Self-powered hydrogen generation from bacteria

catsmate1 · 20th September 2011, 12:45 PM

According to this interesting article in the US Proceedings of the National Academy of Sciences US researchers have managed to generate hydrogen by bacterial action without needing an external power source. If correct this is a major breakthrough in practical hydrogen fuel production, though currently cost is too great for commercial use.
There's a good article on the paper on the BBC website.

Originally Posted by Abstract

There is a tremendous source of entropic energy available from the salinity difference between river water and seawater, but this energy has yet to be efficiently captured and stored. Here we demonstrate that H2 can be produced in a single process by capturing the salinity driven energy along with organic matter degradation using exoelectrogenic bacteria. Only five pairs of seawater and river water cells were sandwiched between an anode, containing exoelectrogenic bacteria, and a cathode, forming a microbial reverse-electrodialysis electrolysis cell. Exoelectrogens added an electrical potential from acetate oxidation and reduced the anode overpotential, while the reverse electrodialysis stack contributed 0.5–0.6 V at a salinity ratio (seawater:river water) of 50. The H2 production rate increased from 0.8 to 1.6 m3-H2/m3-anolyte/day for seawater and river water flow rates ranging from 0.1 to 0.8 mL/ min. H2 recovery, the ratio of electrons used for H2 evolution to electrons released by substrate oxidation, ranged from 72% to 86%. Energy efficiencies, calculated from changes in salinities and the loss of organic matter, were 58% to 64%. By using a relatively small reverse electrodialysis stack (11 membranes), only ∼1% of the produced energy was needed for pumping water. Although Pt was used on the cathode in these tests, additional tests with a nonprecious metal catalyst (MoS2) demonstrated H2 production at a rate of 0.8 m3/m3/d and an energy efficiency of 51%. These results show that pure H2 gas can efficiently be produced from virtually limitless supplies of seawater and river water, and biodegradable organic matter.

Mikemcc · 20th September 2011, 10:58 PM

By not requiring an external power source they are meaning that they don't need to apply a current across the cells to generate the hydrogen. There will still be a requirement to run pumps, cultivate, and maintain the organisms, etc.

phildonnia · 20th September 2011, 11:34 PM

I didn't quite understand the sciencey bit. Where does the energy come from?

nvidiot · 21st September 2011, 12:10 AM

Iiiiiiinteresting.

I'm a bit confused as well, but the BBC link says:

Quote:

The MECs use something called "reverse electrodialysis" (RED), which refers to the energy gathered from the difference in salinity, or salt content, between saltwater and freshwater.

ETA: wiki link for MEC (Microbial Electrolysis Cell)

ETA2: A good diagram for the process is here on wiki too

Darat · 21st September 2011, 12:14 AM

Originally Posted by phildonnia

I didn't quite understand the sciencey bit. Where does the energy come from?

Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources?

bjornart · 21st September 2011, 01:08 AM

Originally Posted by phildonnia

I didn't quite understand the sciencey bit. Where does the energy come from?

From the quote in the OP:

Quote:

Here we demonstrate that H2 can be produced in a single process by capturing the salinity driven energy along with organic matter degradation using exoelectrogenic bacteria.

Salinity differences and stuff rotting.

catsmate1 · 21st September 2011, 02:14 AM

Originally Posted by Darat

Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources?

Yes there will be extraction/containment/cultivation energy costs. The process is analogous to fermentation of sugar to alcohols, provide feedstock and the micro-organisms will produce the hydrogen; the output gas will need to be pumped and compressed. With development the process should be cheaper than current methods for hydrogen production, steam reforming requires fossil fuels and heat and electrolysis is very energy intensive.
It's a start, not a solution.

Lukraak_Sisser · 21st September 2011, 02:59 AM

Originally Posted by Darat

Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources?

