Environment

Researchers turn wastewater into “inexhaustible” source of hydrogen

Penn State researchers have developed an electrolysis cell with RED stack that produces pure hydrogen from waste water (Image: U.S. Fish & Wildlife Service)
Penn State researchers have developed an electrolysis cell with RED stack that produces pure hydrogen from waste water (Image: U.S. Fish & Wildlife Service)
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Bruce Logan's bacterial hydrolysis cell with reverse electrodialysis stack (Image: Bruce Logan, Penn State)
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Bruce Logan's bacterial hydrolysis cell with reverse electrodialysis stack (Image: Bruce Logan, Penn State)
An electrolysis cell with RED stack developed at Penn State produces pure hydrogen from waste water (Image: Logan, Penn State)
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An electrolysis cell with RED stack developed at Penn State produces pure hydrogen from waste water (Image: Logan, Penn State)
Penn State researchers have developed an electrolysis cell with RED stack that produces pure hydrogen from waste water (Image: U.S. Fish & Wildlife Service)
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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.

An electrolysis cell with RED stack developed at Penn State produces pure hydrogen from waste water (Image: Logan, Penn State)
An electrolysis cell with RED stack developed at Penn State produces pure hydrogen from waste water (Image: Logan, Penn State)

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."

29 comments
Patrick Luppi
Annoter step to true clean energy. Well done. P
pATREUS
So exciting!
jackmeister
I`m afraid I`m something of a cynic, I gotta feeling this will be the last time we see anything more about this.
mhenriday
Let us hope that this technique proves to be scalable and inexpensive, so that it can soon begin to be applied to the mountains of waste we produce.... Henri
Andrei Badescu
THIS IS GREAT! Funny part is that when I was a school boy (early sixties), I imagined such a system to produce a breathable oxygen/hydrogen to be used for scuba diving.. Of course, I had (and still have not) any idea if the mixture is breathable, but had concerns about having H2 and O together, thinking they might explode spontaneously... I had found out about \"concentration electric batteries\" from the French \"Science et Vie\"...
Mark Hutchinson
It seems jackmeister, that you were right. I couldn\'t find any mention of this in the Proceedings of the National Academy of Sciences publication (dated 19th September!). It\'s already gone! ???
oldbilbo
Interesting - long distance liveaboard, cruising or racing sailors could provide a stream of \'technology demonstrators\'. The organic waste produced by people living aboard a boat, plus the salt water environment would require just a little fresh water - stored or caught in rainfall/dew - as inputs. Less waste dumped in the seas, less fossil fuel consumed on the boats ( many thousands of these ) and hydrogen for power and light...? I\'d like to see it.
Alien
Interesting research and apparently with almost unimaginable potential. The questions that are not answered by this article are: (1) Is it scalable (2) How long is it likely to be before this technology could be applied on a commercial level? Incidentally, what is the relevance of Image No 3?
Renārs Grebežs
\"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.\" Does this mean that molybdenum sulfide makes just 51% of what platinum makes or is it something different altogether?
tkj
Breakthrough?? Doubtful that it will happen large-scale, cuz of my new \'Anderson\'s Rule\' : \"It takes 100+ alleged \'breakthroughs\' to have one real product come to market\"
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