This is a co-creation project that is both open source and open knowledge. It is based on work first done by Amanda Ravenhill & Hugh McLaughlin at CHAB Camp in 2010.
In terms of the quality and quantity of biochar, and the cleanliness of the stack gases, this design is yielding the best balanced results I have yet achieved from a TLUD made from small tin cans. The heat output is also quite considerable.
Warning: You may only use this design at your own risk and if you agree to assume 100% responsibility and liability for all consequences, intended or unintended. The Love iCan must ONLY be operated in a well ventilated area that is fire safe. A bucket of water and a first aid kit must always be present and conveniently at hand. If these terms and conditions are unacceptable, please do not try this project. If you do proceed with this project, you acknowledge that you have read and accepted all warnings, terms and conditions in this document.
The three cans above are the “core” of the design.
Each can as a specific function. From the top, they are:
Top can: Draft. This can simply has both top and bottom removed.
Middle can: Combustion of biogas produced by pyrolysis. Note the secondary air holes in this can. There are three sets of 6 holes evenly spaced around the can. The number, size and layout of the secondary air holes is worth experimenting with.
Bottom can: Pyrolysis of biomass — TLUD. I fill this can with wood pellets to the top of the ribs in the side of the can. I then remove a portion to soak in 91% rubbing alcohol for 4 or 5 minutes in order to create the pyrolysis starter. I wait about 5 minutes after igniting the starter on top of the fuel in the pyrolysis can before I add the top two cans to the system. This allows a robust pyrolysis zone to get established. Once the pyrolytic gases enter the combustion can, it will generally be necessary to ignite them as well. Run times in a Love iCan made from a 15 oz. can are generally around 50 minutes, +/- 2 minutes. Longer run times are apt to be too cool for clean results. A very good run will end with small, deep blue, jets of flame above the gas ports. It will then self-extinguish with no smoke. Note: The optimal run time will vary with each feedstock type used.
WARNING: The Pyrolysis can will be EXTREMELY HOT at the end of a burn. It will be full of very hot charcoal. It should only be handled with well insulated gloves and pliers. Please be aware and warned that the Combustion can, the Draft can, and the Safety can will also get very hot and must never be touched with bare hands. The Love iCan should ONLY be operated in a well ventilated area that is fire safe.
In operation, as can be seen in the Easy iCan document, this set of cans would be placed inside a windshield / safety can. They would be set on angle irons used as spacers. The spacers create the gap which allows the primary air to enter the system via the holes in the bottom of the pyrolysis can. It is interesting to vary the height of this gap to see what happens. How small a gap will work? Note: If a tall pineapple juice can is used for the safety can, as is suggested in the Easy iCan document, the best results will be had if the top is removed, but NO other holes are made in the can. This will pre-heat the primary and secondary air flows. Pre-heated primary appears to make a significant difference.
Gas ports in the bottom of the Combustion can.
This shows the bottom of the middle can, or the combustion can. In the past, I have usually completely remove the bottom of this can. The insight Ravenhill and McLaughlin had was that, rather than a can with no bottom or one with a large central hole, it would be better to separate the pyrolysis from the combustion as much as possible. Further, these ports insure that the biogas will enter the combustion can with some velocity. This helps to generate good turbulence which is essential for clean and complete combustion of the biogas.
I observe further benefits of this approach.
1. This is a much more secure barrier to any oxygen entering the pyrolysis can from the top. Evidence of this is the almost total lack of ash that can be seen at the end of a run. If the biochar is quenched in water, the water will be completely clear and will not show any trace of cloudiness caused by ash.
2. The size of the gas ports determines the rate of pyrolysis very nicely – regardless of the size of the primary air holes — as long as they are of a reasonable size. That is, the size of the primary air holes is no longer a critical aspect for tuning the system. If the gas ports are too small, the pyrolysis will either fail entirely or will be so slow and cool that the run times will be excessive and there will be clear evidence of creosote formation. If the gas ports are overly large, the run time will be short and the biochar harvest inefficient.
3. The net result of this design is a hybrid: part natural draft TLUD and part retort. It has no moving parts. It is, none the less, very effective.
Those familiar with the Easy iCan will note that the Love iCan uses the same layout and number of holes for the gas ports as are used for the primary air supply in the Easy iCan. In fact, exactly the same design for both the primary air and the gas ports can be used. The size of the gas port holes will, however, be larger than the primary air holes as described in the Easy iCan document.
On the left: Primary air in the bottom of the Pyrolysis can. On the right: Gas ports in the bottom of the Combustion can.
For further practical guidance on operating the Love iCan and for making biochar, as well as activities for using the biochar, please see The Biochar Activity Kit. The kit file Making Biochar - PDF will be of especial interest.
Warning: You may only use this design at your own risk and you agree to assume 100% responsibility and liability for all consequences, intended or unintended. The Love iCan must ONLY be operated in a well ventilated area that is fire safe. A bucket of water and a first aid kit must always be present and conveniently at hand. If these terms and conditions are unacceptable, please do not try this project. If you do proceed with this project, you acknowledge that you have read and accepted all warnings, terms and conditions in this document.
The Love iCan is free to use.