Purple Bacteria Turns Poop into Power

Researchers have found a way to reduce carbon emissions from human sewage and produce hydrogen energy at the same time, all with a lovely purple hue.

We might not often think of human waste and sewage as a problem for our climate change reduction goals, but it is. Research has shown that our sewage and waste water treatments systems are responsible for a significant level of insulating gasses that are warming our planet. That release is down to a number of things, including methane and nitrous oxide being produced as drain water is purified.

However, recent studies have shown that we may have been underestimating the level of greenhouse gasses our sewage treatment produces by around 23 percent specifically because we’ve failed to account for the CO2 released during the processing phases of treatment.

Interest in how to reduce this insulating gas output is high, and researchers are looking into how we might make this process more environmentally friendly. There’s even been some limited investigations in how to harness the biomass in wastewater and put it to good use in the form of energy and usable gasses, something that could significantly offset the so-called “bad” insulating gasses we are producing.

Publishing this month in the journal “Frontiers in Energy Research“, scientists from King Juan Carlos University, Spain, have found a way to harness photosynthetic bacteria to clean up our current waste management strategy.

Purple Poop Power

Most of us are familiar with photosynthesis: the process by which leaves generate energy when exposed to sunlight. A variety of bacteria are also capable of doing this trick, and they’re not confined to doing it while wearing green. Photosynthetic pigments can occur across most of the color spectrum, including purple. Thus, we have phototrophic purple bacteria (PPB).

Of course, their color isn’t nearly as important as what they can do. Some forms of purple bacteria caught the research team’s eye for this study because of the their to use carbon dioxide to produce hydrogen when exposed to an electric current. That’s quite intriguing, if we want to minimize CO2 while also creating energy.

So the researchers set about testing the bacteria. To do this, they used a mix of different species of PPB to see how different environments changed what the bacteria would produce. They also played around with exposing the bacteria to a current, using both the standard positive as well as a negative charge.

A key finding was that the conditions in which the bacteria produced the most hydrogen also minimized CO2 output, which is a win-win scenario.

To unpack that a little further, the PPB would produce different things if the environment was altered. For example, they produce more hydrogen when there are fewer proteins in the waste water. This is doubly useful if the system were to be adopted on a broader scale, because it would mean that, potentially, we could tailor the environment to produce different byproducts based on our needs.

PPB are also capable of producing biodegradable polyester, something that could be useful. The researchers refer to the bacteria as being like a “Swiss Army Knife”, and it’s not difficult to see why.

Another key finding was that, for the first time, the PPB were observed using electrons from a cathode and taking more carbon from the waste material as a result, something that would further reduce CO2 output in the waste management process.

“One of the most important problems of current wastewater treatment plants is high carbon emissions,” co-author Dr Daniel Puyol of King Juan Carlos University said in a press release. “Our light-based biorefinery process could provide a means to harvest green energy from wastewater, with zero carbon footprint.”

We would need to production and infrastructure changes to deploy this effort, so that would have to be factored into the broader environmental costs. However, that the process itself could yield hydrogen as a fuel source while doing something with the CO2 byproduct of waste management processes is incredibly exciting. The researchers also say that they are looking toward ways of maximizing hydrogen production, further increasing this research’s worth and marking this as an innovation to watch in coming years.

Who knew that waste management could be this exciting?

Photo credit: Getty Images.

55 comments

Shae Lee
Shae Lee11 days ago

Thanks for sharing!

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FOTINI H
foteini chormpou12 days ago

wow!

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Ingrid A
Ingrid A16 days ago

Thanks

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Loredana V
Loredana V17 days ago

Wow! Thank you.

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Laura R
Laura R17 days ago

Thank you.

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Elisabeth T
Elisabeth T17 days ago

Thanks for the information.

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Clare O'Beara
Clare O'Beara17 days ago

No shortage of humans so no shortage of waste.

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Clare O'Beara
Clare O'Beara17 days ago

Dublin's Ringsend plant uses bacteria to eat all the waste in the sewage including fats. Then sunlight and added UV light to sterilise it.

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Clare O'Beara
Clare O'Beara17 days ago

th

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Louise R
Louise R18 days ago

Thanks

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