Start date: 05/01/00
End date: 09/30/02
About the research
The goal of this project was to develop an anaerobic fermentation process that converts negative-value organic wastes into hydrogen-rich gas that can significantly enhance the economic viability of many processes, either by utilizing hydrogen as a fuel source or as raw material for industries that consume hydrogen.
As a sustainable energy supply with minimal or zero use of hydrocarbons, hydrogen is a promising alternative to fossil fuel. It is a clean and environmentally friendly fuel that produces water instead of greenhouse gases when combusted. The waste streams from food processing plants such as corn, soybean, and meat plants pose a major burden on the environment. Aerobic wastewater treatment usually used for the treatment of these wastes requires energy input to provide aeration, whereas the anaerobic digestion process can achieve dual benefits of energy production in the form of hydrogen or methane and waste stabilization.
By using hardware that is similar to hardware used in industrial methane fermentation, the economics of hydrogen fermentation could be favorable due to its faster reaction rate. Additionally, hydrogen has a heating value of 61,100 Btu/lb, while methane has a heating value of 23,879 Btu/lb, nearly one third that of hydrogen. For global environmental considerations, production of hydrogen by biological reactions from renewable organic waste sources represents an important area of bioenergy production. Many investigations have been conducted using pure cultures of hydrogen-producing bacteria. Some of the studies showed promising results.
However, since wastewater is contaminated by bacteria, the purity of any wastewater treatment reactor is lost, and therefore the treatment of wastewater has to be a mixed culture process. Moreover, these studies were limited to the basic studies on microbial hydrogen metabolism. Their viability to real processes in terms of technical feasibility and commercialization potential has not been evaluated.
In this project, fundamental and practical feasibility studies of hydrogen fermentation from negative-value organic wastes were conducted using naturally available inocula (i.e., natural soil and compost) in continuous flow bioreactors. Various selection pressures were used to minimize contamination of the hydrogen-producing bacterial culture and avoid undesirable by-products. By selecting suitable waste streams and providing a favorable environment for the hydrogen-producers, relatively high conversion efficiencies will be maintained.
Nucleic acid-based techniques have the potential to provide detailed information on microbial population abundance and activity in complex environments, such as waste treatment systems. Techniques based on sequence analysis of ribosomal ribonucleic acid (rRNA) will be used to identify the microbial populations responsible for hydrogen production. Oligo nucleotide probes targeting the rRNA will be used to quantify the hydrogen-producing microorganisms and characterize the complex microbial community background. Later stages of the study will use pilot-scale reactors to demonstrate the effectiveness of real wastes in hydrogen production. Industries participating in this project used on-site demonstration units to produce hydrogen from their own wastewater. The cost efficiency of biohydrogen production was also evaluated.
Tech transfer summary: Slow Moving Vehicle Safety on Iowa's High-Speed Roadways (143 kb pdf) May 2009
- Ecofuel, Inc.
- U.S. Department of Energy