Hot Composting Bin

Thanks to some pretty wasteful (and useless) builders I had a couple of sheets of tatty 75mm thick Kingspan insulation left over from a recent extension along with a load of black plastic sheeting. I've wanted a hot composting bin for a few years but couldn't justify spending £200 on a compost bin!!

Firstly I measured up an existing wheelie bin to get approx dimensions then rounded up to make the cutting and measurements easier. The end result is a little bit bigger than a regular wheelie bin.

Rigid thermal insulation board.

Plastic sheeting

Large threaded screws

Grab adhesive

Spray adhesive.

I was a little slack with photos - sorry!

1) Once you have decided on your dimensions, cut your front, back and sides. Cutting is still messy even with these boards. The boards can be easily cut by hand but for a straighter cut I used a circular saw with the flexible attachment to my vacuum cleaner on the outlet of the saw - do not cut with a power saw without doing this as the dust is fine and horrible and will go everywhere! Cut the last bit with a hand saw if your blade doesn't go deep enough.

2) Don't forget to cut a chunk off the bottom of your front panel for access. Allow around 30 to 40cm or whatever you think you can comfortably get a spade in. My box is upside down in the photos at this point.

3) I tried a few methods before hand as to the best way to put the boards together. I tried various screws and wall plug combinations which a) didn't work and b)would've been very difficult to get the screw through one board and into the wall plug behind it.

I found a large threaded timber screw that seemed to have enough bite when screwed through to pinch and hold two boards together. The fatter the thread, the better. DO NOT overtighten this though, as you will just spin the screw in the insulation board and strip whatever it had managed to grip. You should be able to screw in tight enough that the head of the screw indents and goes flush with the board. Don't be too rough though as they can pull out with moderate effort. I also used a tube of grab adhesive (Gorilla glue in this case - £11.23 from Amazon) to really help the bond. I probably went overboard and used a whole tube for the entire build.

I had to buy more screws especially for the build unfortunately (£19.50 from Amazon). I used these generously, about 4 or 5 down each side to join to the next board with a liberal helping of grab adhesive too.

4) Once your front, back and sides are on, measure up and cut your base to fit and same again for the lid. Attach the base as per the above with plenty of large thread screws and adhesive. Leave the lid off for now.

5) The box should be pretty solid at this point. I didn't wait for the adhesive to set and cracked straight on.

6) Now the faffy bit - and there may be better ways to do this. Wrap the box with the plastic sheet like a large present. I did this for the aesthetics and to keep rain out and protect the inside from moisture and later disturbance/digging. Try to have over laps such that if moisture drips down it goes over rather than under the sheet beneath.

I used a load of spray adhesive (3 cans for £12.25 from Amazon), again I may have gone overboard and used more than necessary, to get the sheet to stick nicely to the panels. Doing the outside of the box was way easier than the inside which I lined one side at a time. In the base, before lining, I chiselled a slot for some perforated plastic pipe to go in to act as leachate drainage. Base was then lined and the pipe glued into place in the slot. 7) Wrap the lid and front hatch. The front hatch should push in snuggly. I used a ratchet strap to hold it in firmly when the bin is filled. 8) Hinge for the lid (optional as you could just put a brick on top). I used two bits of scrap wood, a couple of hinges I had lying around, and the big timber screws again and grab adhesive to stick the bits of wood to the lid and bin. Drill holes through the wood first. Mind you don't do what I did. The screws are long and need to go into the sides of the bin, not straight through the 75mm panel. Screws on the bin therefore need to be at the edges. I put mine in at 45° as the pilot holes weren't close enough to the edge and i'd already glue it and fixed the top bit of the hinge. Seems to be fine! Job done for less than £45 in bits I actually had to buy!