David Field discusses large pile burns…
Following on from the article midyear 2020 here is an update on what has been happening since then.
During September and October I held 3 (4 hour long) workshops teaching a total of 21 people (mostly local) the basics of making biochar using a cone pit, 2 drum containers, a retort and a simple top lit stick stack…..pics below.
Everyone seemed to enjoy the workshops, which were very ‘Hands on” and gave some positive feedback. I know some of them are now actively making biochar in their own backyards. I felt it was important to also show how to crush, charge and apply the biochar into the soil.
Large pile burns
One of the workshop participants had a huge pile of Eucalyptus slash in her paddock and offered it up to turn into biochar as she wanted it out of the way and gone. So chatting to another biochar enthusiast we thought it would be a great experiment to scale up the small stack burn we did at the workshop (no pit or kontiki required). We spent a total of about 20 hours cutting and stacking the piles as tightly as we could, minimising the air gaps, and ended up with two piles about 5 x 5 x 2.5 metres high.
That gave us a harvest of 2 cubic metres of crushed biochar.
See photos below. Many thanks to Phil Stevens who came over from Ashhurst to help and share his expertise.
Reviewing the process we found that the harvest was way less than using a kontiki or cone pit for both the time it took and the return on the quantity of feedstock used. However we all had a lot of fun and engaged in interesting dialog as there were a few other people that came along to observe and learn.
Would I do it again or recommend giving it a try?
Yes…. but only if
1. The stack is already there just waiting to be burnt as a bonfire. I see many such stacks in paddocks driving around the countryside and it seems a waste that all that carbon goes back into the atmosphere as CO2 and other gases instead of (at least some of it) is captured and locked away in the earth.
2. That there is a ready supply of water available for quenching the fire and for safety.
Nothing until the total fire ban is lifted except cutting and drying feedstock.
Phil and I will be running a couple of biochar workshops in May for the Wellington /Horowhenua Tree Crops Assn members on the Kapiti Coast and in Upper Hutt.
Back here in the Wairarapa, Toby and I will be doing the same for a local Permaculture group in Autumn. Other workshops may follow if the interest is there.