Coupled Processes for BioEnergy Production: Biological Hydrogen Production Linked with Microbial Fuel Cells

PIs:
Jay Regan, Dept. of Civil and Environmental Engineering;
Bruce Logan , Dept. of Civil and Environmental Engineering;
Mark Guiltinan, Dept. of Horticulture

Funding: US Department of Agriculture, September 2003 - August 2006, $790,798.

Project Summary

For this project we are examining energy production from animal and farm wastes by producing hydrogen and electricity from these waste materials. Biological hydrogen production from a fermentation process will be economical only when the remaining chemicals from fermentation can be converted to another useful product. Microbial fuel cells (MFCs) offer great promise of a new technology to make that possible, while at the same time creating a new form of environmentally friendly energy production. MFCs offer the possibility for long-lived power generation utilizing diverse and abundant bio-fuels. MFCs utilize living catalysts that can regenerate and adapt to changing conditions, but work remains to increase their efficiency.

We will MFCs to biohydrogen production in a two-step process. In the first process, substrates will be fermented to produce hydrogen. We will investigate two biomass sources for this step: high cellulose, low lignin products; and animal wastes. For the first fermentation system, we will use metabolic engineering to adapt high hydrogen-producing bacteria to use cellulose. Clostridia bacteria are capable of degrading cellulose and hydrogen, but as yet there have been no reports of strains that accomplish both at high yields and rates. We have already developed bioreactor systems in our laboratory to produce gas streams of 60% hydrogen (40% CO2). We will use an approach to metabolically engineer bacteria capable of coupling hydrogen production with cellulose degradation. Hydrogen production from sugar-based substrates can reach 23 to 56% efficiency based on operation parameters such as detention time, temperature, and recycle. The second fermentation process we would examine is production of hydrogen from animal wastewater. Hydrogen can be recovered using our procedures to inoculate and maintain a hydrolysis/fermentation reactor of the type normally used as a first step in a two-step methane digestor system. The second step of our system, however, will not evolve methane but rather generate electricity directly.

In the second process, the products of the fermentation process (which are no longer capable of being converted to hydrogen) are converted directly into electricity in the MFC. Here, we would engineer a system to obtain electricity production from animal and farm wastewaters. We envision that we can recover 50% of the energy of this system in the form of hydrogen or electricity directly in this two-stage process. We will be aided in our research through our collaboration with researchers at NREL