Researchers Develop Two-stage Bioreactor System for Optimized Bio-Hydrogen Production
17 July 2008
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| The process flow of the two-stage bio-hydrogen system. Click to enlarge. Source: biowaste2energy. |
Researchers at the University of Birmingham (UK) have combined two types of hydrogen-producing bacteria—one that uses fermentation, and the other that uses photosynthesis—in a two-stage bioreactor system to produce hydrogen from sugary feedstocks.
According to an article describing the process in the August issue of Microbiology Today, this technology has an added bonus: leftover enzymes can be used to scavenge precious metals from spent automotive catalysts to help make fuel cells that convert hydrogen into energy.
There are special and yet prevalent circumstances under which micro-organisms have no better way of gaining energy than to release hydrogen into their environment. Microbes such as heterotrophs, cyanobacteria, microalgae and purple bacteria all produce biohydrogen in different ways.
—Dr. Mark Redwood, University of Birmingham
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| Biohydrogenic microorganisms. Click to enlarge. Source: Redwood and Mackaskie (2008). |
When there is no oxygen, fermentative bacteria use carbohydrates like sugar to produce hydrogen and acids. Others, like purple bacteria, use light to produce energy (photosynthesis) and make hydrogen to help them break down molecules such as acids. These two reactions fit together as the purple bacteria can use the acids produced by the fermentation bacteria.
These two bioreactions fit together as the organic acid products of dark fermentation represent the ideal substrates for purple bacteria. When assembled in the laboratory, the bioprocess represents an everyday process occurring in nature where the two types of bacteria co-exist, but in the bioprocess the two bioreactors are optimized to provide the ideal conditions for H2 production by the two different mechanisms.
—Redwood and Macaskie (2008)
Professor Lynne Macaskie’s Unit of Functional Bionanomaterials at the University of Birmingham has created a bioreactor that combines the two-stage fermentation process with patented novel membrane technology with permits economically viable yields of hydrogen from feedstocks such as food wastes.
Biodegradable waste is pretreated to remove or degrade inert materials and to convert semi-inert materials into readily biodegradable substrates. This is then is supplied to a bioreactor containing fermentative bacteria, which rapidly consume sugary substrates to produce hydrogen and a mixture of organic products including acetic acid.
The membrane technology removes the organic products, which would otherwise accumulate and inhibit hydrogen production. Simultaneously, a concentrated product stream is generated, which is ideal for conversion to additional hydrogen by photosynthetic bacteria in the second reactor, a photobioreactor, specially adapted to harvest solar energy.
The maximum quantity of H2 that could be potentially recovered from sugary feedstocks is 12 mol H2 per mol hexose unit, but this kind of efficiency cannot be approached by a single organism. The dual bioreactor process can approach this maximum by producing up to 4 mol H2 in the dark reactor and up to 8 mol H2 in the photobioreactor.
—Redwood and Macaskie (2008)
With a more advanced pre-treatment, biohydrogen can be produced from the waste from food-crop cultivation, such as corn stalks and husks.
The University of Birmingham has teamed up with Modern Waste Ltd and EKB Technology Ltd to form Biowaste2energy Ltd, which will develop and commercialize this waste to energy technology.
In a final twist, the hydrogenase enzymes in the leftover bacteria can be used to scavenge precious metals from spent automotive catalysts to help make fuel cell that converts hydrogen into electricity. So nothing is wasted and an important new application can be found for today’s waste mountain in tomorrow’s non-fossil fuel transport and energy
— Professor Lynne Macaskie
Resources
Mark Redwood and Lynne Macaskie (2008) Life’s a gas... and it’s hydrogen, Microbiology Today, August 2008
Very cool. Capture the CO2, sequester it, and you have a carbon-negative fuel that removes CO2 from the atmosphere. The more you use your car powered by such a carbon-negative fuel, the more you fight global warming.
Posted by: Jonas | 17 July 2008 at 08:12 AM
With starving people eating mud in countries near the US, the question what are food wastes becomes important. Electricity is a more efficient energy carrier than hydrogen. ..HG..
Posted by: Henry Gibson | 17 July 2008 at 08:58 AM
lol.. you people are too much!
Now we can't use hydrogen because people are eating mud.
The question is what are you eating with your head lodged that far up your @ss
Posted by: Jim | 17 July 2008 at 09:39 AM
Hungry countries would want to give leaves, stalks and garbage to animals like pigs, goats and cattle. It would make no sense for developed countries to ship their crop and food wastes overseas, so the only issue is whether failing to feed this matter to animals in developed areas causes a shift in demand for animal protein to sources in the hungry countries.
