I wanted to start a pre-compost bin in the kitchen, but I knew my mom probably wouldn't appreciate the smell.
I had been looking at several instructables on kitchen/indoor composting and terrarium building. The indoor compost bins seemed to use charcoal filters. One of the terrariums had a bottom layer of activated charcoal. "hmmm...what if I combined the two?" thus this hybrid indoor compost bin and planter was born.
The idea is that the plants above the compost (as well as the activated charcoal) smell fantastic and filter out the compost smell below them. It also looks cooler than your average indoor compost bin, so you might not mind having it sitting there on the kitchen counter top (particularly if you use nicer looking containers than I did). The bin below the plants can be exchanged with a clean bin when the compost is dumped in a larger compost container or pile.
My inspirations, which may be of use to you and your further improvements on this idea:
Step 1: Materials
1. Containers (2 or 3). These were 99 cents each at home depot, but you may have some lying around. They should be the same size. Best if you have (3), the third one is useful for when you swap compost out. I used clear containers, but you may want to use solid containers so you don't have to see the compost (or you could add duct tape or paint to them).
2. Activated charcoal. You can make this (basically free) or buy a jar from a local store, usually stores that have (pet) fish products also have them. I needed almost a full jar of this stuff.
3. Sand or pebbles (gravel is ok). If you decide to use pebbles, make sure they are small enough. You want fine pebbles no larger than a fingernail (and I don't mean the fingernail on your green thumb). I needed about 1.5 solo cups worth.
4. Potting soil. Expect to use much more soil than gravel
5. Indoor/shade plants. I bought 4 small plants and that was enough.
6. Duct tape
7. Utility knife (use a bigger one than is pictured). I ended up using a box cutter
8. Scissors. Make sure they are sharp
9. Mesh. I used fiberglass mesh, like the type used for screen windows and doors
Step 2: Cut Holes
You need to cut holes in both one lid and the bottom of one of the containers. The container will be used for the planter and the lid will be for a separate container that will house the indoor compost, Use a boxcutter knife if you have one. You can use scissors, but your holes may end up imprecise.
On that note, your holes don't have to be perfectly straight or match with each other, although the container will sit on top of the lid so the closer they match, the better.
Leave some room on the edges and preferably a strip in the middle.
Step 3: Cut and Attach the Mesh Screen
Measure and cut your mesh to slightly larger than the dimensions of the holes you have cut in the lid and the container. I was able to cut the fiberglass mesh screen with scissors.
Lay the mesh on top of the holes and duct tape the mesh. On the lid, I only duct taped the mesh to the underside of the lid. On the container I duct taped on the inside as well, as you can see that the charcoal was finding its way between the mesh and the bin when I did not.
You can tidy up the tape with scissors or by folding the visible edges of the tape over (particularly applies to the lid).
**another option is to line your planter bin with mesh instead of taping it. This requires more mesh if you are just using scraps than you might have, but might be an option if you are concerned about it holding. You might want to consider adding super glue. I did not.
Step 4: Add the Layers to the Container
Once you have the mesh taped (or superglued and taped) on to the container and the lid, you will add 3 layers to the container you have been modifying: activated charcoal, gravel/sand and potting soil.
First, make sure the mesh is secure and the tape is holding. I put a 2nd container underneath the one with the mesh in case it wasn't.
Your first layer will be the activated charcoal. If you don't want to buy this you can also make it from a charcoal log that has been left in either a grill, fire pit or fireplace long enough to become blackened. I needed nearly the full jar of charcoal for my containers. This is the main odor filtration, and also keeps water from seeping down further than the sand/gravel layer. Spread the charcoal out. You want this layer around 1/4" thick, but a little more isn't a problem.
Your second layer is either sand, pebbles or gravel (or a mixture of any of these materials). If gravel or pebbles, you want to make sure the individual stones are not too large, no bigger than a fingernail (not including your thumb). This is secondary filtration and helps hold the soil in place. Sand would do a better job at water retention than the other options obviously but has the caveat of also being heavier once wet (when you water your plants). 1.25 or so solo cups of the material was enough to do one layer of the small gravel mix I found locally.
The third layer is soil. You will be putting the plants in shortly, so you don't have to add too much until after the next step.
Step 5: Plant Your Plants
Lastly you will be placing your shade plants in the container with the partially mesh bottom. Before I did this I shook the container gently and moved it like a sieve up and down while there was still an outer container to catch loose particles.
I needed 4 small shade plants to cover the area available in my container, but this will depend on the size you have available.
Once the plants were positioned I then added soil around them. I needed more soil than I thought I would to hold the plants in place.
Step 6: Use Your Indoor Compost Planter!
You can now use your compost system. The mesh lid goes on the top of one container. This container is placed below the planter container. Eventually I will be adding velcro on the lid so it stays attached to the bottom of the planter. I will also be adding handles to more easily lift the planter.
Add non-meat, non-grease food waste to your compost and remember to change it often. This is just a pre-compost bin. Empty it in your compost pile or bucket to make room for new waste. I would suggest saving the third bin to use when you are doing this, swapping out the kitchen compost bin.
Simply place your compost planter in a convenient location and don't forget to water your plants and enjoy their organic scent!
(at the time of this article's publication the compost system has only been used for one day. The smell seems to be contained, although I would like to add the previously mentioned modifications for easier use)