I saw people talking about making use out of invasive plants and I have something to share here.
I recently used the "top lit open brush" method as showed in Skillcult's video to turn a pile of invasives into biochar. Here is the link, he talked about the pros and cons.
The pile was 6 ft tall, about equally wide at the bottom, mainly made of Japanese honeysuckles with some wild roses and thorny blackberries. I lit it up on the top and it only took less than 10 minutes to burn to the ground. Flaming shooting out of the center probably reached 15 ft tall with no visible smoke. I guess it was an indication that the volatile organic compounds were gassing off quickly and completly combusted.
When there was no more flame, I doused the pile with water to stop it from burning down to ash. I got 10 gallons of charred sticks this way with very little ash. now the chars are being soaked in compost tea before mixing into the compost pile.
I feel this method is particularly suited for burning large pile of small sticks and vines. Make the pile more vertical than cone shaped and burn it top down. That make a big difference of how much is converted to char rather than ash.
Thanks for reading and welcome to share your experience. Happy burning!