[Gasification] W-Gas and P-Gas defined

Thomas Reed tombreed2010 at gmail.com
Sat Dec 10 07:34:17 CST 2011

Dear Gasification list

Well defined terminology is fundamental to a discussion of the science and praxis of any subject.   I am proposing two new words for the different gases we make.  They will help clarify  discussions we have and will have here at the "Discussion of biomass pyrolysis and gasification " list.  

These are proposals, and I hope they will spark a discussion of this and other terms that have grown up helter skelter.  We welcome alternate suggestions.  


WOODGAS is a term I have been using for thirty years.  In German it is Holzgaz, an exact translation, holz being the German name for wood.  It refers to the gas made in gasifiers that completely convert wood to combustible gas, often for use in IC engines.  It is the name of our website where we sell books on gasification and Woodgas cookstoves.

For this discussion and others, I propose the abbreviation "W-Gas".

Wood is composed of ~20% lignin and ~80% cellulose (cellulose plus hemicellulose). On heating in the absence of air, the cellulose produces mostly the Woodgas, while the lignin is converted to charcoal.  Since the lignin is the principal source of tars in Woodgas (up to 2% by weight of the wood) tar removal is a very big problem for using W-gas in engInes.  


More recently (starting in 1985)  we have developed a new form of "PYROLYTIC gasification" in which air is admitted to a dense bed of wood pellets, chips or sticks, forming an auto pyrolysis zone passing up or down through the bed and burning a small fraction of the pyrolysis gas to convert the remaining cellulose to a combustible gas which can be used for cookstoves and charcoal generation. Paul Anderson has dubbed the stoves "TLUD, Toplit Updraft" stoves.  

The TLUD gas composition has not been well characterized yet, but I'm hoping someone will do so soon (possibly me). ( In an attempt to measure tar, I condensed about 1/2 % of a non sticky grey soot in a four foot X 4" galvanized stove pipe.). 

I propose the name "P-Gas" for the gas made from mostly the cellulose in this process.

(Incidentally, the charcoal made in this 600-800C process is significantly different from conventional charcoal, and has much less tar and much higher absorption properties.  It could be called PG- (PYROLYTIC gasification) charcoal. )


I hope that this will spark a discussion of this and other terminology used in this list.  Since Tom Miles is the moderator of this list, I'd like to appoint him as the final arbiter of terminology for the list.

Dr Thomas B Reed 
The Biomass Energy Foundation

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