How they work, why they work and the benefits over other cook stoves:
Wisdom Stoves and our Kenyan partner, Wisdom Innovations, are proud to be able to offer two unique cookstove models to Kenyan families. Both provide life-changing, long-term health and financial benefits.
Nathan Puffer, co-founder of Wisdom Stoves and Wisdom Innovations, has been actively researching gasification stoves since 2009. He has designed nearly 20 fan assisted and naturally aspirated stoves over the years in order to create cookstoves that address the needs of the Kenyan people and best use available fuel sources.
In 2012, Wisdom Stoves’ Kenyan partner and benefactor, Wisdom Innovations, started manufacturing and distributing our first cookstove model called the “Malaika Jiko,” or “MJ.” A year later, the second model, the “M2,” was ready for our customers and community partners.
The MJ and M2 are top lit up-draft gasification cookstoves, or “TLUDs,” and are innovative variations of the Tchar stove. Both cookstoves are designed to burn biomass including wood, corn husks, cow dung, coffee husks, dried bio mass briquette, and other, as of yet unidentified fuels. To learn more about Tchar and TLUD stoves, visit Drtlud.com.
The MJ is placed on top of a 10” traditional improved Kenya jiko with a ceramic insert. Make sure the fit is snug and secure. Doors on the two stoves should be aligned and open.
The M2 works independently, as the design includes a ceramic insert.
The ideal wood is dry and broken into matchbox-sized pieces. It is common to see Kenyan residents using sticks about 8” long bundled together and placed vertically into the fire chamber. All of the wood used, including the starter wood, should be as dry as possible. Proper wood preparation is important, as green or wet wood will increase the possibility of a smokey start.
Load the wood to just below the secondary air holes (4” below the top of the fire chamber). On top of the biomass used, place starter wood (smaller pieces). This starter wood may be rinsed in kerosene or paraffin. (The kerosene is only used when an accelerant is needed to start the fire.) It is advantageous to have slightly larger, thicker pieces of wood below the smaller, thinner ones.
Light the sticks on top of the cookstove. The goal is to light the entire surface at the top of the fire chamber (see why do we light the stove at the top?).
A pot/pan can be placed on the flame as soon as the stove is lit. There should be minimal amounts of smoke (see Why doesn’t the stove smoke?). Cooking time is approximately 45 minutes at a high temperature when using wood like blue gum eucalyptus (see How do I adjust the stove?). Cooking time may be extended by adding small amounts of wood and making sure they are below the secondary air holes (4” below the top of the fire chamber).
Gasification can be thought of as drawing smoke through a hot bed of char where chemical reactions take place. In that oxygen starved location, one oxygen atom is removed from both the CO2 (carbon dioxide) and the H2O, reducing them to CO (carbon monoxide) and H2 (hydrogen). When the gases reach the secondary air holes (the circle of holes 4” from the top of the fire chamber), these gases are burned, having left an oxygen deprived zone and entered the oxygen rich secondary air combustion zone.
When first placing a cold pot/pan on top of an MJ or M2, the flames may be snuffed out if there is not enough heat to combust. In this case, smoke and soot may be produced. As the pot/pan heats up, more heat is retained by the bottom of the pan and there will be less smoke and soot. The reason for the flames’ reach above the fire chamber is that there is not enough oxygen being supplied to burn all the available gases. The flames are searching for oxygen.
When the flame changes from an orange/yellow/light blue to a deep blue, the bio mass has been turned into charcoal (see How does the stove produce charcoal while I cook?). If using an MJ, lift the cookstove from the traditional improved jiko, and the lit charcoal will fall neatly into the jiko and continue to burn. At this point, cooking or warming can continue, or the charcoal can be preserved by being placed in water or in a snuff box. Another alternative is to use the charcoal as a bio char to augment the soil. (See What is bio char?) If using an M2, carefully lift and turn over the cookstove so that the charcoal empties from the enclosed ceramic insert into a jiko or another safe receptacle.
The goal is to create a hot bed of char that will heat the wood below. This causes the lower layer of wood to release the producer gas in the wood. The process in which the gas is created is called “pyrolysis.” The reason why it is important to have hot coals across the top area is so that the smoke and gases pass through the hot char.
The door on the traditional improved jiko provides the air that comes up through the biomass in the fire chamber and out the top of the stove. This is referred to as the “primary air.” The primary air provides enough air for limitedcombustion of the bio mass/wood.
The door on the MJ cookstove provides the air between the outside shell and the fire chamber, until the air exits through the secondary air holes (located 4” below the top of the fire chamber). This is referred to as “secondary air.” Secondary air provides oxygen and heat from the burning char in order to burn the gases that are released.
We recommend adjusting the primary air (traditional improved jiko door) and not the secondary air (MJ door). By reducing the amount of primary air entering the stove, less gas will be produced, giving the secondary air supply a chance to fully combust the gases. As experience increases, the stove can be regulated, keeping a balance between the oxygen, heat and fuel for desired effect.
Initially, the hot char is drying the wood. After the wood gases pass through the hot char and enter the secondary air zone, they are introduced to enough oxygen to combust. The process continues uninterrupted to the bottom of the stove, burning top to bottom. The descending pyrolytic front leaves charcoal in its wake.
Bio char is a name for charcoal when it is used as a soil amendment. Added to the soil, it sequesters carbon. Instead of carbon being released into the atmosphere, as it is in the process of burning, the carbon is stored in the charcoal. The benefits of using bio car include improved water retention, reduction of nutrient leaching, reduction of soil acidity and the reduction of irrigation and fertilizer requirements.
• Eliminates wait time for cooking
• Allows cooking and production of charcoal to take place at the same time
• Burns all carbon monoxide, hydrogen and small amounts of methane that are produced
• Produces just the right amount of charcoal to fill the traditional improved jiko
• Greatly reduces destruction of wood growth compared with current methods of charcoal production
• Greatly reduces harmful smoke
• Creates significant cost savings (1 sack of charcoal in Ksh = cost of one MJ)
• Increases awareness of conservation efforts in the areas of forestation, indoor air pollution, water resources and erosion
• Allows families to save money on fuel (biomass vs. charcoal, kerosene or propane)
To learn more about our unique cookstoves, click the link to read the user manuals.