After a few months of marriage I decided to build a compost bin to reduce the amount of trash we were throwing out. I got some materials, drew up a plan, and threw something together. Well, that something has done spectacularly - we've reduced our garbage to a half-bag a week, we no longer have a horrible odor when opening the garbage can, and best of all we get great soil for our garden. Our compost bin has worked so well that friends remarked that they wanted one. So last year I made one as a gift for a friend who was expecting her first baby. But this time I took pictures.
It's a simple black cube, two feet to the side, with a separate lid that can be chained to to the bin for security and a wire mesh at the bottom to let water out, worms in, and prevent rodent incursions. I think it's a good design for many reasons - the locking lid works well for keeping out animals in our small yard and suburban/rural area and the discrete size and shape means that neighbors, and especially the landlord, have never complained. The black finish also heats up the interior so that the compost inside essentially cooks, decomposing so fast that even meat*
disappears before it has time to smell.
I've got a list of all the materials
you'll need to make the frame and lid down towards the bottom of this post. I used pressure-treated lumber for the frame because I wanted it to last in what I knew would be a hot, wet, and organically active environment. I used paint on the inside for the same reason - paint on the outside is mainly to help it collect heat from the environment. At this point in the evolution of the design I'm fond of stainless steel screws but I've found that ceramic-coated work just as well with the pressure-treated lumber. The only drawback there is that they seem to only be available in longer lengths as deck screws.
What material you use to skin your box is entirely up to you. Factors to consider are cost, weight, durability, ease of replacement/removal, and so on. For the first bin, the one I made for my wife, I used a sheet of interior paneling
made of compressed fiber material because 1) I got it for $2 and 2) I didn't know any better. For the next bin I used a sheet of water-resistant tile
from the same company, and made of the same material, because I had seen how well the waterproof side worked and I got half a sheet for $5.
I decided against plywood because of weight, and luan always felt too flimsy to me. Like I said though, use what you like - right now I've replaced two sides of my bin with a piece of wood paneling (bought on clearance) because after three years the interior fiber paneling finally rotted out at the bottom. Anyways, onto the frame... (All pictures are linked to the full version in my gallery. Some of them are quite big, so only click if you want a good closeup.)
Start with your 2x2's and cut them into pieces 22 1/2" long (assuming your 2x2 is 1 1/2" across. If not, adjust your measurements). Sand down the rough corners and edges and assemble each one into a square 2' by 2', using the stainless steel deck screws to hold the pieces together. I used some of the paintable silicone sealant to provide a seal around the screw holes but it's not necessary.
Cut your remaining 2x2 into pieces 21" long and use those to affix the two squares together, again using the stainless steel deck screws. You should now have a plain cube 2' long on each side.
Go ahead and paint the frame now, making sure to give it a good two or three coats and lightly sanding between coats for proper adhesion.
Here you see the painted frame drying between coats, resting on my current bin.
While the paint is drying on the frame start applying paint to your skin material. I suggest painting it as a whole piece first and then cut out the individual panels for each side. With this one I decided against painting the waterproof side of this paneling. That surface was waterproof enough on its own and I didn't think it would hold paint without a lot of sanding.
Keep in mind that one side will be in contact with hot, humid, actively decomposing organic matter and the other side only has to deal with sun, rain, and snow.
While the paint dries on the skin start work on bottom screen. Take one of your 1x2s and cut it into four pieces 22 1/2" long. Take these, lay them down on their broad side, and use your stainless steel screws to assemble them into a square 24" to a side. Give it a quick coat of paint and let it dry.
Cut your hardware cloth to fit over the square. Give the hardware cloth a coat of spraypaint as a primer and then lay it down on a flat surface while you apply some of your latex paint to both sides. One coat is fine, two is better but probably not necessary.
Use your short screws and washers to screw the cloth and the frame together.
Cut your large sheet of skin material into several panels for the sides. Sand down the cut edges to a smooth, rounded surface and apply two or three coats of paint.
Attach the bottom screen to whichever side of the cube you've decided is the bottom (for strength I try to keep the two original squares I built as the top and bottom). Use 1 1/2" stainless steel deck or pan-head wood screws to attach them. Here I used deck screws and covered them over with the paintable silicone sealant.
I arrange it so that the hardware cloth is sandwiched between the cube and the bottom frame - this helps hold the cloth in place. If you're confident in how well you built the bottom frame go ahead and switch it around.
Now you can attach the side panels to your cube. For this and my original bin I used galvanized roofing nails, but after repairing the two rotten sides this year on my bin I've decided that stainless steel pan-head screws are much better, if only for the ease of removal in case of future problems.