Posted by: Reality Czech | 17 July 2008 at 09:42 AM
Given that most hungry countries are that way because of political mismanagement, I fail to see how hydrogen production will have a meaningful impact on the problem one way or another.
Posted by: Matthew | 17 July 2008 at 09:55 AM
There is nothing new in this research. Yes, microorganisms can be used to produce H2; but why would you do that?
From an energy standpoint, methane is the preferred output because it is much more energetic and easy to handle fuel. Second, the most beneficial product of using microorganisms to break down organic waste is organic fertilizer not producing energy. Such systems should be organized to maximize organic fertilizer to reduce the amount of energy it takes to make synthetic ammonia.
From a research standpoint, producing hydrogen is much better for getting grants. A picture of the shuttle blasting off is more interesting than pictures of compost piles or WWTPs.
Posted by: Kit P | 17 July 2008 at 10:29 AM
KitP:
the shuttle uses two SRBs fueled with ammonium perchlorate and aluminum and the main rocket engine which burns LOX/LH2 6:1 oxygen.
There is nothing wrong with using these processes to produce H2 which is a reasonably good energy carrier. That we can also make organic fertilizer is another good end to these processes. But one does not exclude the other. Both are viable in our energy future and the resultant dichotomy of land and technology will benefit greatly.
Posted by: gr | 17 July 2008 at 11:05 AM
@gr
You may want to send an email to the authors of of the study who posted a picture of shuttle informing them of their mistake.
However, there is something wrong with H2 as energy carrier. It is a very bad energy carrier especially compared to methane.
If you can find something in the “Life’s a gas... and it’s hydrogen, Microbiology Today, August 2008” that justifies it over production of methane, let me know. Can I assume you did not bother to read the study before taking issue with my critique?
Posted by: Kit P | 17 July 2008 at 04:28 PM
Didn't really take issue Kit, just confirmed that microbial H2 will become one of many H2 sources. Methane is good for some things though current SOFCs appear to be stuck at $4k/kWh - ten times what DOE has targeted. My main point is there are viable uses for a wide diversity of energy solutions.
Posted by: gr | 17 July 2008 at 11:48 PM
The cost of running biogas through a efficient ICE is about $1k/kWh. While fuel cells themselves are more efficient, invariable the efficiencies of producing the H2 offset any gain.
Again, this is not new. I have read many technical papers producing H2 and they all fail to provide a answer the question, why would you do it.
Here is the answer, You are getting a big grant and you do not care if it fails.
So gr you are wrong when you state, “just confirmed that microbial H2 will become one of many H2 sources.” It is a thermodynamic thing that does not require rocket science just simple (if you are a civil/environmental ) mass and energy balance. Again, read the study does it tell you how much of the VS (volatile solids) is converted to H2 compared to CH4 in a conventional AD and how much N goes out the vent as N2 and how much is available as organic fertilizer.
This is all somewhat counter intuitive gr. So let me ask you if you are interested in environmental solutions or energy solutions? In decreasing order of environmental benefit this is how waste should processed:
Conservation (do not create the waste in the first place)
Reuse
Recycle (turn it into a beneficial product like organic fertilizer or wall board)
Convert it too energy
So in general, the last thing you want to do with waste (before treating by using energy) is convert it energy and the last thing you want to do with energy is convert it to H2.
So gr let me ask how you normally get from the top floor of a building, do you use the stairs or do you use a parachute? Only boneheads who think H2 is a good energy carrier. The best way to demonstrate this to boneheads is with a baseball bat. While a baseball bat is not nearly as efficient as H2 at administering blunt force trauma, it is more visual.
Posted by: Kit P | 18 July 2008 at 08:00 AM
Kit, you might consider watching an hilarious motion picture called "Anger Management." It is wildly entertaining! BTW, I used to work in the Empire State Building and there, neither the stairs nor parachute were used for transportation up and down - we used the thing invented by Elisha Otis in 1853 called... an *elevator.*
Posted by: gr | 18 July 2008 at 08:46 AM
In reply to methane being a better energy carrier (see post of gr):
Burning methane produces carbon dioxide, as we all know a greenhouse gas. Burning hydrogen only produces water and oxygen. So it's a cleaner and hence better energy carrier
Posted by: Tim | 02 September 2008 at 12:58 PM