Background: The production of H2 gas via biological production has many attractive advantages as compared to other methods of energy production. It is renewable does not release CO2 through combustion produces large amounts of energy and is easily converted to electricity by fuel cells. The direct production of electricity by microbes in fuel cells also possesses these same advantages. In order to fully realize the potential of biological-mediated energy production technologies need to be integrated that increase the efficiency and ensure the long-term productivity of such devices. Technology: Researchers at the University of Iowa have engineered a device that consists of several layers of a thin porous material which serves as a substrate for the growth of microbes that produce energy through the conversion of organic waste materials. The purpose of this device is to allow the microbes on each layer to capture as much light as possible while allowing the unused light to filter down to the levels below. The microbes selected for each layer of the apparatus may be optimized for the most efficient level of energy production be it either H2 or electricity. There are several energy-producing biologicals that can be included in this system which include but is not limited to any combination of algae Rhodopseudomonas plaustris Escherichia coli Shewanella putrifaciens Clostridium butyricum Chlamydomonas species Rubrivivax species Rhodobacter species Rhodococcus species and Geobaster species.
(1) Increased Efficiency: The composite biological device incorporates a layered structure allowing for efficient use of light through an orderly arrangment of microbes requiring high- to low-light conditions for optimal production. (2) Opportunity for Microbe Optimization: Several biological component options are available including several wild type and mutated microbes. (3) Amenable to gas or electricity production: This technology can be used for production of H2 for conversion in a fuel cell or for direct production of electricity depending on the microbes selected as the biological component.