Biochar stats of 9 loads of biochar we made and crushed for a client. Unfortunately, it rained before the 9th load completed, so we ended up with 1.8 cubic yards instead of 2. Part of my grant followup is providing data behind our production of biochar. So I took lots of pictures and filled out a spreadsheet.
The feed stock was dead and down hardwood from around our farm, mostly elm and cottonwood. Most had an average of 6% moisture, with a couple loads of larger material 12-16%.
Each load was weighed with a crane scale as it was loaded into the retort. Weight did not include the kindling or tank half.
Fire started on top of the load in the style of an Oregon Kiln or Flame Top Kiln, where the fire on top burns the smoke and noxious chemicals released from below. Little smoke is released.
When the heat in the burn was over 1400 degrees F and volume of feed stock had shrunk, we closed the lids and monitored the temperature, as the syngas piped into the fire box kept the heat from dropping too fast.
When the syngas stopped and temperature was below 500 degrees, a misting spray was put in the inner tank from the access points on both ends. The access points double as the temperature port and piping the syngas into the fire box.
An average of 3 gallons of water was sprayed into the tank with the temperature monitored periodically. When the temp did not drop between two spraying events, the ends were resealed and the load left to cool, usually over night but a few loads cooled for approximately five hours before unloading.
The loads were also weighed when it was lifted out, and before dumping on the sorting table. On the sorting table pieces were pulled if the were only partially burned, and the rest was placed in 55 gallon drums.
When needed, we can crush the biochar. We repurposed a grain drum roller, spread the drums apart so we didn’t make all dust. The average size is less than 1/2″ in 3 directions. Client was pleased with the size. Have a sifter set up if needed just to separate large chunks out but not crush it all.
Now modifications and efficiencies are to be made (not in any order)
- improve insulation.
- mist system inside inner lid
- open/closing system for 1 person operation
- complete trailer
- get scale into pounds
- get temp probe to record like it’s suppose to.
- splitter / hydraulic chop saw for processing feed stock and fuel
- lifting / rotating arm for loading inner tank into outer tank so crane truck not needed
- conveyor belt / paddle auger to move biochar
- bulk tank for storage
- oh so many things
Next investigation is starting with wood chips, as looks to be less handling of feed stock.[The retort is a 300 gallon tank inside a 500 gallon tank. The upper lids are nested with spacers, and hinged. A 55 gallon barrel is attached on one end as the fuel box. Pipe comes from the inner barrel into the fuel box for the syngas to be utilized during the burn. Hooks on both ends around the port pipes are used for lifting the tank in and out.]