogen for

commercialization is required.

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Thank you