Graduation Day
Mahbubul Islam
The "Akha" Top-Lit Updraft (TLUD) Gasifier Cookstove
Milita Mardi-Fazilpur, Pinky Rani Halder, China Halder and their stoves
Mahbubul Islam
Artisans making Akha components
Mahbubul Islam
A TLUD is a simple gasifier that is composed of a vertical tube that is filled with small pieces of wood, or densified biomass like pellets, balls or small briquettes. This is called a 'fuel bed.' It is ignited at the top, and underfed with primary air from a grate at the bottom. The ignition front travels down through the fuel by radiating heat into the raw fuel, drying it, and initiating pyrolysis. Released volatiles are ignited by the flame. The reaction is sometimes called a “migratory flaming pyrolytic front” (MFPF). Residual char is left on top of the fuel bed as the MFPF moves down.
The burning volatiles create an orange gas flame for cooking. Once pyrolysis is completed, the orange flame goes out, and the left-over char is colleded and smothered, or quenched with water.
We needed the "Akha," a culturally-appropriate TLUD for Bangladesh. It had to be made locally, study, and made with with as little (imported) metal as possible. Because of its heavy construction, it has a hinged grate for removing the char. To protect the Akha for free use, an there is an open-access patent. The current version of the Akha is a prototype being evaluated for acceptance, and obvious improvements can be made.
For the Akha to be successful, it has to:
- have very low emissions of smoke
- be easy to operate and burn reliably without going out
- make char for use as biochar or as charcoal.
- burn less fuel than a traditional stove (even when the char is unburned)
Making char may be the critical enabling feature for Akha acceptance.
The main lesson learned was that the Akha was well accepted by the women who were well trained in its use. We already knew the main limitations of a TLUD:
- It does not burn loose biomass, so traditional stoves will be saved for that purpose.
- It takes time to size woody fuel into small pieces, however, producing fuel for TLUDs may become some's livilhood.
- It does not burn wet fuel.
- It is batch-loaded with fuel rather than continuously stoked, to for long cooking times it will have to br reloaded.
- Women have to the trained on how to prepare fuel, and operate a TLUD.