Rebuild
My system is open source. I want to encourage everybody to copy this system and start producing soil in the city. In order to spread this system easily I have developed it as cheap as possible. Of course you can use also higher quality materials. In case a composting bucket will be created or adapted based on my system and sold on a commercial base – I ask as my share to get one percent of the final price of each sold unit.

Costs
As DIY you can build this composter for about 12 Euro (in Germany, this might vary in other countries). In case you don't have the time I can offer to build one for you and send it to your address on a donation base. Just send me an Email to info <at> subrealic.net! Please have in mind that that I would have to spend quiet some time and work. I will prioritize the order of requests on what my work is worth to you.

Tools
1 mm drill for setting the air holes in the lid (drill or nail the holes from the outside towards the inside, I made myself a small tool with spikes, see image below)
Scissors or knife to open the bag
Sewing tool or rivet setter to attach edge reinforcement and click closures to the openings of the sand bag


Use
Feed from upper side, harvest from the lower side.
Start slow. System has to find its own balance. Two thirds should be soil. Don't add potato peel, citrus peels and pumpkin seeds. Don't let the excess water reach the bag, remove it, mix with water and use it as fertilizer for your plants.
One bucket this size can only process a part of one person's organic waste but will produce enough fresh compost for all plants in the apartment & balcony.