I must admit to being a composting geek. I just love to see piles of what some would call ‘garden waste’ being turned into life giving compost. That is no exaggeration as we need compost to maintain and restore healthy productive soil.
There are many ways to make compost, I have used New Zealand bins for many years. The truth is that compost happens everywhere without human intervention. It is natural process of the breaking down of organic matter. Often the only thing that stops composting is the gardener.
The latest 3 bay NZ bins.
The key thing to remember that anything that has lived can be composted, including us! Just how it is done is open to much debate and the differences between methods can be reduced to how long it takes and the quality of the result.
Many gardeners have a heap of rotting stuff at the edge of the garden/allotment/files. They throw their ‘waste’ on it and just leave it. It will compost over time but there could be a lot of weed seeds and not much in the way of nutrients.
So, what is the best way to make compost? I would say there are two main criteria: Keep the contents dry as rain washes out the nutrients and slows the process. Secondly, have enough air going through the bin so that it heats up to around 60°C for at least 3-4 days. Making hot compost
Last week I found this US based site that shows a very specific way of making compost using the hot (thermophilic) method and then adding worms when the heap cools. The Johnson-Su bioreactor It takes around a year to complete the process, but the argument is that the longer time ensures a good supply of microorganism for the soil. PDF version (full details) And see this YouTube video
Full size bioreactors
The problem for most gardeners would be finding the large amount of materials to fill the heap. Even with a large ornamental garden I find it hard to fill the 1 cubic metre NZ bins. The Johnson-Su method would need almost twice that. Maybe the answer is a half-size version? It would certainly be much cheaper and easier to make than wooden bins.
The other issue is getting the right mix of ingredients. That is crucial for any type of composter to work correctly. Generally, it is described by mixing green and browns. That is, material high in nitrogen – greens with material high in carbon-browns. Ratio of greens and browns for best compost (Scroll down page.)