Design and Development of a Natural Draft Biomass Gasifier
R. Krishna Kumar February 28, 2009

Naturl Draft Gasifier - KumarNatural Draft Gasifier - Kumar


  • Operates under the principlle of “ Chimney Effectt ”
  • Natural draft caused by density difference


  • No blower is required for the operation
  • Automatically takes the required quantity of air for Gasification
  • Convey the Producer Gas formed by Gasification - Naturally
  • Reduced fuel consumption compared to traditional chulas

More detail, schematic pictures and testing information are in the attached pdfs and in the 2004 discussion:

This is an experiment using biomass in the KEROSENE WICK STOVE. (for more photographs) The stove was lit at the top using a little amount of biomass soaked in kerosene. The fine holes of 1 to 2 mm located all along the inner and outer frame are useful in achieving very good bluish flames. The flames continued for 30 to 45 minutes duration. Only at the end the performance was bad, the option was that, a lid was used to shut down safely. The fire was very high (Reasons I am not sure). If one does not have enough kerosene, and in emergency one can use the kerosene stoves too with fine wood shavings as fuel. The end product is very good biochar. I am thankful to TOM REED for explaining the functioning of a Kerosene stove, which was the motivation for doing this experiment.
Also see

This is the prototype of Magh series "Magh Utham Woodgas Burner". This is a natural draft burner (forced air is optional). Low cost, low weight, easy of operation, easy to collect the biochar by rotating the combustion frame and easy to reload it. As it is can be used for boilers / institutional stoves / domestic cooking / etc. The performance is good. There could be some more improvements in its design to increase its performance. For details and photographs see the link . The term "Utham" refers to "Best" which is part of the name of Prof. K. Purushotham Reddy a very well known environmentalist in India.

Magh CM-II natural draft woodgas stove, it is a very low-cost stove for heating and generating charcoal. It can also be described as a mini-charcoal making metal kiln. Instead of incinerating biomass generated from home gardens / any other dry combustible material generated as household waste usually throw into the garbage bins, can be used here. The leaf litter, dry twigs / sticks, chips of wood, wood shavings, etc., are very much suitable.

Envirofit and BP Stoves
Tom Reed,, August 29, 2008
Envirofit and BP StovesEnvirofit and BP Stoves

On Fri, Aug 29, 2008 at 6:38 AM, Thomas Reed wrote:
Dear Stovers:

I am attaching [the image above]that may be of interest to the stovers.

Here is an unsolicited commentary on our new XL WoodGas Stove, available at
Woodgas stoveWoodgas stove
along with our gasification books.

We have recently learned that BP is manufacturing a VERY similar stove
and selling them (only in India) in their equivalent of Walmart. I hear
they have already sold 100,000. Sounds like we are well on the way to
getting a "Billion Improved Stoves" out to the developing world.

If you cover the combustion air holes with aluminum flashing or sheet
metal screws the stove also makes a good gasifier.



MJA Biomass Gas Stove
Alexis Belonio, July 23, 2008
MJA Biomass Gas StoveMJA Biomass Gas Stove Burning Coal

Alexis Belonio writes (edited and annotated by Paul Anderson and Tom Miles):

Attached is a picture of my latest coal gasifier stove. This
is the same basic TLUD stove I have for wood charcoal and wood chunks.

For domestic use, I use carbonized coal (or coke) as fuel instead
of the raw coal. Coal can be used for the stove, but we don't want to promote
this as a fuel since it emits poisonous gas. I would prefer to use coal for
industry application where gas can be cleaned before it is released to the

I provide only a small amount of coal fuel in the gasifier stove, enough
for cooking. This mean that the power output is only small and the
metal I use is a stainless steel.

I ignite the carbonized coal by using a wood charcoal that has been soaked in
kerosene as igniter. [This is a TLUD stove, so ignition is at the top.]

[In the Belonio TLUDs, the fan only blows the primary air. The
secondary air is
pre-heated as it rises naturally between the fuel cylinder and the outer
cylinder, finally exiting into the rising flow of combustible gases.]
The smoke in the coal gasifier I have was eliminated [combusted] by mixing
preheated air with the gas generated from the reactor. I think
there is no need of [forced] mixing the secondary air by creating turbulence
with the combustible gases. Because in that case, you will need a
slightly bigger fan with enough pressure to push the air.
MJ Biomass Gas StoveMJ Biomass Gas Stove

Alexis Belonio

(little correction: i am a Hungarian born Hungarian citizen, and now living in Hungary again... )

When seeing the design from Haiti we were a bit afraid of using springs for ejection, so we really wanted to push from the bottom.. And that was a challenge with the spikes that make the holes.. And then my colleague had the great idea with the two-way lid. (He is called Attila, I include him in the list) And I dont think it should make much difference that the holes are rectangular.

The other great idea of his, which i am not sure if u can clearly see from the pictures, is that one of the lids is actually a tray that should slide under the briquettes after compressed (and pressed above the mould), and when you lower the jack, the briquettes just stay on the tray and can be moved (we will probably make another one of these, to save time like with the two mould sets with the legacy press). When we were testing the press, we had a little accident with the jack, so I am not 100% sure yet whether the tray will leave the briquettes intact(ish) but the first try when the jack was working was promising.

The fabricators are of a small coop from another very poor region of the country. (They are actually also Roma/Gypsy). A friend NGO set us up with them, and they were really great to work with.

Sure we would be very happy to make a manual out of this, but I first want to wait until we can properly test it and hopefully make a second prototype soon. The material costs were quite high which would be quite good to reduce.

I attach a collection of images and some info on presses that can be used as inspiration. (I think it would be really interesting to experiment with the screw press with the weights).

Thanks for your support!
All the best,

Nora Feldmar

File attachments: 


N. Sai Bhaskar Reddy,GEO GEOECOLOGY ENERGY ORGANISATION, December 30, 2007
Avan (Earth) StoveAvan (Earth) Stove
Avan (Earth) Stove has the features of both Rocket stove and Woodgas stove. It is made up of 25 nos of ordinary bricks, four bricks with slits, one piece of flat tile, one steel grate 7x7 inches and Clay mixed with cow dung. The approximate cost of construction is $ 2 (USD). All types of biomass can be used as fuel (Sticks / twigs / chips of wood / dry leaves / grass / saw dust / cow dung cakes / paddy husk etc.) and advantage of gravity is used for easy and semi-automatic feeding. Designed by Dr. N. Sai Bhaskar Reddy, GEO -Geoecology Energy Organisation declared as Creative Commons.

This is my recent TLUD stove design called 'Magh Smoke Burner Power Stove'


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