Making your own peat-free compost with BioChar

The best way to use BioChar in our soils here in the UK and Europe, is to use what is often called “activated” BioChar.  There are many definitions of what this means; BioChar needs to interact with decomposing matter to create microbial oxidisation which then, thanks to the large surface area of BioChar, allows every crevice to hold on to vital nutrients. The easiest way to activate BioChar is to add it to your compost heap, allowing the nutrients from the surrounding waste to be absorbed over the composting period.  The result is wonderful, high nutrient, peat-free compost, with activated BioChar as part of it’s structure.

There has been a good deal of research done (and it continues) on which soils benefit the most from the addition of BioChar; most seem to agree that the soils of the tropics benefit when any time of charcoal-burned matter is added, whether activated or not.  This is due to the very poor quality of these soils, and the benefits included better water retention, raising of the Ph of the soil, better aeration and better nutrient retention.  However, in the European soils, which have a very different structure, much higher in hummus, the impact of these benefits is much lower.  Researchers have found that pre-activated BioChar provides a dramatic impact however, when it is first activated, thus becoming a natural replacement for products like vermiculite and also impacts the rate at which added foods are released.

As we all become more aware of our impact on the environment, it makes sense to embrace these findings and make our own compost (peat-free) and use up a large amount of our waste into the bargain – which means it won’t be going to landfill.

The first thing is to be clear about what can and cannot go into a compost bin:

YES: waste vegetables – raw or cooked can all go in.

NO: waste meat and fish – no. never. These can only be composted using a method specifically designed for these products.  The Japanese have had a superb method for years, called Bokashi.  There is an interesting article on how this works in The Guardian.

YES: Cardboard (not shiny coated though) and newspaper (not magazines)

NO: Clothing made of artificial fibres. They will not break down.

YES: Wool and coir string.  Even John’s old wool socks went in last year – ripped up first – and they seem to have been appreciated by the courgettes!

NO: Cooked eggs. Yucky smell!

YES: Raw eggs. Even in their shells if past their best.  These will add amazing sulphur smell, but they’re worth it and if you put an egg, still in the shell, under tomatoes before transplanting, you’ll be amazed by the growth.

NO: Grass cuttings.  These are not a good addition, despite many people adding them to their compost.  There is no real value from grass and they take a very, very long time to decompose.  The best thing to do with the grass waste? Biochar it, of course!

YES: Leaf matter and general garden waste.  The compost heap loves gardeners, so add almost everything (except the grass) that you cut back, pull up or rake in your garden.

Then you have to decide where to put your compost heap.  Don’t let having a small garden stop you here, we had one of these portable compost bins in our courtyard garden in London for years, and it takes very little room.  If you are lucky enough to have a larger outdoor space, do consider making a compost area, pallets work well for these, allowing for two large piles of compost which you can easily turn and alternate between.  Do remember, wherever you put it, that the smell can be a bit rich, especially if we get sunshine, and it will also attract insects.

To create the peat-free compost, we recommend that around 15-20% of the total mix should be BioChar.  We add a coal shovel full to each wheelbarrow we add to our own compost heap and this mix has worked well. If you are using a sealed compost bin, don’t worry that you cannot turn the compost, this is not needed when created in the sealed environment.  However, we did find that this type of compost required a little more of the BioChar to get a really good texture, so we recommend a thin layer be added, around 2.5cm-4cm thick, every 50cm.

Compost you make this year will do a lot of decomposing over the winter months.  It will be ready to use, in your garden or hanging baskets, by next spring.  In addition to doing your bit for the environment, you’ll discover that the addition of the BioChar means you need to add far less chemical fertilisers to your crops and that you can water them less often. The best news of all?  You took you waste and turned it into peat-free, carbon-locking compost!

We’d love to know how you get on.  Do share your composting stories!


Dinah and John





References: See the report “55 uses for biochar” here for the referenced information in this article.

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