Part of it could I suppose be easily linked to a large freshwater pump system containing degredable organic matter present in all large cities (ie, the sewer system)
The sewage would provide the energy for the bacteria to grow and produce H2.
The salt water is harder. For seaside cities this could quite conceivably be a process with a net energy gain, but I suspect that pumping seawater any real distance negates such a gain.
Of course if treating sewage in seaside cities becomes an energy producer rather than consumer this would in the long run benefit any city hooked up to the same grid.

nvidiot · 21st September 2011, 03:20 AM

Wouldn't it be quite easy to make salt water in places that have none, by just adding salt to the fresh water? A lot easier than moving salt water around.

bjornart · 21st September 2011, 04:41 AM

Originally Posted by nvidiot

Wouldn't it be quite easy to make salt water in places that have none, by just adding salt to the fresh water? A lot easier than moving salt water around.

Salt may be cheap, but I doubt it's so cheap that would make sense.

BenBurch · 21st September 2011, 06:03 AM

Bacteria don't just live on nothing. They need an energy source. For most bacteria this is chemical energy derived from their environment. For photosynthetic or radiosynthetic bacteria, an external energy source is captured and converted into chemical energy for the cell to use.

Nothing here has shown what they eat.

richardm · 21st September 2011, 06:39 AM

Originally Posted by BenBurch

Nothing here has shown what they eat.

It's bacteria all the way down.

nvidiot · 21st September 2011, 06:45 AM

Quote:

Bacteria don't just live on nothing. They need an energy source. For most bacteria this is chemical energy derived from their environment. For photosynthetic or radiosynthetic bacteria, an external energy source is captured and converted into chemical energy for the cell to use.

Nothing here has shown what they eat.

Of course they don't live on nothing Ben, the paper apparently suggests wastewater as the organic material source. The BBC link in the OP has a quote from the authors.

Cuddles · 21st September 2011, 07:21 AM

Originally Posted by phildonnia

I didn't quite understand the sciencey bit. Where does the energy come from?

http://en.wikipedia.org/wiki/Reverse_electrodialysis

Basically, when you dissolve something in water, energy is either used or released. So when you put two volumes of water with different concentration next to each other you get an energy gradient, and like any gradient it can be exploited to do work, at least in theory. It's essentially the same principle as two different metals producing a voltage when put together.

From the Wiki article, it appears this principle is already being looked into as a means of producing electricity. This new research is instead looking at using it to produce hydrogen directly, without the inefficiencies that would be present from first making electricity and then using that for electrolysis. The main question is likely to be how efficient this method actually is, and whether it would actually be better than just producing electricity without the bacteria getting involved.

Cainkane1 · 21st September 2011, 07:36 AM

What the world needs is a lot of cheap power. This is very interesting but can we put this to use on a large scale and can the ordinary citizen afford it?

bjornart · 21st September 2011, 08:04 AM

Originally Posted by Cainkane1

What the world needs is a lot of cheap power. This is very interesting but can we put this to use on a large scale and can the ordinary citizen afford it?

We won't know until we try.

phildonnia · 21st September 2011, 04:34 PM

Originally Posted by Cuddles

http://en.wikipedia.org/wiki/Reverse_electrodialysis

Ok, so basically, fresh water has higher potential than salt water?

BenBurch · 22nd September 2011, 06:06 AM

Originally Posted by nvidiot

Of course they don't live on nothing Ben, the paper apparently suggests wastewater as the organic material source. The BBC link in the OP has a quote from the authors.

Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses.

dlorde · 22nd September 2011, 08:18 AM

Originally Posted by Darat

Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources?

There's a partial answer in the quoted abstract:

Quote:

By using a relatively small reverse electrodialysis stack (11 membranes), only ∼1% of the produced energy was needed for pumping water.

Cuddles · 22nd September 2011, 08:30 AM

Originally Posted by phildonnia

Ok, so basically, fresh water has higher potential than salt water?

