Science Buddies: "Ask an Expert"

My son wants to do a project on Energy from mud. He is in 5th grade. Looks like he read something from library.
I read a little bit too on internet but its too high level for me to even explain and discuss with him.
what kind of hypothesis can we form?, what could be our variables, any help please?

Hi nissan,

We have a project on exactly this topic, "Turn Mud into Energy with a Microbial Fuel Cell — and a Dash of Salt":

https://www.sciencebuddies.org/science- ... p071.shtml

I agree that the inner workings of a fuel cell might be a little difficult for a 5th grader to grasp. The very basic idea is that there are bacteria in the soil that can help generate electricity (the full explanation involves chemistry, and how the chemicals produced by these bacteria interact with some metal pieces you put in the soil). The output you measure in this experiment is how often a tiny light blinks (bacteria produce more electricity = light blinks more often). So, even if he doesn't understand exactly how all the insides work, he might be able to understand that and its relationship to a variable he can control. There are a bunch of different variables you can test - how the power output changes over time, what happens when you add salt to the mud, the moisture level of the mud, different types of mud etc. Hope this helps!

-Ben

Thank you we will start on it and will let you know how it goes. Are there any real world applications of this type of energy.

Hi nissan -

I would check out the background tab of the project, including the Bibliography at the bottom, to learn more about real world applications. You can also just do a google search for "microbial fuel cells". The general answer is that this is a "clean" source of energy (like wind, solar, etc), but like many other sources of renewable energy, there are technical challenges we have to overcome to make them cheap enough to implement at a large scale.

https://www.sciencebuddies.org/science- ... background

I did the experiment with three types of soil or mud , not sure what to call

I took top soil from my backyard, compost and also river mud but not from bottom enough but just on the top may be.

Does anaerobic bacteria exist in these samples that i selected? I generated electricity but can I say its because of anaerobic bacteria or is it some other kind?

Could you explain please? I have been taking reading from a week, does the anaerobic bacteria stay alive from all these days?

Hi nissan - I am a mechanical engineer and not a biologist, so I actually don't know anything about what types of soil anaerobic bacteria live in. I took a look at the background tab of the project and it mentions some different kinds of bacteria, including "electrogenic bacteria" (bacteria that can generate electricity) and "the Shewanella species, which can be found in almost any soil on Earth".

You might be able to get more help in the Life Sciences forum if you need to find out what types of bacteria are common in the soils you mentioned.

Thank you so much. Where is the Life sciences forum? But your information is also very helpful

Oops - I'm sorry, I didn't notice that this post is already in the life sciences forum! (see how it says Life, Earth and Social Sciences at the top of the page). Hopefully someone with a better biology background will be able to help you here. But in the meantime, I would do more research on the terms I linked below.

yes, thank you, I posted it in there. I really hope someone replies.

I hope these links help. Anaerobic conditions are required for the more conventional electricity producing reactions. Oxygen is an electron acceptor and will interfere with the process, thus anaerobic (lacking oxygen) conditions are required.

http://www.altenergy.org/renewables/wha ... cells.html

"Microbial Fuel Cell Anode

When bacteria consume an organic substrate like sugar under aerobic conditions, the products of cellular respiration are carbon dioxide and water. However, when placed in an environment void of oxygen, cellular respiration will instead produce carbon dioxide, protons and electrons. It is therefore necessary to impart an anaerobic environment in the anode chamber of the MFC.

In mediator based MFC's, an inorganic mediator takes the place of oxygen in the bacterial electron transport chain. The mediator crosses through the bacterial outer membrane and accepts electrons that would normally be accepted by oxygen or other solubles. Once the mediator has been "reduced" it exits the cell full of electrons which it transfers to the anode.

In mediatorless MFC's the exoelectrogen sticks to the surface of the anode and uses an oxidoreductase pathway to directly transfer electrons through a specialized protein into the surface of the anode. Electron transfer mechanism may involve conductive pili, direct contact through a conductive biofilm, and/or shuttling via excreted mediator enzymes."

And here: http://en.wikipedia.org/wiki/Microbial_fuel_cell

" The release of the electrons means that the mediator returns to its original oxidised state ready to repeat the process. It is important to note that this can happen only under anaerobic conditions; if oxygen is present, it will collect all the electrons, as it has a greater electronegativity than mediators."


Cheers,
Colin