Tuesday, September 27, 2011

Hydrogen From Wastewater Protocol




This is definitely a different twist on the challenge of producing energy.  I do not see though how this could easily be engineered into a practical system actually able to pay for itself.  Yet we may have a valuable process whose natural byproduct happens to be plentiful hydrogen.  If that can be made true then this could go somewhere.

Many processes succeed in the lab but never go further because the engineering challenge itself is either insurmountable or too expensive. This one remains to be seen and it is early days.

However it does provide a viable route to hydrogen production that does not begin by costing way more energy than it makes available.  We really have not had that before or at least something easy enough to work with.

Researchers turn wastewater into “inexhaustible” source of hydrogen

23:25 September 19, 2011


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Penn State researchers have developed an electrolysis cell with RED stack that produces pure hydrogen from waste water (Image: U.S. Fish & Wildlife Service)

Currently, the world economy and western society in general runs on fossil fuels. We've known for some time that this reliance on finite resources that are polluting the planet is unsustainable in the long term. This has led to the search for alternatives and hydrogen is one of the leading contenders. One of the problems is that hydrogen is an energy carrier, rather than an energy source. Pure hydrogen doesn't occur naturally and it takes energy - usually generated by fossil fuels - to manufacture it. Now researchers at Pennsylvania State University have developed a way to produce hydrogen that uses no grid electricity and is carbon neutral and could be used anyplace that there is wastewater near sea water.

The researchers' work revolves around microbial electrolysis cells (MECs) - a technology related to microbial fuel cells (MFCs), which produce an electric current from the microbial decomposition of organic compounds. MECs partially reverse this process to generate hydrogen (or methane) from organic material but they require the some electrical input to do so.

Instead of relying on the grid to provide the electricity required for their MECs, Bruce E. Logan, Kappe Professor of Environmental Engineering, and postdoctoral fellow Younggy Kim, turned to reverse-electrodialysis (RED). We've previously looked at efforts to use RED to generate electricity using salt water from the North Sea and fresh water from the Rhine and the Penn State team's work follows the same principle - extracting energy from the ionic differences between salt water and fresh water.

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A RED stack consists of alternating positive and negative ion exchange membranes, with each RED contributing additively to the electrical output. Logan says that using RED stacks to generate electricity has been proposed before but, because they are trying to drive an unfavorable reaction, many membrane pairs are required. To split water into hydrogen and oxygen using RED technology requires 1.8 volts, which would require about 25 pairs of membranes, resulting in increased pumping resistance.

But by combining RED technology with exoelectrogenic bacteria - bacteria that consume organic material and produce an electric current - the researchers were able to reduce the number of RED stacks required to five membrane pairs.

Previous work with MECs showed that, by themselves, they could produce about 0.3 volts of electricity, but not the 0.414 volts needed to generate hydrogen in these fuel cells. Adding less than 0.2 volts of outside electricity released the hydrogen. Now, by incorporating 11 membranes - five membrane pairs that produce about 0.5 volts - the cells produce hydrogen.

"The added voltage that we need is a lot less than the 1.8 volts necessary to hydrolyze water," said Logan. "Biodegradable liquids and cellulose waste are abundant and with no energy in and hydrogen out we can get rid of wastewater and by-products. This could be an inexhaustible source of energy."

While Logan and Kim used platinum as the catalyst on the cathode in their initial experiments, subsequent experimentation showed that a non-precious metal catalyst, molybdenum sulfide, had 51 percent energy efficiency.

The Penn State researchers say their results, which are published in the Sept. 19 issue of the Proceedings of the National Academy of Sciences, "show that pure hydrogen gas can efficiently be produced from virtually limitless supplies of seawater and river water and biodegradable organic matter."


'Inexhaustible' Source of Hydrogen May Be Unlocked by Salt Water, Engineers Say


ScienceDaily (Sep. 19, 2011) — A grain of salt or two may be all that microbial electrolysis cells need to produce hydrogen from wastewater or organic byproducts, without adding carbon dioxide to the atmosphere or using grid electricity, according to Penn State engineers.

"This system could produce hydrogen anyplace that there is wastewater near sea water," said Bruce E. Logan, Kappe Professor of Environmental Engineering. "It uses no grid electricity and is completely carbon neutral. It is an inexhaustible source of energy."

Microbial electrolysis cells that produce hydrogen are the basis of this recent work, but previously, to produce hydrogen, the fuel cells required some electrical input. Now, Logan, working with postdoctoral fellow Younggy Kim is using the difference between river water and seawater to add the extra energy needed to produce hydrogen.

Their results, published Sept. 19 in the Proceedings of the National Academy of Sciences, "show that pure hydrogen gas can efficiently be produced from virtually limitless supplies of seawater and river water and biodegradable organic matter."

Logan's cells were between 58 and 64 percent efficient and produced between 0.8 to 1.6 cubic meters of hydrogen for every cubic meter of liquid through the cell each day. The researchers estimated that only about 1 percent of the energy produced in the cell was needed to pump water through the system.

The key to these microbial electrolysis cells is reverse-electrodialysis or RED that extracts energy from the ionic differences between salt water and fresh water. A RED stack consists of alternating ion exchange membranes -- positive and negative -- with each RED contributing additively to the electrical output.

"People have proposed making electricity out of RED stacks," said Logan. "But you need so many membrane pairs and are trying to drive an unfavorable reaction."

For RED technology to hydrolyze water -- split it into hydrogen and oxygen -- requires 1.8 volts, which would in practice require about 25 pairs of membrane sand increase pumping resistance. However, combining RED technology with exoelectrogenic bacteria -- bacteria that consume organic material and produce an electric current -- reduced the number of RED stacks to five membrane pairs.

Previous work with microbial electrolysis cells showed that they could, by themselves, produce about 0.3 volts of electricity, but not the 0.414 volts needed to generate hydrogen in these fuel cells. Adding less than 0.2 volts of outside electricity released the hydrogen. Now, by incorporating 11 membranes -- five membrane pairs that produce about 0.5 volts -- the cells produce hydrogen.

"The added voltage that we need is a lot less than the 1.8 volts necessary to hydrolyze water," said Logan. "Biodegradable liquids and cellulose waste are abundant and with no energy in and hydrogen out we can get rid of wastewater and by-products. This could be an inexhaustible source of energy."

Logan and Kim's research used platinum as a catalyst on the cathode, but subsequent experimentation showed that a non-precious metal catalyst, molybdenum sulfide, had a 51 percent energy efficiency. The King Abdullah University of Science and 

1 comment:

Amela Jones said...

Is there any further reading you would recommend on this?

Amela
Waste Water Services

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