Pretty much. It's the same basic principle as putting salt on a slug to kill it, or why salt and sugar work as preservatives - water will tend to flow through a membrane from high concentration to low concentration, even when there are other pressures trying to stop it. The slug keeps its water inside just fine, but put salt on it and the osmotic pressure is enough to suck it out. The same sucking can be harnessed to produce electricity or, in this case, to directly produce hydrogen, or in other ways such as simply acting as a water pump.

phildonnia · 22nd September 2011, 08:51 AM

Ok, so it ultimately runs on fresh water. Glad to hear we have an energy supply that uses an inexhaustible, infinite source.

Buckaroo · 22nd September 2011, 09:12 AM

Cool. During my days at the NSF back in 2004 I was involved in a similar story, also with Bruce Logan as an investigator: http://www.nsf.gov/news/news_summ.jsp?cntn_id=100337

nvidiot · 22nd September 2011, 03:04 PM

Originally Posted by phildonnia

Ok, so it ultimately runs on fresh water. Glad to hear we have an energy supply that uses an inexhaustible, infinite source.

There is substantial amounts of energy available in salinity gradients, the trick is how to liberate it. This appears to be a substantial improvement in efficiency, which will likely spur more investment and development, and hopefully more efficiency and so on.

Quote:

BenBurch

Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses.

City sewages wouldn't be the only domestic source, farm wastes, household organic wastes, heck all kinds of organic material is wasted by human civilisation and would be relatively easy to recover if sufficiently valued. I'm sure they'll expand potential biological agents using all kinds of neat byproducts as nutrient sources. Genetic engineering could provide some novel solutions too.

This is not the solution to our energy issues, and won't be for decades even if it can be appropriately scaled for large loads. That said, we could be looking at a large and untapped energy source and given the situation humanity finds itself in, it would be quite wise to invest in such ideas.

phildonnia · 23rd September 2011, 12:19 AM

Originally Posted by nvidiot

There is substantial amounts of energy available in salinity gradients, the trick is how to liberate it. This appears to be a substantial improvement in efficiency, which will likely spur more investment and development, and hopefully more efficiency and so on.

Don't get me wrong; I'm glad to hear that there is another source of energy that we can add to the mix in the future. We should be cautious not to assume that the magic bullet for our increasing energy demands has been found.

CORed · 23rd September 2011, 10:10 AM

Originally Posted by BenBurch

Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses.

A lot of sewage plants capture methane produced by anaerobic digesters and use it to power generators. In most cases, I don't believe this produces as much energy as the sewage plant uses.

aggle-rithm · 23rd September 2011, 10:13 AM

I, for one, welcome our new hydrogen-producing bacteria overlords.

20th September 2011, 12:45 PM	#1
catsmate1 Philosopher Join Date: Apr 2007 Location: Dublin (the one in Ireland) Posts: 7,140	Self-powered hydrogen generation from bacteria According to this interesting article in the US Proceedings of the National Academy of Sciences US researchers have managed to generate hydrogen by bacterial action without needing an external power source. If correct this is a major breakthrough in practical hydrogen fuel production, though currently cost is too great for commercial use. There's a good article on the paper on the BBC website. Originally Posted by Abstract There is a tremendous source of entropic energy available from the salinity difference between river water and seawater, but this energy has yet to be efficiently captured and stored. Here we demonstrate that H2 can be produced in a single process by capturing the salinity driven energy along with organic matter degradation using exoelectrogenic bacteria. Only five pairs of seawater and river water cells were sandwiched between an anode, containing exoelectrogenic bacteria, and a cathode, forming a microbial reverse-electrodialysis electrolysis cell. Exoelectrogens added an electrical potential from acetate oxidation and reduced the anode overpotential, while the reverse electrodialysis stack contributed 0.5–0.6 V at a salinity ratio (seawater:river water) of 50. The H2 production rate increased from 0.8 to 1.6 m3-H2/m3-anolyte/day for seawater and river water flow rates ranging from 0.1 to 0.8 mL/ min. H2 recovery, the ratio of electrons used for H2 evolution to electrons released by substrate oxidation, ranged from 72% to 86%. Energy efficiencies, calculated from changes in salinities and the loss of organic matter, were 58% to 64%. By using a relatively small reverse electrodialysis stack (11 membranes), only ∼1% of the produced energy was needed for pumping water. Although Pt was used on the cathode in these tests, additional tests with a nonprecious metal catalyst (MoS2) demonstrated H2 production at a rate of 0.8 m3/m3/d and an energy efficiency of 51%. These results show that pure H2 gas can efficiently be produced from virtually limitless supplies of seawater and river water, and biodegradable organic matter.

