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Making your own peat free multi-purpose compost

Tony Callaghan 01/09/2022

Making your own peat free multi-purpose compost

First we need to cover some basic terminology!

Most readers will recognise that all homemade compost is going to be peat free.

Compost is a great soil improver, but compost is not the same as multi-purpose compost!  Multi-purpose compost is a poor description of what it is actually used for.

In fact multi-purpose compost should really be called 'growing media' as it is designed to work in place of soil when growing plants in containers, pots and raised beds. It is multi-purpose because it can also be added to soil as a soil improver. The thing that repeatedly catches gardeners out at the retail store is that the reverse is not true. 'Compost' on its own is a poor growing media. 

Terminology out of the way...

Multi-purpose composts have various items added to transform compost into an ideal growing media. We cover off the list of potential things in our blog How to make the best growing media.

So, how does the home user making traditional garden compost 'convert' this into a growing media?

Simple:  add about 15% by volume of the SoilFixer Biochar Compost Humification Agent to your compost pile as you add new organic material.

Is this cost-effective? 

We think so - the maths we worked out are as follows:

Bags of peat-free compost vary in price based on volume, type, and source (online/retail). Entry composts are 10 - 20p per litre and premium composts 50 - 80p per litre. 

The SoilFixer Compost Humification Agent (CHA) is £39.40 / 40 litre (20 Kg) sack. (We will round this to £40 to keep the maths simple)

A good growing media (potting compost, raised bed mix) and needs around 30% biochar in the final compost.**

Hence 40 litres of CHA mixed with 400 litres of organic waste at 15% volume will make 120 litres of biochar multi-purpose growing media.

£40 /120 litres = 32p/litre of biochar multi-purpose growing media.

Remember Biochar multi-purpose compost can be re-used year after year - just top up by adding 10-20% new compost. 

** Biochar does not decompose, but organic material reduces in volume as it decomposes.  So 15% biochar in the original mix becomes 30% in the final compost mix.

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