Vermicompost Construction

13 Aug

Today I return from a rather long break.

For the last month or so, I have been researching and designing a vermicopost system for Growing Lots Urban Farm in Minneapolis. Friday was We Built It day. This post will likely be the first of 2 blogs about the vermicompost construction because we didn’t finish today and so there are not pictures of the whole thing.

My first blog talked about compost and I want to talk about it again because I think it is one of the most interesting components of the food system. Organic material waste management is one of the biggest missing pieces in the food system. It is an industry particularly well suited for urban processing. Not only would this industry provide many good stable jobs for an area, but the end product is so useful. If the city composted even 10% of the organic waste stream the amount of compost produced would be enough to start and maintain dozens of urban farms on rooftops of warehouses and in old lots. Will Allen of Growing Power in Milwaukee said that their most important task is growing compost. With little soil or bad soil in cities, good compost is essential. With such a large potential supply of compost, urban farms would have access to cheap compost year round.

Back to the specifics of Vermicomposting. It is composting with the added management of worms. These worms help accelerate decomposition. Vermicompost is the highest quality compost. This makes it an essential fertility component to organic farmers who cannot use traditional fertilizers. It is not cheap, so Growing Lots wanted to build their own system.

I designed a system that allows Growing Lots to experiment with a couple different designs to see which parts would work best for an even bigger operation sometime in the future. The design is two 6 bin systems; each system with several tweaks. Bin system A is 2 by 3 bins. Each bin is made with panels are easily made and replaceable. Each panel is 3ft x 4ft, so each bin is 3x3x4ft. Each panel looks like this:


Each panel is a frame with hardware cloth in the middle. This allows the worms to pass through. This is one of the design variables. System A will have mesh panels, system B will have plywood panels. In system A, one of the 6 boxes will be filled with materials and the worms. As that box goes through its 3-4 month process, the box next to it will be slowly filled with materials. Then as the worms finish the materials in box 1 they will migrate through the screen to box 2 and begin eating that one. They will continue to do this circling through all 6 boxes.

In system B the panels will be plywood. In this method the box will be completely filled with materials and the worms added. After 3-4 months the worms will have finished all of the material and ready for a new box. In this system the worms are removed from the top. A piece of hardware cloth is placed on top of the pile with some juicy bit of food for the worms; something like rotten fruit. All the worms migrate above the mesh; then one can simply pick up the mesh and dump the worms in the next bin. The reason for this method it to ensure the worms finish all of the composted material before moving on to the next bin.

Construction will be completed this week and another post will follow up with photos of the final project.

Citywide compost would be one of the smartest and best investments for the City of Minneapolis. Instead of burning our brewery waste, we could grow food.


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