20th September 2011, 10:58 PM	#2
Mikemcc Muse Join Date: Dec 2009 Posts: 958	By not requiring an external power source they are meaning that they don't need to apply a current across the cells to generate the hydrogen. There will still be a requirement to run pumps, cultivate, and maintain the organisms, etc.
Mikemcc Muse Join Date: Dec 2009 Posts: 958

21st September 2011, 12:10 AM	#4
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	Iiiiiiinteresting. I'm a bit confused as well, but the BBC link says: Quote: The MECs use something called "reverse electrodialysis" (RED), which refers to the energy gathered from the difference in salinity, or salt content, between saltwater and freshwater. ETA: wiki link for MEC (Microbial Electrolysis Cell) ETA2: A good diagram for the process is here on wiki too
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	__________________ www.horsemen-gaming.com Last edited by nvidiot; 21st September 2011 at 12:14 AM.

21st September 2011, 12:14 AM	#5
Darat Lackey Administrator / JREF Forum Liaison Join Date: Aug 2001 Location: South East, UK Posts: 64,804	Originally Posted by phildonnia I didn't quite understand the sciencey bit. Where does the energy come from? Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources?
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21st September 2011, 01:08 AM	#6
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	Originally Posted by phildonnia I didn't quite understand the sciencey bit. Where does the energy come from? From the quote in the OP: Quote: Here we demonstrate that H2 can be produced in a single process by capturing the salinity driven energy along with organic matter degradation using exoelectrogenic bacteria. Salinity differences and stuff rotting.
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	__________________ Well, I DON'T CARE WHAT YOU LIKE TO BELIEVE, GODDAMMIT! I DEAL IN THE FACTS! -Cecil Adams

20th September 2011, 11:34 PM	#3
phildonnia Master Poster Join Date: Oct 2001 Location: Sac'to CA Posts: 2,339	I didn't quite understand the sciencey bit. Where does the energy come from?

21st September 2011, 02:14 AM	#7
catsmate1 Philosopher Join Date: Apr 2007 Location: Dublin (the one in Ireland) Posts: 7,140	Originally Posted by Darat Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources? Yes there will be extraction/containment/cultivation energy costs. The process is analogous to fermentation of sugar to alcohols, provide feedstock and the micro-organisms will produce the hydrogen; the output gas will need to be pumped and compressed. With development the process should be cheaper than current methods for hydrogen production, steam reforming requires fossil fuels and heat and electrolysis is very energy intensive. It's a start, not a solution.

21st September 2011, 02:59 AM	#8
Lukraak_Sisser Graduate Poster Join Date: Aug 2009 Posts: 1,623	Originally Posted by Darat Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources? Part of it could I suppose be easily linked to a large freshwater pump system containing degredable organic matter present in all large cities (ie, the sewer system) The sewage would provide the energy for the bacteria to grow and produce H2. The salt water is harder. For seaside cities this could quite conceivably be a process with a net energy gain, but I suspect that pumping seawater any real distance negates such a gain. Of course if treating sewage in seaside cities becomes an energy producer rather than consumer this would in the long run benefit any city hooked up to the same grid.

