the need for
aerobic composting
and how to do it

In the previous article on aerobic composting we covered some background information on plant nutrients and soil organisms. Here we will explain how it is done, based on the talk given by Marcé, a trained permaculturist.

Why the need for aerobic composting ?

Topsoil is being lost globally. So for remedial action fast composting would be ideal. Cold composting used in the garden when a compost pile is slowly added to, is a very slow process. Hot composting on the other hand is extremely fast. The heat also kills pathogens and seeds, keeping the weeds down where it is used. It may have further implications for the management of human waste, as the first article reveals.

how to keep it hot

According to Marcé, to maintain a temperature of 25-65 degrees, the C:N (Carbon:Nitrogen) ratio must be about 25-30:1.  The heap will reach around 65 degrees on about days 6-8, if you've got this right and will maintain a slightly lower heat once you start turning every 2nd day. The previous article explains what C, N and other elements are. N can be found in wet ingredients, C in dry grass and dry garden refuse like brown leaves. Thus roughly, build the compost heap with 1 green bucket green to 2 brown.  Very large material must be made small, with a shredder or by hand. Place sticks in the bottom layer to keep the bottom drained, and aerate. Pile it up to make a heap of about 1.5 meters. It has to be this big to maintain the internal heat. Start with a compost activator, if you wish. Urine is a good activator. After making the heap, every second day turn the outside of the heap inside. Good hot compost with the right C:N ratio doesn’t shrink a lot, and if it does it means there is too much N. To remedy add an ingredient like sawdust which is high in C when you fork over the heap.

turning the heap made frightfully easy

Stir the heap after two days. To do this, and make sure all material gets similar heat exposure, work around the heap with a pitch fork and remove the outer layer, and pile it in a heap. Use this as the core of the second heap you’re building, work inwards on the old heap, layering the centre of the old heap on the outside of the second, new heap. 

The right moisture content is also important. You have placed sticks at the bottom to ensure good drainage. To test the heap’s moisture, squeeze a lump of it in your hand. You must get only one drop or it is too wet and needs a central air-hole. If it is hot enough you can’t put your hand into the core. Check the moisture and temperature all the time for 6 days. White mold everywhere means it is too hot. If it is stinking, add sawdust or some material that is high in C. from day 10 – 18 just keep turning. You can google hot compost for more information.

There are three composting methods, vermicomosting, hot or aerobic composting and anaerobic composting for example Bokashi. You can see the info-graphic on the TUFCO page. Decomposition is very acidic in the beginning, and burns the roots of plants. So you can’t put raw compost on plants. Bokashi should also age for four weeks before you plant.

This sums up what I learned from Marcé, and it has introduced some fascinating questions and perspectives into my thinking on composting.



home page for more useful informationon eco friendly gardening


vegetable gardening the natural low cost way


gardening and where it all began


the other page on hot composting, nutrients and so on


easy composting: anaerobic composting


DIY rich organic garden fertilizer

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How to make good Compost.