Top-lit updraft gasifier
A Natural Draft Top-lit gasifier (ND TLUD) is a micro-kiln used to produce charcoal, especially biochar, and heat for cooking. A TLUD pyrolyzes organic material, including wood or manure, and uses a reburner to eliminate volatile byproducts of pyrolization. The process leaves mostly carbon as a residue, which can be incorporated into soil to create terra preta.
Dr Thomas B Reed and the Norwegian architect Paal Wendelbo  are considered to be the first ones to have come up with the working idea of a Natural Draft ND TLUD gasifier.
A ND TLUD gasifier takes it further from a rocket stove in more efficient way of smoke free - highly efficient combustion of the fuel.
A TLUD gasifier stove  is commonly constructed with two cylindrical containers the inner fuel pot has holes in base to serve as primary air inlet and holes like skirt on the neck serving as secondary air inlet. The outer cylinder takes air from its bottom (lower of sides) which can be natural air draft or forced with a DC fan depending on requirement and construction model. Any biomass (with less than 20% water content) can be used as fuel, filled up to the neck where the secondary air inlet holes start. Initially, the top layer of the fuel is ignited with starters for the pyrolysis to start. Upon the start of the process, air enters via primary and secondary air inlets: the primary inlet helps in the upward draft lifting of the pyrolysed wood gas and the secondary inlet above the fuel layer helps in ignition of the wood gas (the secondary air inlet blows hot air by the time it travels around the fuel pot).
Host of instructional videos are available on YouTube with further explanation on various websites. A range of construction plans to make TLUD gasifier stoves
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- Andreatta, Dale (January 2007), "A Report on Some Experiments with the Top-Lit Up Draft (TLUD) Stove" (PDF), ETHOS 2007 Conference, retrieved 7 April 2012
- HE Huang-chang; LI Hong-bo (February 2011). "Experimental Study on Tar Characteristics in Top-Lit UpDraft (TLUD) Fixed-bed Gasifier". Journal of Yulin University (Nuclear Power Engineering Design Department, China Nuclear Power Engineering Co.). Retrieved 7 April 2012.
- "Tag Archives: TLUD". Biochar Project Australia. Retrieved 7 April 2012.
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