Updated: 11/24/2005; 11:23:17 PM.

Future energy
Renewables, fuel cells, hydrogen, and efficiency


daily link  Wednesday, June 01, 2005


Microbes produce hydrogen from waste:  Researchers: Hong Liu, postdoctoral researcher in environmental engineering; Stephen Grot, president and founder of Ion Power, Inc.; and Bruce Logan, Penn State professor of environmental engineering.  "Using a new electrically-assisted microbial fuel cell (MFC) that does not require oxygen, .. bacteria [produce] four times as much hydrogen directly out of biomass than can be generated typically by fermentation alone. ..

Bruce Logan says, "This MFC process is not limited to using only carbohydrate-based biomass for hydrogen production like conventional fermentation processes. We can theoretically use our MFC to obtain high yields of hydrogen from any biodegradable, dissolved, organic matter -- human, agricultural or industrial wastewater, for example -- and simultaneously clean the wastewater.  While there is likely insufficient waste biomass to sustain a global hydrogen economy, this form of renewable energy production may help offset the substantial costs of wastewater treatment as well as provide a contribution to nations able to harness hydrogen as an energy source." ..

hydrogen production by bacterial fermentation is currently limited by the "fermentation barrier" -- the fact that bacteria, without a power boost, can only convert carbohydrates to a limited amount of hydrogen and a mixture of "dead end" fermentation end products such as acetic and butyric acids.  However, giving the bacteria a small assist with a tiny amount of electricity -- about 0.25 volts or a small fraction of the voltage needed to run a typical 6 volt cell phone -- they can leap over the fermentation barrier and convert a "dead end" fermentation product, acetic acid, into carbon dioxide and hydrogen.  Logan notes, "Basically, we use the same microbial fuel cell we developed to clean wastewater and produce electricity. However, to produce hydrogen, we keep oxygen out of the MFC and add a small amount of power into the system." .. 

The researchers call their hydrogen-producing MFC a BioElectrochemically-Assisted Microbial Reactor or BEAMR. The BEAMR not only produces hydrogen but simultaneously cleans the wastewater used as its feedstock. It uses about one-tenth of the voltage needed for electrolysis, the process that uses electricity to break water down into hydrogen and oxygen. "  If this would work at a scale suitable for rural power cooperatives, it might prove useful to allow rural communities to become self-sufficient in fuel.  They have agricultural waste; their equipment and vehicles are relatively easy to convert even today to burn hydrogen; and the rural power systems often have small amounts of excess but hard to market electric power (eg, from wind or small hydro).

  11:59:07 PM  permalink  

 
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Copyright 2005 © Ken Novak.
Last update: 11/24/2005; 11:23:17 PM.