How to make and activate Biochar

Posted 11 Aug 2016

It’s easy – all you need is an old paint tin, some twigs, a willing fire, grass clippings and maybe a pot of wee – yes, really – wee!

What is Biochar and why make it?
Biochar is the result of wood that has been burnt with limited oxygen in the process known as pyrolysis. It occurs naturally and has been an intermittent part of soil profiles for millions of years. Unlike many other organic materials biochar has a long residual life and hence provides soil critters with a long-term home or habitat. Given time it is also porous enabling it to hold soil nutrients in the profile and its blocky nature also lends value to the structure of a soil. Biochar is a valuable constituent of a well-conditioned soil as it provides soil structure, critter habitat and nutrient storage.

Making Biochar…
Equipment needed
1 x Fire Drum and wood/matches etc. to make a fire in the drum
1 or more empty & clean tins with lids and maybe a handle (eg. paint tins), hammer and nail
Dry twigs/branches of a similar thickness
A steel post or fire proof rod
Method
Begin by lighting a fire in your fire drum. Next punch 4-6 holes in the lid of your tin with a nail. Fill the tin with dry twigs and seal with the lid. Use the steel post to hang the tin over the fire and leave for 20 – 40 minutes keeping the drum fire stoked as necessary. Carefully remove the tin. Let it cool for 15 minutes before examining the twigs (if you rush it the twigs will com-bust and turn to ash – this I found out the hard way). If the twigs are black and brittle all the way through then you have biochar if not they can be resealed and placed back over the fire.
Activating Biochar
The biochar that you have just made is inert and devoid of life hence you can add it to your garden like this and with time it critters will use it as their home and nutrients will be absorbed but why not hasten the process. Always dampen your biochar and smash it into smaller pieces with a hammer against a board as this will make activation happen more quickly. Here are a couple of ways;
1. Place your smashed biochar into a bucket, cover with worm tea and leave to soak for 1-2 months. Water into depleted garden areas.
2. Remove the bottom from a bucket and place it over soil in your garden, fill the bucket at least half way with biochar and top up to the brim with leaf mulch. Where ever, whenever possible use as an outdoor wee spot. Leave for a couple of months before removing the bucket and spreading around your garden.
3. Place your biochar in a bucket and add the same volume each of flour and green grass clippings. Mix thoroughly, cover and leave for 1-2 months before spreading around your garden.