21st September 2011, 03:20 AM	#9
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	Wouldn't it be quite easy to make salt water in places that have none, by just adding salt to the fresh water? A lot easier than moving salt water around.
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	__________________ www.horsemen-gaming.com

21st September 2011, 04:41 AM	#10
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	Originally Posted by nvidiot Wouldn't it be quite easy to make salt water in places that have none, by just adding salt to the fresh water? A lot easier than moving salt water around. Salt may be cheap, but I doubt it's so cheap that would make sense.
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	__________________ Well, I DON'T CARE WHAT YOU LIKE TO BELIEVE, GODDAMMIT! I DEAL IN THE FACTS! -Cecil Adams

21st September 2011, 06:03 AM	#11
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,222	Bacteria don't just live on nothing. They need an energy source. For most bacteria this is chemical energy derived from their environment. For photosynthetic or radiosynthetic bacteria, an external energy source is captured and converted into chemical energy for the cell to use. Nothing here has shown what they eat.
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21st September 2011, 06:39 AM	#12
richardm Philosopher Join Date: Aug 2001 Posts: 9,270	Originally Posted by BenBurch Nothing here has shown what they eat. It's bacteria all the way down.
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21st September 2011, 06:45 AM	#13
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	Quote: Bacteria don't just live on nothing. They need an energy source. For most bacteria this is chemical energy derived from their environment. For photosynthetic or radiosynthetic bacteria, an external energy source is captured and converted into chemical energy for the cell to use. Nothing here has shown what they eat. Of course they don't live on nothing Ben, the paper apparently suggests wastewater as the organic material source. The BBC link in the OP has a quote from the authors.
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21st September 2011, 07:21 AM	#14
Cuddles Decoy Moderator Join Date: Jul 2006 Location: A magical land full of pink fluffy sheeps and bunnies Posts: 16,597	Originally Posted by phildonnia I didn't quite understand the sciencey bit. Where does the energy come from? http://en.wikipedia.org/wiki/Reverse_electrodialysis Basically, when you dissolve something in water, energy is either used or released. So when you put two volumes of water with different concentration next to each other you get an energy gradient, and like any gradient it can be exploited to do work, at least in theory. It's essentially the same principle as two different metals producing a voltage when put together. From the Wiki article, it appears this principle is already being looked into as a means of producing electricity. This new research is instead looking at using it to produce hydrogen directly, without the inefficiencies that would be present from first making electricity and then using that for electrolysis. The main question is likely to be how efficient this method actually is, and whether it would actually be better than just producing electricity without the bacteria getting involved.
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21st September 2011, 07:36 AM	#15
Cainkane1 Philosopher Join Date: Jul 2005 Location: The great American southeast Posts: 7,198	What the world needs is a lot of cheap power. This is very interesting but can we put this to use on a large scale and can the ordinary citizen afford it?
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21st September 2011, 08:04 AM	#16
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	Originally Posted by Cainkane1 What the world needs is a lot of cheap power. This is very interesting but can we put this to use on a large scale and can the ordinary citizen afford it? We won't know until we try.
bjornart Master Poster Join Date: Nov 2002 Posts: 2,398	__________________ Well, I DON'T CARE WHAT YOU LIKE TO BELIEVE, GODDAMMIT! I DEAL IN THE FACTS! -Cecil Adams

21st September 2011, 04:34 PM	#17
phildonnia Master Poster Join Date: Oct 2001 Location: Sac'to CA Posts: 2,339	Originally Posted by Cuddles http://en.wikipedia.org/wiki/Reverse_electrodialysis Ok, so basically, fresh water has higher potential than salt water?

