We are entering that time of year in which a lot of garden plants waste needs to be disposed of. It may also be a great time to produce a little biochar to fold into the soil.
We have learned that there is a strong likelihood that biochar will turn out to be superior to simply compost as a soil additive although our expectation is quite the opposite. The difference is simply that elemental carbon will hold soluble nutrients in place that are far too mobile when released from decomposing compost. Thus turning a charge of compostable plant waste into biochar should ultimately be a far superior practice.
There has been some observation that the initial soil reaction to receiving biochar is not as vigorous as initially expected but after one season this is overcome. This merely suggests that it may take a growing season to fully integrate the carbon with the soil biota.
The trick is a start a practice that can be easily repeated every year without a lot of fuss.
There we have learned that an open bottom drum will work fine. First a layer of branches less than an inch in diameter is laid down such that the edges are greater that the diameter of the drum. This permits air flow under the edge of the drum. Throw plant waste into the drum. This can be even accumulated over the summer as grass clippings and the like.
A metal lid is on top of the drum to prevent rain getting into the mass and accelerating composting. It should be possible to produce a well packed but not tightly packed charge that will still permit airflow.
When the time comes to fire the charge, I would first throw a layer of soil on top of the charge while leaving a ten inch hole in the center. The soil likely does not need to be there even but I would still put in three inches. I would then put in a charge of barbeque briquettes, preferably already burning into the center hole. This can be done with any other fuel of course but this way we are sure that the coals themselves will last for some time and avoid a premature failure. It may even be integrated with the weekly barbeque.
What is important is that the fire is strong enough and hot enough to sustain a top down burn. The beauty of this is that the volatiles coming off the burn front under the fire are forced to pass through the flame and produce even more heat as they burn. Tuned properly, and this surely will take a little practice, the process could be fairly smokeless. This could be famous last words of course, but I think that it is very possible although the initial ignition is sure to be anything but.
The lid is put back on but is left with enough of a gap to allow combustion gasses to escape. One could also mount a chimney on the top also.
This system is simple and with a bit of experimentations can surely be made very clean burning and satisfactory. Most importantly, it is easy to maintain and operate in a back yard, burn after burn.
Once the burn front has reached the branch floor of the drum, a water hose quickly douses the fire ending the burn. It is then easy to gather the charcoal and spread it onto appropriate beds and fold it into the soil.
Undoubtedly there will be superior well engineered solutions available over time as we establish a carbon making garden culture and promote the merits of the methods. In the meantime we have this as a working method and it should be possible to run it without smoking up the neighborhood and convincing the fire department that there is a disaster in play.
We have learned that there is a strong likelihood that biochar will turn out to be superior to simply compost as a soil additive although our expectation is quite the opposite. The difference is simply that elemental carbon will hold soluble nutrients in place that are far too mobile when released from decomposing compost. Thus turning a charge of compostable plant waste into biochar should ultimately be a far superior practice.
There has been some observation that the initial soil reaction to receiving biochar is not as vigorous as initially expected but after one season this is overcome. This merely suggests that it may take a growing season to fully integrate the carbon with the soil biota.
The trick is a start a practice that can be easily repeated every year without a lot of fuss.
There we have learned that an open bottom drum will work fine. First a layer of branches less than an inch in diameter is laid down such that the edges are greater that the diameter of the drum. This permits air flow under the edge of the drum. Throw plant waste into the drum. This can be even accumulated over the summer as grass clippings and the like.
A metal lid is on top of the drum to prevent rain getting into the mass and accelerating composting. It should be possible to produce a well packed but not tightly packed charge that will still permit airflow.
When the time comes to fire the charge, I would first throw a layer of soil on top of the charge while leaving a ten inch hole in the center. The soil likely does not need to be there even but I would still put in three inches. I would then put in a charge of barbeque briquettes, preferably already burning into the center hole. This can be done with any other fuel of course but this way we are sure that the coals themselves will last for some time and avoid a premature failure. It may even be integrated with the weekly barbeque.
What is important is that the fire is strong enough and hot enough to sustain a top down burn. The beauty of this is that the volatiles coming off the burn front under the fire are forced to pass through the flame and produce even more heat as they burn. Tuned properly, and this surely will take a little practice, the process could be fairly smokeless. This could be famous last words of course, but I think that it is very possible although the initial ignition is sure to be anything but.
The lid is put back on but is left with enough of a gap to allow combustion gasses to escape. One could also mount a chimney on the top also.
This system is simple and with a bit of experimentations can surely be made very clean burning and satisfactory. Most importantly, it is easy to maintain and operate in a back yard, burn after burn.
Once the burn front has reached the branch floor of the drum, a water hose quickly douses the fire ending the burn. It is then easy to gather the charcoal and spread it onto appropriate beds and fold it into the soil.
Undoubtedly there will be superior well engineered solutions available over time as we establish a carbon making garden culture and promote the merits of the methods. In the meantime we have this as a working method and it should be possible to run it without smoking up the neighborhood and convincing the fire department that there is a disaster in play.
