Getting electricity directly from the soil

This is my first post at Permies.

I wonder if anyone has posted about Plant-e here yet? If not, that would blow me away. It is a low-tech system of getting electricity from garden soil.

Here is the CEO's TED Talk:

www.youtube.com/watch?v=6XXDoOwY8LE

I'm not a fan of the fashionable so-called "alternative energy" systems. Even solar strikes me as ugly and clumsy. I think there are a lot more elegant solutions like Plant-e out there staring us in the face. We just need to wake up.

Certainly the idea of an 'earth battery' has been discussed here before [ https://permies.com/t/40/55194/true ]  but this looks like a more interesting early-end-of-development idea.  Pretty low energy output it looks like at the moment, but with some technological boosts, may have a role in localized power production.

A link to some FAQs regarding the company and the technology (including a link to the PhD thesis of the CEO) can be found here:  http://www.plant-e.com/en/plant-e-faq/

I haven't seen any microbial fuel cells with high power outputs yet. The following better explains plant-e for nerds. It requires aquatic plants, hence a lot of water and in their case plastic to hold it. It would be interesting to try if you had a pond and a bunch of carbon plate electrodes for a larger surface area.
One of the following videos in Italian shows a pot plant outputting 180mV and 10uA, which isn't much power.

The other MFC example below may be better and uses Soil + Microbes + Blood meal + Electrodes.

I also remember reading about a filamentous organism in river sediment that exchanged electrons between upper and lower layers. I can't remember if it or other aerobic organisms were photosynthesising in the upper layer providing the electrons for exchange, I can't find that article now...

Now it's been discovered that if you combine organisms you can also create anaerobic microbial photosynthesis, and if I understand that correctly, you may not need the plant and electricity could be harvested in tubes or bags like those used in algae production, while being fed waste water https://news.wsu.edu/2017/01/09/wsu-researchers-discover-unique-microbial-photosynthesis/

Wow! These are great responses.

John, thanks for bringing up earth-batteries and posting a link. So crucial. I welcome more links.

Craig, thanks for the videos, and thanks for pointing out that aquatic plants are necessary for the Plant-e system. I've known about them for more than a year now, but for some reason never bothered digging deeper. The benefits of sharing, I guess.

I think this is finally a really good use of LED lights, along with little portable keychain lights for walking at night...

The plant light is evolving...  Here are two examples now:




And here is an article, if you prefer to learn that way:  LED Microbial Battery/Plant Generated Light

And a picture below.  The video above shows the light brightening when the plant is touched.  It would be fascinating to try other things, like breathing on it, right?



I want to make one!!

I wonder this can also be done with composting or while growing mushrooms?  

Having read about the redox interactions between Biochar and soil bacteria I was thinking that Biochar might be a good anode and cathode material for microbial fuel cells.  Not much time at the moment, but a quick google search shows that work has been done that demonstrates this.  Just putting this out there in case others wanted to dig into this more.  Very exciting space!  Thank you.

Telluric currents are a phenomenon where extremely low frequency currents run at or just below the Earth's surface, moving sunward. I need to find the link to this for a future edit, but I am sure I read that they were integral to early telegraph operation.

I wonder if channeling these into a giant earth battery setup would have any effect on the soil biology.

I also wonder if building a pond as a microbial fuel cell in the middle of the giant earth battery would ameliorate the pond/microbial fuel cell's efficiency or output.

-CK

In the early days of telegraph they would charge the batteries via a ground system,
A ground rod would be driven and an insulated wire attached and ran for a couple of miles, generally the wire was supported just a few feet above the earth, finally another ground rod was driven and the difference between the line and the new rod would be adequate to charge the batteries.

A difference of potential can be found within just a few hundred feet, although not an adequate source to accomplish work.

Though using the plants as an electrical source is cool ... consider using the potential difference between the soil and the air - actually, an antenna waaaay up in the air. There's much on the Web about this. Please use caution as there's quite a bit of juice that can be extracted from that set-up. Then there's the storage issue. Quite a pain. As we move away from the AC-based system, and even the typical DC system, there's much to learn when considering pulsed DC and cold electricity. (Yes Virginia, cold electricity does indeed work and it's real) You must consider Nathan Stubblefield when discussing the early inventors of ground-based electricity. (http://www.angelfire.com/ak5/energy21/earthbatteries.htm) He was the Man, as it were. Be careful out there as there's many who will sell you a load of horse hoo-ey...and it will only run a few LEDs. History and doing the experimenting yourself is still the best - it does help to have someone to bounce a few ideas off of...

Cheers from here,

Col