For prospective biochar producers finding the VUTHISA 3-DRUM BIOCHAR RETORT too expensive to build, the BLACK RIPPLE BIOCHAR KILN will be better priced and easier to operate especially for one-man operations.


The story behind the development of the original TRANS-PORTABLE KILN and later the VUTHISA 3-DRUM BIOCHAR RETORT is one of trial and error by global biochar enthusiasts. One such collaborator was an initiative called The Black Ripple, visit their website, which aims to reduce forest fuel buildup and habitat loss by producing biochar. Their kiln, still in operation since 2015, proved that a simple, low cost design, operated expertly, can yield long term results.

The Black Ripple proved that it is possible to produce biochar in a “flame cap” type burn over a relatively long period of time. NO NEED TO QUENCH WITH WATER (especially in remote areas), nor does it need a chimney to control the burn or an overhead hoist to remove the char. No air channels required – simply do an “open burn” similar to a Kontiki / cone type kiln. Lower the lid manually onto the kiln at a specified time to quench the flame. The result is a kiln that can deliver a controlled burn for many years and offer an affordable alternative for property owners doing the occasional burn to reduce their fire risk or to make small batches of biochar / charcoal. The kiln components can be transported by off-road truck and then carried by hand to the operational site and assembled with simple tools. It is also possible for ONE homesteader or individual to operate the kiln, do the assembly and disassembly, carry the panels and even place the lid onto the kiln without assistance. We propose a single perforated 55 gal drum be used (Method 2) and manipulated into position. Afterwards the charred contents can be rolled by hand to an awaiting pickup truck and transported for further processing. The whole kiln can eventually be disassembled (within minutes) and transported to the next operational area and re-assembled.

Biochar and char production methods have THREE problems to solve in order to be viable long term. ONE: We need to quench the flames TWO: We need to also make charcoal with the same process that is not quenched with water (Charcoal is sold by weight and should not contain more than 5% moisture). THREE: We need the process to be replicable for a long time by either doing it on the cheap or profitably with higher tech equipment. Black Ripple found a solution. A metal flame cap kiln with lid to quench or snuff out the flames and allowing char to cool over 12 hours. That solves problem ONE and TWO. If we want to solve the COST or AMORTISATION problem, one has to insulate the kiln especially if used frequently. High initial cost ($225 for vermiculite or $1500 for fiber plaster insulation applied onto the hot face 20 to 30mm thick), but profitable in the long term as you increase longevity.

Feedback received from clients in the USA revealed that fabricators deemed the process of “cold rolling” sheets to achieve that very specific “arc” of the circle to make up a ring kiln – too labor intensive and expensive. Hence our decision to adopt a pentagonal design. A single panel bent out at a 72° angle is easier to mass produce with a simple tool shop bending machine. It will be easier to flat pack the panels for transport to site as well prior to assembly into its current PENTA shape. However we have plans for a RING KILN consisting of 4 panels for those with the capability to shape the curved sides.

Ring Kiln

The kiln will be called the Black Ripple Biochar Kiln in recognition of their efforts, to be operated in one of two modes:

1) Controlled “open burn”
2) At a specific point in the burn, cap the kiln via the lid, and seal with mud and allow contents to “cook”
3) Following cool-down, unbolt a side panel to remove the char by means of a shovel

1) Remove one of the panels
2) Place or wheel via a drum lift a single 55 gal drum, with holes punched into the sides, into the center of the kiln and fill with feedstock and replace the “full curl lid” and clamp onto the drum – replace panel
3) Fill firewood around the 55 gal drum and top light – DO NOT PLACE LID
4) Flames will heat the contents of the 55 gal drum and gas off into the larger kiln shape
5) As soon as the gas in the 55 gal drum has vented fully, close the lid and seal with mud
6) Following cool-down, unbolt a side panel to remove the 55 gal drum and remove biochar

The PDF manual below will demonstrate how to construct, assemble and operate the pentagonal shaped- and ring kiln. Only basic shop tools are required, but CAD plans (including digital DWG files) are available, compatible with laser-cutting equipment. The manual includes detailed drawings for both the PENTA and RING kilns and measurements are in inches and millimeters.