Take the two door chains and give them a quick spritz with the spraypaint as a primer. I then dipped them in the can of latex paint but you can get away with attacking them vigorously with a paintbrush.
When the paint is dry attack the chain portion in the upper corner of one face of the cube, and then in the same corner on the opposite face of the cube.
Here we're starting to make the lid. To best resist curious critters (and ice blocks that fall off my apartment roof) I've made it out of some more 1x2 and two layers of skin material. Since the lower layer of the lid is only in contact with heat and humidity but no actual compost and the upper layer only needs to withstand the weather you can use other materials than what you used for the side panels of the bin.
Make a 2' by 2' square just like the bottom screen and attach a piece of skin material to it. Cut a 21" piece of 2x2 and put it across the middle as a brace for strength and as a place to anchor the handle. Anchor it from both the side of the square and the underside of the skin.
Place your top layer of skin and mark where the brace falls, then mark the place for your handle. Attach the top skin and then the handle. Again, use the stainless steel screws here. In opposite corners attach the slide parts for the two door chains.
Give everything a couple of coats of paint.
And now you're done. This photo shows the inside of the bin - note that you will have edges where compost matter will collect. It's not necessary to constantly turn them but make sure to scrape the edges of the bin every so often.Parts list
Meat in your compost
|1 each for the top and bottom of the frame and 1 for the vertical struts in-between
||1"x2"x8' furring strip
|1 for the bottom screen and 1 and a quarter for the lid
||1/2" hardware cloth
|For the bottom screen
|One each in opposite corners
||5 1/2" handle
|In the middle of the lid
||2 1/2" ceramic coated deck screws
2 1/2" stainless steel deck screws
|16 for the frame, 4 for the bottom screen, and 6 for the lid
If available, there are ceramic coated deck screws that work just as well as stainless that are much cheaper
||3/4" stainless steel flat-head screws
|Affix the hardware cloth to the bottom frame
||stainless steel washers
|Affix the hardware cloth to the bottom frame
||3/4" stainless steel round-head screws
|Attach the side panels to the frame
||1 1/2" stainless steel screws
|Attach the bottom frame to the main frame
|12 - 16
||1" stainless steel flat head wood screws
||1.68 - (2.24)
|To attach the door chains and handles to the frame and lid
||Black spray paint
|Primer - optional
||Gallon black exterior paint
||3.99 - 23.96
||3.99 - (12.88)
|Protection from moisture and increase heat absorption
I was lucky enough to find a gallon of almost pure black exterior flat in the "goof" bin at my local hardware store. Two quarts of a ready-mixed enamel like Krylon would probably work just as well.
||Tube paintable silicone sealant
|For sealing seams, over screw holes, and general water-tightness - optional
||$41.00 - $60.30
Despite what you may think or have heard it is possible to compost meat scraps, fat, and even dairy products in your compost bin. However you can't just throw Junior's leftover hotdog on top of the pile and wait for it to rot - there are some considerations to be made first.
Does your bin get warm enough? Here in western PA our summers typically get into the 80s. Inside the bin this translates into an air temperature of well over 120 degrees Fahrenheit. Because of the black sides absorbing heat from the sun even in the fall we'll typically see inside temperatures over 90 degrees. Placing the bin on the southern side of the apartment helped a lot in that regard.
Is anyone maintaining the compost? If you just keep throwing new material on top of old you'll soon get a moldy matted anaerobic mess. For best results, especially with meat, you should be turning the compost at least once a week.
Do you have enough finished compost to cover the meat/fat/dairy? To keep down flies and other insects it's best to dig a small well inside the bin and cover the meat with other material. For this reason I don't recommend starting to toss in meat until you've had the bin going at least three or four months, or until you've created about 7" of finished compost.
Some other things to consider: Because of the concern for animal bacteria we use a compost sifter and fill one of those Rubbermaid storage tubs with finished material. We then let it sit, untouched, on a corner of the porch for nine months before we use it. Bones take a long time to break down, up to three years for a chicken wing bone and longer for anything bigger, so when you're turning your pile and come across a bone that's been picked clean (they no longer have an yellow oily sheen about them and are usually black with encrusted compost) you'll probably want to pick it out. If you don't you'll soon find it hard to get your shovel into the compost without striking an immovable bone. The photo to the right shows all the bones I picked out of my compost bin after the first couple years. For dairy I try to mix liquidy things (sour cream, cottage cheese, etc...) with warm water and then pour it into the pile. For solid stuff (cheese) I like to cut it into half inch cubes - the smaller size helps speed decomposition.
I've included some link to other places on the internet discussing the composting of meat.
And that's it. Here's a quick model I made in Google Sketchup
to show how the frame and lid and bottom all fit together. If you've got any questions or concerns go ahead and comment and I'll try to address them.