»Biological catalysts for the generation of H2 /Page 4
~ found in microorganisms such as unicellular green algae, cyanobacteria, photosynthetic bacteria, and in some forms of dark fermentative bacteria

Sunlight
~ as a source of energy is Clean and Unlimited
~ but it is also diffuse, averaging 4.2 kWh per square meter per day in the US
~ assuming a1 0% solar conversion efficiency to hydrogen, it was estimated that about 5,500 square miles of surface area would be needed
~ for the harvesting and conversion of the enough sunlight to displace all of the gasoline consumed in the United States

Challenges
~ the primary technical challenge is to lower costs of production in order to make BioHydrogen a commercially viable primary energy carrier
~ hydrogen production pathways in a variety of unicellular green algae, cyanobacteria, photosynthetic bacteria, and dark fermentative bacteria need to be optimized
~ a number of specific barriers to the cost effective production of BioHydrogen need to be overcome

~ bacteria Green algae and photosynthetic bacteria could operate with a solar energy conversion efficiency to H2
~ as high as ~10% and ~6%, respectively, provided that specific barriers are overcome