Thank you to Skillshare for sponsoring this episode of SciShow. [♩INTRO].

The stuff that you flush down the toilet isn’t just waste, the organic material it contains could be used as an energy source, if we could figure out how to use it effectively. That’s what scientists in Spain might have found a way to do.

In a new paper in the journal Frontiers in Energy Research, they report that purple bacteria could help us harness that energy and reduce carbon emissions at the same time. Purple bacteria, or purple phototrophic bacteria, to be more precise, are a group of bacterial species that can make their own food using photosynthesis, kind of like plants and algae do. Their color, which actually ranges from red to purple, comes from pigments like carotenoids, which they use to capture light energy.

And while plants use that light energy to convert carbon dioxide and water into sugars and oxygen, purple bacteria are a lot more flexible. They can start with lots of different ingredients. And depending on the source of carbon they start with and environmental factors like temperature and light intensity, they can make a wide variety of products, including small proteins and even a type of biodegradable polyester!

But it’s their ability to produce hydrogen, known as biohydrogen in this case, because it comes from living things, that has scientists excited. Some engineers think biohydrogen could be the fuel of the future because it can produce a lot of energy with little or no carbon emission, and the main byproduct of burning hydrogen is water. Which is pretty great.

Unfortunately, we’re still working out the best ways to produce, store, and deliver biohydrogen. And purple bacteria could be part of the answer. Researchers were able to take purple bacteria growing naturally in wastewater and cultivate them by shining infrared lamps on a sludge mix.

Then, they manipulated the carbon and nitrogen sources they gave these bacteria to see which maximized biohydrogen production. They even tried offering them electrons by sticking one end of a battery into the flask they were growing in. In the end, two compounds common in wastewater, malic acid as a carbon source and sodium glutamate as a nitrogen source, produced the most hydrogen while minimizing carbon dioxide emissions.

Using this mixture, the bacteria produced about 400 milliliters of hydrogen gas per liter of bacterial soup. That’s about enough to drive a hydrogen-powered car 3 meters. While that might not seem like a lot, it could add up quickly.

I mean, the U. S. has to process some 128 billion liters of wastewater a day. But what really intrigued the researchers was that the bacteria were able to take the extra electrons from the battery to use up more of the carbon they were given.

Although that wasn’t exactly what the researchers were aiming for, it could point to a strategy for reducing the carbon emissions produced by wastewater treatment. So the research represents important progress on the road to converting our poop into clean, green energy. Or maybe purple energy?

Why not!? And speaking of clean energy, last week, scientists unveiled bionic mushrooms that can produce electricity, in a new paper in the journal Nano Letters. The current they generate is thanks to cyanobacteria, a kind of aquatic bacteria, which the researchers 3D-printed onto plain old button mushroom caps, along with a conductive graphene ink.

While they aren’t going to replace your rooftop solar panels any time soon, these bionic mushrooms are the first example of an engineered relationship between different types of organisms, and maybe a glimpse at energy technologies to come. Solar panels are basically an engineer’s best attempt to mimic a plant. But plants, algae, and bacteria that photosynthesize are a lot better at capturing the sun’s energy than we are.

Cyanobacteria, for example, are almost 100% efficient, which means for every photon of light they capture, they generate one electron. For comparison, the best solar panels you can buy and put on your roof are about 20% efficient. So for decades, scientists have been working on methods to use living organisms to generate electricity more efficiently.

But cyanobacteria are aquatic and tend to be quite finicky. They don’t like growing on artificial surfaces. The researchers behind the bionic mushrooms were trying to figure out what they could grow the bacteria on, when they realized that lots of species of fungi partner with other organisms.

Apparently this dawned on them over lunch one day, because, you know, scientists eat mushrooms sometimes. The team wondered if they could make that kind of relationship happen. So they bought some white button mushrooms from a local grocery store, the same kind you might pick up to make a tasty batch of stroganoff or sprinkle on your pizza.

Using a 3D-printer and ink made of graphene nanoribbons, super tiny strips of carbon atoms arranged in a lattice, they made a mini grid on the mushrooms where current could flow. Then, they 3D printed colonies of cyanobacteria on top in a spiral. The water and nutrients provided by the mushroom cap helped keep the cyanobacteria alive.

They lived longer on a living cap than on a silicone version or on one killed with vinegar. And the electricity-conducting ink was able to snag some of the electrons the live cyanobacteria produced during photosynthesis and pass them off to connecting wires, generating a current. When the researchers shined light on one of these bionic mushrooms, it generated an electrical current of about 65 nanoamps, or billionths of an amp.

That’s... not a lot. It takes a current of roughly a full amp to charge your cell phone. But the researchers are working on tweaking this system to produce more electricity.

If they could make it more efficient or string together lots of these mushrooms, they might be able to create a whole new kind of solar panel. But really, what’s exciting about this is that it worked at all. I mean, the researchers merged cellular biology with nano-engineering to create living tech.

And that could open the door to harnessing other microbial superpowers. Designing the tech of the future will take a lot of brainpower and some really clever scientists willing to try things like 3D printing on mushrooms. But preparing your website for future changes to browsers and mobile devices is something you can do yourself with a little help from Skillshare and web designer Ethan Marcotte.

In his class on responsive web design, he teaches you how to make beautiful sites that don’t have to be modified for each different screen they’re viewed on. What I love most about this class is that you don’t just learn how to make the webpages, you learn how to think about page design in a whole new way. And right now, Skillshare is offering SciShow viewers 2 months of unlimited access to all their classes for free.

So you can take this class, or any of their more than 20,000 other classes! So you can improve your websites and learn how to cook a tasty mushroom ravioli all in the same day. You can follow the link in the description to check it out for yourself! [♩OUTRO].