Charcoal as a media

[Paul Letby]

Hey guys, I'm going to open this up for debate, as things are getting a little off topic on my personal system discussion.  There have been questions as to the safety of charcoal as a media, and I'm sure there are questions out there regarding it's environmental impact.  So let's let fly with the questions and hash this out.  I'm definitely not the expert here, and I am hoping George will weigh in on the issues. 

 

Personally I decided to use charcoal based on the fact that I have free access to wood, and needed a cheap and light media for use in a GB supported by a light stand that's not meant to support a lot of weight.  I know that activated charcoal is used in aquaria as a filter media, so I'm pretty sure it's safe.  That said we all know that many things from tropical fishkeeping don't transfer to aquaponics very well.

[Bob Campbell]

I'm wondering what others are doing to initially add microbes.to the charcoal before adding it to a system.  I have read about people using compost tea, and seaweed extract.  I imagine simply letting it cycle like gravel would work too.

[Jon Parr]

Thanks for referring this thread, Bob. Good read. I have seasoned my char by soaking it in fish sludge from a swirl filter or settling tank. Cycling it through an overstocked system works good to, and will clean the water right up. 

[TCLynx]

Right Bob, worm casting tea, or compost tea can provide plenty of good microbes to colonize media but as noted, the bacteria exist all around and can colonize on their one naturally just like we can do it with gravel. 

As Jon Parr says, you can pre-cycle some media.  If you are planning to build a new system and can plan ahead and put media in paint strainer bags to season somewhere in an existing to be ready to seed the new system it often works a charm to help get cycling of the new system off to a good start.

[Harold Sukhbir]

Hi All,

I was wondering about the buffering requirements, if any(depends on the source water of course), with this media. With charcoal being somewhat porous, should provide more area for bacteria. I don't know if this will affect the media ratios in any way.

[Bob Campbell]

I've gotten very excited about Bio-Char and made a post on my blog with links and videos to the most interesting information I have been able to find.

Click here for my blog  post  ->   Bio-Char

[TCLynx]

The buffering requirements with charcoal will greatly depend on the type of wood and source water I think.  I know some one who did tests where the charcoal did seem to bring pH down but others where the pH stayed high so testing on particular charcoal and the ash that comes along with it would be important.

Charcoal is porous but so is lava rock and expanded clay, slate, shale.  Now the porous nature of the media may allow more bacteria colonization to handle the nitrification, the truth is the solids mineralization happens in a far less porous environment and is likely to defeat the porous environment by covering it with bio-slime if you are not removing the solids so the media being more porous may be rather beside the point if you are doing simple media bed aquaponics without solids removal.

[Jon Parr]

Exactly! Well said, TC. I have a system with no media at all, and it works great. The UVI model really has no "media", technically, and they are basis for most all commercial systems. So adding a super porous media in lieu of a less porous media may be like having 50 car batteries installed in your car, when only 1 is sufficient.

And the pH tendency of char probably has more to do with "how" the char was made, more so than "what" the char was made from. Un-charred wood, and sticky low temp char may bring pH down. Ash brings pH up. Completely cooked medium to high temp char should ideally be nothing but carbon, and fairly pH inert. Whether you start with soft pine, or rock maple, pure carbon is all that remains. Porosity and density, however, reflect the nature of the original wood.

The big benefits of char, for me, are
1- local. Right in my yard, zero energy costs to make and transport, and the energy byproduct from making char can heat my GH, etc
2- lightweight. It does get heavier when it finally soaks up water, but for things like vertical towers, it's a lifesaver.
3- sequesters carbon. While I don't subscribe to "the inconvenient truth", and Al Gore really stumbled upon "a convenient profit", there is merit in locking up some carbon back into the earth, and out of the air.
4- nutrient storage. This is key. The ability of carbon to store organic and inorganic nutrients is incredible, and the interaction between plant root hairs and bacteria to retrieve those nutrients is amazing.



TCLynx said:

The buffering requirements with charcoal will greatly depend on the type of wood and source water I think.  I know some one who did tests where the charcoal did seem to bring pH down but others where the pH stayed high so testing on particular charcoal and the ash that comes along with it would be important.

Charcoal is porous but so is lava rock and expanded clay, slate, shale.  Now the porous nature of the media may allow more bacteria colonization to handle the nitrification, the truth is the solids mineralization happens in a far less porous environment and is likely to defeat the porous environment by covering it with bio-slime if you are not removing the solids so the media being more porous may be rather beside the point if you are doing simple media bed aquaponics without solids removal.

[Bob Campbell]

I've used charcoal from Cash & Carry and it has worked well after I got the pH under control.  It appears that the high temperature method of making bio-char creates a more friable form of charcoal.  I'm wondering if you are making your own and which method you use.  The High Heat method uses two barrels and the fire is lit in the space between the small barrel and the outside barrel.  The Low Heat method uses only one barrel and the entire barrel is lit at the top.  It's called a TLUD.

Jon Parr said:

Thanks for referring this thread, Bob. Good read. I have seasoned my char by soaking it in fish sludge from a swirl filter or settling tank. Cycling it through an overstocked system works good to, and will clean the water right up. 

[Paul Letby]

I kinda used a red neck approach and simply started a fire, waited for it to die down to coals and doused it with water.  Worked for the limited amount I needed.

[Jon Parr]

I like it, Paul. A doused fire always yields some charcoal.

Bob, sorry I didn't see your question in your last comment until just now. I used a TLUD for my first few runs, then made an indirect retort. Now I am nearly finished with a retort/pizza oven/rocket stove/water heater. Sound hot? That's because it is hot! At the bottom of the contraption is a small rocket stove. The exhaust goes around a sealed barrel retort full of chips. The retort has a single pipe vent that is plumbed back to the rocket fire to burn the syngas. The heat/smoke escapes above the retort into the rear of a dome pizza oven, refracting heat to the cooking surface, and then the smoke goes thru a heat exchanger to heat my 7K gallon FT. The exhaust should be cool enough at that point to condense out the water, called wood vinegar or smoke water, which is beneficial for germinating seeds and kills pests. Hot damn, that's pretty cool. I still have to make the door for the retort area, dome the pizza oven, and plaster the whole thing to make it pretty. I plan on having it finished for my next round of workshops on the 15th

Come check it out.

[Vlad Jovanovic]

Damn Jon, talk about multi-tasking efficiency. Sounds like a really neat contraption.

[Paul Letby]

Wow that does sound cool!  Any pictures?