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Bacterial Hydrogen Production from Confectionary Waste

23 May 2006

Sweeth2
The bioreactor. Note the fan at right, powered by a fuel cell using the resulting H2. The gas passes via a glass “trap” to capture excess moisture.

In a feasibility study funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC), bioscientists at the University of Birmingham have demonstrated that certain bacteria can produce hydrogen gas as they consume high-sugar waste produced by the confectionery industry.

The sweet waste was supplied by Birmingham-based international confectionery and beverage company Cadbury Schweppes plc, a partner in the initiative. An economic assessment undertaken by another partner, C-Tech Innovation Ltd, showed that it should be practical to repeat the process on a larger scale.

As well as energy and environmental benefits, the technique could provide the confectionery industry (and potentially other foodstuff manufacturers) with a useful outlet for waste generated by their manufacturing processes. Much of this waste is currently disposed of in landfill sites.

In this project, diluted nougat and caramel waste was introduced into a 5-liter demonstration reactor. The bacteria, which the researchers had identified as potentially having the right sugar-consuming, hydrogen-generating properties, were then added.

An adapted form of a harmless strain of E. coli broke down the confectionary waste, producing hydrogen and organic acids. Naturally occuring Rhodobacter sphaeroides then was introduced into a second reactor to convert the organic acids into more hydrogen.

The hydrogen produced was fed to a fuel cell, in which it was allowed to react with oxygen in the air to generate electricity. Carbon dioxide produced in the first reactor was captured and disposed of safely, preventing its release into the atmosphere.

Waste biomass left behind by the process was removed, coated with palladium and used as a catalyst in another project, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), aimed at identifying ways of removing pollutants such as chromium (VI) and polychlorinated biphenyls (PCBs) from the environment.

The reactors used by this parallel initiative also required hydrogen and this was supplied by the confectionery waste initiative too, further underlining the benefits offered by the new hydrogen production technique.

Hydrogen offers huge potential as a carbon-free energy carrier. Although only at its initial stages, we’ve demonstrated a hydrogen-producing, waste-reducing technology that, for example, might be scaled-up in 5-10 years’ time for industrial electricity generation and waste treatment processes.

—Professor Lynne Macaskie, University of Birmingham School of Biosciences

As well as confectionery waste, the study tested the viability of potato extract as a feedstock for hydrogen-producing bacterial action. This did not yield promising results as the potato starch proved difficult to break down with the bacteria used.

The team is now engaged in follow-up work which will produce a clearer picture of the overall potential for turning a wider range of high-sugar wastes into clean energy using the same basic technique.

The 15-month feasibility study—Biological Hydrogen Production from Crops and Sugar Wastes—received EPSRC funding of nearly £24,000 ($US45,000).

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May 23, 2006 in Bio-hydrogen, Biotech, Hydrogen | Permalink | Comments (7) | TrackBack (0)

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Comments

I realize it is early, and these things are fun to hear about, regardless ... but we know yeast will turn sugar molecules to ethanol pretty 1:2 as in:

6H12O6 → 2 CH3CH2OH + 2 CO

How do H2 bacteria compete? Is there a simlar equation? I see, from the Biochem link above:

"The FHL complex comprises formate dehydrogenase and hydrogenase-3 and its function is to oxidize formate (an end-product of the mixed acid fermentation) to equimolar amounts of CO2+H2, coupling formate oxidation by formate dehydrogenase H to proton reduction [27]."

That sounds like more energy is given up as CO2 at the front end, in generating the H2.

Are we back to the same old story? Either use/sequester CO2 made in the H2 production operation, or you are better off from an energy/greenhouse standpoint shipping the carbon (in this case as ethanol) to the end customer.

First, the chemistry. I believe the reaction should be:
C6H12O6 -> 2CH3CH2OH + 2CO2
Note: 6 Os on the left, 6 Os on the right.

Other than that, an excellent question. Ethanol fermentation is a well established technology. Liquid fuel is far superior to gaseous fuel.

While electricity is a nice final product, we need a replacement for Middle East oil.

it didn't space out well in text but my "2 CH3CH2OH" above means "2" complete "CH3CH2OH" for 4 carbons. i stole the equation itself from the fermentation section of the wikipedia ethanol page:

http://en.wikipedia.org/wiki/Ethanol#Fermentation

NO, "2 CH3CH2OH" or "2CH3CH2OH" was not the mistake. Note "Os" refer to oxygen, not carbon ("C").

Your reaction, as printed, indicates that carbon monoxide (CO) would be formed. You missed the last character from wikipedia.

oh, you're right. i didn't even notice that. i cut it off in my cut and paste and thought it said co2 all along.

my standard proofreading skills at work :-(


H2 yield as described is going to be horrendously low compared to the example of ethanol fermentation, since most of the products of the fermentation in this case are the mixed acids. The example of coupling to rhodobacter sphaeroides is only mentioned in the paper as an aside, and no data are given, so there's no way to know the efficiency. If hydrogen production is the main goal (rather than metal remediation as seems to be the case here), there are other bacteria that are a lot more efficient than the coli used here.

Andrew,
You are right. Seems like the normal hot air from the hydrogen crowd. A two step fermentation does not sound very workable. The use of specific species does not sound very robust. How do you keep normal anaerobic bacteria out? Sterilize the feed? At what cost?

Nice lab project. Not for real world application.

In the real world you could do one of two things:
1. If a high portion of the feed organics is pure sugar, do an ethanol fermentation.
2. If not, just dump it in an anaerobic digester and produce biogas: mostly methane (CH4) and CO2. The biogas can be:
a. used to power a generator,
b. converted to syngas and then converted to liquid fuels via Fischer-Tropsch, or
c. converted to hydrogen in a steam reformer.

I am willing to bet all of these would yield more energy and be much easier to impliment than the proposed process.

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