hydrogen from algae nanotechnology solutions foothill college bio-nano-info program
TRANSCRIPT
Hydrogen Metabolism
H2S 2H + S H2O H + OH H2 2 H + 2e-
In photosynthesis (simplified):
H20 H + OH + 2e-
2H + CO2 CH2O OH + OH H2O + O 2O + 2e- O2
Life on Earth
Timeline for development of the major life forms.
From a course site by Robert Huskey, U. Virginia
Hydrogenase
• Biological cleavage of H2 is a common metabolic process in prokaryotes and lower eukaryotes and is catalyzed by two major classes of enzymes the [NiFe]- and the [Fe]-hydrogenases.
• Three distinct [NiFe]-hydrogenases of Ralstonia eutropha (formerly Alcaligenes eutrophus) are in the center of this project, the regulatory (RH), the NAD-linked (SH) and the membrane-bound (MBH) hydrogenase
Fossilized Blue Green Algae
These filaments are believed to be the fossilized imprints of blue-green algae, one of the earliest life forms. They occur in the Bitter Springs Formation in Australia and are about 850 million years old.
In Vitro Photo-Production of H2
Yellow arrow marks insertion of hydrogenase promoter. Right side exp. optimized for continuous H2 production.
Production of H2 From Algae
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/iic2_lee.pdf
H2 Energy Calculations
Assumptions were made that 10 micro mole of H2 can be produced per hour (roughly 50% of peak maximum but extended for an hour) per mg of chlorophyll. Additionally, a density of 10% of the top 1 cm (or 100% of top mm) of the system would be populated by chlorophyll, for a density of 1 mg chlorophyll per square cm of collector. This leads to 10,000 cm multiplied by 10 mg chlorophyll per centimeter for a total of 100,000 mg chlorophyll. Multiplying 100,000 mg chlorophyll by 10 micromole H2 generated per hour per mg chlorophyll yield 1 mole of hydrogen gas per square meter per hour. Combusting one mole of H2 with one half mole of oxygen (H2 + ½ O2 H2O) yields 286 KJoules or 68 Kcal. Using any of the following conversions yields KWatt hours or watts from this reaction: 1 calorie = 4.184 Joules1 calorie = 0.0011622 KwHr1 Joule = 0.0002778 Watt hours1 K Joule = 0.2778 watts 286 KJoules X 0.2778 Watts / KJoules = 79 Watts 68,355 calories X 0.0011622 KwHr per calories = 79 KwHr On first pass, it appears that 1 square meter of hydrogen producing algae (modified for continuous hydrogen production) yields about 79 watts, or enough to run a 75 watt light bulb at full power.
ORNL Project Road Map
• Year 1- Design and construction of DNA sequence coding for polypeptide proton channel
• Year 2 - Genetic transfer of hydrogenase promoter-linked polypeptide proton-channel DNA into algal strain DS521
• Year 3 - Characterization and optimization of the polypeptide proton-channel gene expression
• Year 4 - Demonstration of efficient and robust production of H2 in designer alga (ready for next phase - scale-up and commercialization)
Genetic / Biochemical Engineered H2 Bacterium
• Sequence coding for polypeptide proton channel – create gene for proton pump
• Genetic transfer of hydrogenase promoter-linked polypeptide proton-channel DNA into algal genome – express pump with H2
• Characterization and optimization of the polypeptide proton-channel gene expression
Proposed Engineered H2 Bacterium
http://gcep.stanford.edu/pdfs/tr_hydrogen_prod_utilization.pdf
Polypeptide Proton Channel
• Protons that build up from cleavage of H2O into H atoms repress hydrogenase reaction
• Need to pump hydrogen atoms away from the photosynthetic reaction core, and into storage
• Hydrogen storage in a carbon nanotube can be the first stage in a nano-structure fuel cell– Platinum doped carbon nanotubes might be an
integrated device: storage, fuel cell, and battery
Membrane Bound Protein Pumps
Proton and ion pumps consumea lot of cellular energy
Nano-channels could be useful
Nanotubes / Nanohorns
The electrical properties of nanotubes / nanohorns can change, depending on their molecular structure. The "armchair" type has the characteristics of a metal; the "zigzag" type has properties that change depending on the tube diameter—a third have the characteristics of a metal and the rest those of a semiconductor; the "spiral" type has the characteristics of a semiconductor.
Nanotube Properties
http://nanotech-now.com/nanotube-buckyball-sites.htm
Hydrogen Fuel Cell Basics
http://micro.magnet.fsu.edu/primer/java/fuelcell/
Hydrogen Fuel Cell Diagrams
Schematic representation of acomposite electrode for low temperature fuel cells
Schematic representation of themembrane electrode assembly
http://www1.physik.tu-muenchen.de/lehrstuehle/E19/research/pefc.html
Summary
• Hydrogen metabolism is ancient, and highly conserved in hydrogenase / photosynthesis
• With genetic / biochemical engineering, algae can make H2 in significant amounts
• Capturing and wicking of H2 into a carbon nanotube fuel cell / battery is very feasible
• A 1 sq. meter collector could power a 500 watt household with ~ 10X technology gain