Thursday, 21 July 2011

Using builders bags (bulk bags) for composting

When clearing a garden or as in my case an allotment, builders bags can be very good for holding lots of waste top growth when left for a year or so rotting down quite nicely turning into a loam type soil.

Cold or Slow Composting
Let me say this process is not like traditional composting where the organic waste is turned over manually every few weeks. The bag is filled and completely left to its own devices for a long period, with nature doing all the work without our intervention.This process is known as cold composting as the waste does not build up heat as we see in the normal composting process.

Using builder bags for composting

Collecting Garden Waste

Collect all the garden waste you can and shove it all in as hard as you can into the builders bag making sure all four corners are compacted as you fill it up. Mix some soil and grass and even perennial weeds but avoid woody material as this takes ages to rot down, if ever. If you find a few garden worms chuck them in as well as they will have a perpetual feast and help in the composting process.

Please don't forget to make a comment or ask a question before you go 

Long row of builders bags for composting

Above you can see a row of builders bags filled with tons of garden waste composting away. The main problem with this is that are not exactly aesthetically pleasing making your garden or allotment appear as a building site. Most builders bags are in very bright colours so its is very difficult to miss them. Do what I didn't do and put them in a place where they are not so obvious.

The other thing is to make sure on the location of the filled bag as once it is full it becomes too heavy to move elsewhere.

Garden waste for composting in builders bags
The above image shows the typical garden waste that can be thrown into the builders bag. Basically it is anything and everything, except woody waste. It really will rot down over a year or so in the confines of the bag to be reused again and spread over your garden or allotment.

Covering builders bags for composting with carpet
Each bag I understand holds about a ton of soil and so far I have filled and emptied about ten bags. If you don't want weeds re-emerging from the top of the bag it's important to cover it with some old carpet or perhaps cardboard weighted down with a couple of bricks.

Comfrey growing in builders bags
One can grow plants in the top of the builders bag whilst the waste is rotting down. Above are comfrey plants feasting on the garden waste and below shows nettles gorging away in the same manner. Once established these plants can take care of themselves and suppress any weeds coming out the top.

Nettles growing in builders bags
Where can I get free builders bags ?

You certaintly can get them for free. Scout around your local neighbourhood, see if there is any building work going on. Nearly always there are empty bags laying outside empty or piled up on the inevitable skip ready to be taken away. Ask, always ask, the home owner or builder for permission to take them away. You are making good use of them, recycling them, and preventing them from landing up in landfill, for the time being at least. So far no one has refused me, I nice big smile goes a long way.

In the unlikely event that you can't find any locally or don't want to scrounge from other people you can buy

Garden waste transformed into useful soil  using builders bag

This is the final result of all that garden waste going into the builders bag after about 15 months. I have now spread this around on the allotment. There are still weed seeds in this mix and may appear quite soon after spreading but are easy to hoe back into the soil.

Garden Shop from

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