Hydrogen.gov | A. Biological Processes

A. Biological Processes

1. Biomass Processes

a) Water-gas CO shift (WGS)
Goals: Production rate, Durability, efficiency of conversion, low CO in reformate

i. Study biological systems of WGS in order to determine alternative shift pathways.
Goals: Identify the relevant genetic components; Enable manipulation of gene expression.

ii. Single-step shift
Goal: Integrate WGS with membrane separation technology.

b) Catalysts
Goals: Efficiency, Impurity tolerance, lower cost

i. WGS shift catalysts

ii. Reformer catalysts

iii. Catalysts for fluid-bed reforming of biomass pyrolysis liquid

c) High-temperature membranes
Description: Requires no added catalyst.

d) Bioreactors
Goals: Increase hydrogen yield to levels commercially viable.

i. Develop new fermentative micro-organisms.

e) Oxygen Separation Technologies for Gasification and Reforming
Goals: Efficiency, Impurity tolerance

i. Air separation technologies

ii. Integrated oxygen membrane/reactor systems

f) Pyrolysis
Goal: Reduce cost and improve hydrogen yield

i. Feedstock preparation and handling systems

ii. Heat integration improvements

iii. Vapor conditioning

iv. Co-product opportunities

v. Integrated reforming and shift processes

a. Demonstrate proprietary microscale reactor.

g) Gasification
Goal: Reduce cost

i. High-pressure gasification systems (10-30 atm)

ii. Heat integration improvements

iii. Feedstock preparation and handling systems

iv. Integrated reforming and shift processes

h) Gasifier product gas clean-up
Goals: Cost, Efficiency, Durability
Description: for feed into reforming operations.

i. Hot-gas clean-up

ii. Tar-cracking

i) Catalytic steam reforming
Goals: Improve reforming efficiency and lower cost through improved catalysts and better integration of available heat.

i. Fluid-bed reforming catalysts

ii. Gasifier product gas reforming and conditioning catalysts

iii. Pyrolysis oil vapor and fractions conditioning catalysts

iv. Heat integration

v. Improved reactor configuration

j) Gas separation technologies
Description: Develop and characterize new porous materials to remove sulfur-containing compounds and carbon monoxide from the hydrogen stream.

i. Microporous oxides

ii. Metal-organic frameworks

iii. Carbon sorbents

k) Thermodynamic analysis
Description: Develop a predictive model for thermodynamic properties for biomass reforming, including pressure, volume, temperature, heat capacity, viscosity, and thermal conductivity, of hydrogen + hydrocarbon (methane, ethane...) + CO2 + alkanol (methanol, ethanol....) + water mixtures.

l) Carbon sequestration

m) Materials Description: acidic or basic processes

n) Membrane testing
Description: Establish test methods and standard membranes to ensure reliable comparisons of gas separation technologies.

o) Aqueous-phase carbohydrate reforming
Description: This process can generate hydrogen at temperatures near 500 K via the aqueous-phase, catalytic reforming of biomass-derived oxygenated compounds such as ethylene glycol, glycerol, sugars and sugar-alcohols, which are nonflammable, non-toxic, transportable liquids. This process generates hydrogen without the need to volatilize water (and thus is more efficient than conventional steam reforming), and the water-gas shift reaction is favorable for low CO concentrations, making it possible to use a single chemical reactor.

2. Fermentative Production
Description: Includes both mesophilic and thermophilic organisms, in mixed culture anaerobic processes

a) Nutrients

i. Phosphogypsum

b) Reactor
Description: Develop continuous flow reactors with complex wastes.

c) Enzymatic catalysis
Description: Study hydrogenase and related enzymes wrt catalytic mechanism and sensitivity to inhibitors.

d) Genetic and metabolic pathways

i. hydrogenotrophic (e.g., methanogens)

ii. hydrogenogenic (e.g., sulfate-reducing bacteria)

e) Electron transfer and redox pathways

f) Novel substrates and cofactors
Description: Identify and characterize.

i. Cellulose-rich substrates

ii. Influence of environmental conditions such as pH, T, substrate concentration, and mixing.

iii. Effect of germination and sporulation life cycle of clostridia.

g) Micro-organisms
Description: Identify and characterize higher-yield organisms.

i. Develop a nucleic-acid based probe.

3. Photobiological Production

a) Molecular genetics and metabolics
Goals: Oxygen tolerance, Light-conversion efficiency, Photosynthetic electron transport efficiency

i. Use screening methods to identify candidate photosynthetic bacteria.

ii. Measure the specific CO shift kinetics of various photosynthetic bacteria.

a. Rubrivivax (Rx.) gelatinosus CBS.

b. cloned Chlamydomonas reinhardtii hydrogenases

iii. Mutant hydrogenase genes

a. Determine which enzymes are related to O2-tolerant mutants.

b. Use random or site-directed mutagenesis based on information obtained from structural analyses.

iv. Characterize and regulate genetic and metabolic pathways.

v. Redox potential measurement Goal: Support high-throughput screening technologies. Description: Develop redox potential measurement methods and provide fundamental data on enzymatic oxidation-reduction potential.

b) Chlorophyl and other photoactive pigments
Goals: Optimize biophysical parameters for improved irradiance response and solar energy conversion.

c) Enzymes
Description: Study enzymes with respect to sensitivity to oxygen and other inhibitors.

i. Hydrogenase

ii. Nitrogenase

iii. Other

d) Electron transfer and redox pathways
Description: Characterization study

e) System design

f) Reactor design

g) Hydrogen collection and oxygen separation technologies

h) Gas separation technologies

i) Analysis

i. Economic

ii. Technical

4. Energy-Coupled Systems and Bioenergetics

a) Syntrophic associations

b) New biological organisms and microbial communities

c) Bioenergetics of single and mixed systems

5. Feedstock Production

a) Forest biomass Description: Short rotation wood crops, small-diameter trees

i. Management systems

ii. Economics in rural economies

iii. Harvest technologies

iv. Genetic development

v. Characterization

b) Agricultural biomass

i. Dairy, pig farm waste

ii. Aquaculture farm waste

ii. Cheese processing waste

6. Demonstrations

a) Fueling station Description: Incorporate promising technologies into an integrated H2 production, building power, and fueling system, at distributed locations (see V.D.2 for a complete description).
Goal: Evaluate efficiency, durability, and gain real-world experience.

i. Landfill gas feedstock cleanup

ii. Anaerobic digester gas feedstock

b) Biomass gasification

c) Biomass fermentation

d) Algal production

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