Investigators: Bruce E. Logan, Penn State University; Dr. Greg Bowden, USFilter Corp.

The conversion of organic matter directly to CO2 by aerobic wastewater treatment processes is efficient at removing the carbonaceous oxygen demand of these waste streams, but this approach wastes a valuable resource—hydrogen gas.  Anaerobic conversion of organic matter into hydrogen could reduce costs for aeration at treatment plants, and generate electricity from hydrogen gas using fuel cell technology. The complete conversion of organic matter in wastewater (C₁₀H₁₉O₃N) to hydrogen and carbon dioxide could potentially produce 32.5 moles of H₂. In practice, such yields are limited by biochemical routes. For example, the maximum yield for glucose is 4 mol H₂/mole-glucose.

H₂ production by acetogenic microbes has been claimed to be a thermodynamically unfavorable process sensitive to accumulation of H2 in the micromolar range. However, this is not always true, and we have recently shown that it is possible to obtain very high concentrations of hydrogen gas (50 to 70%) with yields approaching 50% (based on conversion to acetate and hydrogen). While all of the organic matter in a wastewater stream cannot be converted to H2, there is enormous potential of producing hydrogen from wastewater.

We are working with US Filter to devise a bioreactor for producing hydrogen gas from industrial wastewaters.  Bench scale tests are being conducted to measure hydrogen production from various wastewaters and to optimize the conversion efficiency of organic matter in continuous flow reactors.