The original published instructions for the TRANS-PORTABLE KILN kiln was to build a small fire, then set the kiln over it with four air channels below the kiln, set into the dirt, before adding more fuel. The air channels are then backfilled with dirt when ashes appear in them.

The folks at The Black Ripple were able to increase longevity of the kiln by not utilizing air inlet channels to provide primary oxygen to the flames. The kiln was completely filled to the top and top-lit. Others like Kelpie Wilson teaches people to use her Ring of Fire kiln in this same manner. One can let the fire front nearly reach the bottom of the kiln before adding more material, just to ensure that the fuel gets completely pyrolyzed, but Kelpie does not and she doesn’t have any incompletely burned material. A fair amount of experimentation and practice will be required to get optimal results. Closing the lid too soon may cause incomplete pyrolysis and a high degree of torrefied wood. Prolonging the open burn phase may produce a high degree of ash.

Making charcoal and biochar in a conventional manner

In order to get more consistent results and to increase longevity we advocate using a single 55 gal drum positioned in the middle of the outer metal vessel (panels bolted together) and insulating the lid and panels on the inside with fibre plaster or vermiculite and kaowool.

Ceramic Fibre Blanket consists of separate strands of fibre, and in a turbulent gas environment it falls apart. The problem is solved by adding a layer of either Fibre Plaster or Vermiculite on the inside. Fibre plaster is excellent at eliminating shock, onto the flame impingement area. The commonest attachment used for Fibre Plaster onto steelwork is expanded metal. The expanded metal is tacked onto the shell (5mm away from the surface, by bending down the end strands) and the Fibre Plaster is smeared through it, to the preferred thickness required (usually 30 mm). Mentex 72, similar to what is used in plastering walls is the preferred grade. Flattex does not work. Simply apply with rubber gloves.

The second method and cheapest by far is using Vermiculite. In South Africa we have a specialist Vermiculite supplier and visually it does not look like vermiculite. Vermiculite is only 15% of the cost of Fibre Plaster and is glued on – no expanded metal required.

Fibre plaster or Vermiculite insulation attached to inner surfaces of panels and lid – kaowool can also be used in the lid to bring down the weight

Reinforcing plates are first spot welded onto the inside of the panels to protect it from impacts and ensure that the 5 SIDED shaped flange welded to the underside of the lid will insert properly. At the start of the burn, line up the removable panel carefully, vertically and horizontally, to help minimize air leaks. Panels have slotted notches to allow easy removal and attachment of panels. Many fabricators in USA prefer bending flat panels as opposed to cold rolling panels to form a perfect circle, but as mentioned we also have detailed CAD plans for a RING kiln design as well.

To remove char – a single panel is unbolted and removed at the end of the cool down period (12 hours) with a socket wrench / battery powered compound impact wrench – and the char is shoveled out or if 55 gal drum is used, the drum is removed and biochar extracted from it.

Making biochar with the use of a single 55 gal drum

These YouTube video shows similar systems in use – for demonstration purposes:

Biochar is carbon-rich, porous material made from heating wood or other plant material in an oxygen-deprived atmosphere through a process termed pyrolysis. As a soil additive, biochar offers numerous potential benefits. Those benefits include increased moisture retention, reduction in soil acidity, improved air permeability, elevated cation exchange capacity, increased soluble organic carbon, synergistic interactions with soil microbial populations, a reduction in fertilizer use and irrigation requirements and carbon to mitigate climate change.
The bulk of pyrolysis and carbonization reactions occur in the temperature range from about 200°C (392°F) to 600°C (1112°F). One can think of pyrolysis and carbonization as simultaneous physical-chemical processes, changing the biomass into pyrolytic gases and char. At sufficient temperatures, generally above 300°C (572°F), carbonization modifies the chemical bonds within the remaining solids such that it is less likely to be consumed as food by living systems. The 350°C char have a much lower adsorption capacity than the 600°C char. It is advisable to purchase a Type K thermocouple and insert it through a 5mm (0.19685 inch) hole drilled in one of the panels to check temperature from time to time.

Please consider joining our Portable Kiln Google Group for further support:

The Black Ripple (USA) and BKI (SOUTH AFRICA) will soon price fabrication in both countries, so watch this space. Anyone interested in ordering a BLACK RIPPLE kiln or the plans please fill in this form here or fill out the embedded form below:


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