Photobiological Hydrogen Production – uses microorganisms to convert solar energy into hydrogen.
Advantages of hydrogen:
- Hydrogen is the most abundant element in the Universe, but not in the form of H2.
- Hydrogen also has a large gravimetric energy density (higher than methane and oil)
- Does not emit CO2.
- PEM (Proton Exchange Membrane) fuel cells are 40-60% efficient.
Disadvantages of hydrogen:
- Storing hydrogen is very expensive
- Hydrogen needs to be compressed.
- fuel cells have high expenses and are not reliable.
Hydrogen is produced from: 48% natural gas reforming, 30% from oil refining, 18% from coal refining, and 4% from water electrolysis.
Photobiological Hydrogen Production eats up CO2, and the only products are O2 and biomass. So it is renewable and sustainable. Maximum theoretical light to H2 conversion efficiency is 41% efficient using hydrogenase enzymes, and economically viable at 10%.
Disadvantages of Photobiological Hydrogen Production
- needs water
- Low efficiency due to low amounts of sunlight, presence of oxygen (needs to be removed), presence of nitrogen, and large partial pressures of hydrogen.
- Difficulty in scaling up.
There are 4 different species of microorganisms: green algae, cyanobacteria, purple non-sulfur bacteria, and dark fermentative bacteria.
ATP (Adenosine-5’-triphosphate) – energy source in the cell
NADP+ – coenzyme used in lipid synthesis.
Photosynthesis – converts CO2 into organic compounds. First step: light dependent reaction – converts sunlight into chemical energy (ATP and NADPH). Second step: Dark reactions convert CO2 and H2O into organic compounds.
Enzyme – protein that catalyze chemical reactions
Nitrogenase – converts N2 into NH3. The turn over rate is 10 reactions /s.