22nd September 2011, 06:06 AM	#18
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,222	Originally Posted by nvidiot Of course they don't live on nothing Ben, the paper apparently suggests wastewater as the organic material source. The BBC link in the OP has a quote from the authors. Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses.
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22nd September 2011, 08:18 AM	#19
dlorde Illuminator Join Date: Apr 2007 Posts: 4,647	Originally Posted by Darat Yeah - come on big brains explain to us where the magic comes from! Also as others have mentioned there would be be energy inputs into such a system such as the pumps and so on - is it likely that the net output would be positive when those energy costs are taken into account or is this one that would still rely on being manufactured using non-renewable energy sources? There's a partial answer in the quoted abstract: Quote: By using a relatively small reverse electrodialysis stack (11 membranes), only ∼1% of the produced energy was needed for pumping water.
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22nd September 2011, 08:30 AM	#20
Cuddles Decoy Moderator Join Date: Jul 2006 Location: A magical land full of pink fluffy sheeps and bunnies Posts: 16,597	Originally Posted by phildonnia Ok, so basically, fresh water has higher potential than salt water? Pretty much. It's the same basic principle as putting salt on a slug to kill it, or why salt and sugar work as preservatives - water will tend to flow through a membrane from high concentration to low concentration, even when there are other pressures trying to stop it. The slug keeps its water inside just fine, but put salt on it and the osmotic pressure is enough to suck it out. The same sucking can be harnessed to produce electricity or, in this case, to directly produce hydrogen, or in other ways such as simply acting as a water pump.
	__________________ I am not a little teapot.

22nd September 2011, 08:51 AM	#21
phildonnia Master Poster Join Date: Oct 2001 Location: Sac'to CA Posts: 2,339	Ok, so it ultimately runs on fresh water. Glad to hear we have an energy supply that uses an inexhaustible, infinite source.

22nd September 2011, 09:12 AM	#22
Buckaroo Graduate Poster Join Date: Feb 2006 Location: Washington, D.C. Posts: 1,718	Cool. During my days at the NSF back in 2004 I was involved in a similar story, also with Bruce Logan as an investigator: http://www.nsf.gov/news/news_summ.jsp?cntn_id=100337
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22nd September 2011, 03:04 PM	#23
nvidiot Botanical Jedi Join Date: Apr 2010 Posts: 1,793	Originally Posted by phildonnia Ok, so it ultimately runs on fresh water. Glad to hear we have an energy supply that uses an inexhaustible, infinite source. There is substantial amounts of energy available in salinity gradients, the trick is how to liberate it. This appears to be a substantial improvement in efficiency, which will likely spur more investment and development, and hopefully more efficiency and so on. Quote: BenBurch Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses. City sewages wouldn't be the only domestic source, farm wastes, household organic wastes, heck all kinds of organic material is wasted by human civilisation and would be relatively easy to recover if sufficiently valued. I'm sure they'll expand potential biological agents using all kinds of neat byproducts as nutrient sources. Genetic engineering could provide some novel solutions too. This is not the solution to our energy issues, and won't be for decades even if it can be appropriately scaled for large loads. That said, we could be looking at a large and untapped energy source and given the situation humanity finds itself in, it would be quite wise to invest in such ideas.
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23rd September 2011, 12:19 AM	#24
phildonnia Master Poster Join Date: Oct 2001 Location: Sac'to CA Posts: 2,339	Originally Posted by nvidiot There is substantial amounts of energy available in salinity gradients, the trick is how to liberate it. This appears to be a substantial improvement in efficiency, which will likely spur more investment and development, and hopefully more efficiency and so on. Don't get me wrong; I'm glad to hear that there is another source of energy that we can add to the mix in the future. We should be cautious not to assume that the magic bullet for our increasing energy demands has been found.

23rd September 2011, 10:10 AM	#25
CORed Illuminator Join Date: Dec 2008 Posts: 4,295	Originally Posted by BenBurch Ah, OK. That is a very limited resource, believe it or not. You might think that well, there is a lot of crap in the world, but when you look at the energy content of a city's sewage, it does not amount to much in terms of the energy the city uses. A lot of sewage plants capture methane produced by anaerobic digesters and use it to power generators. In most cases, I don't believe this produces as much energy as the sewage plant uses.
CORed Illuminator Join Date: Dec 2008 Posts: 4,295

23rd September 2011, 10:13 AM	#26
aggle-rithm Ardent Formulist Join Date: Jun 2005 Location: Austin, TX Posts: 14,156	I, for one, welcome our new hydrogen-producing bacteria overlords.
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