ALL Power Labs: Tools for Power Hacking
gek assembled downdraft reactor rings reactor inside


The Basics

The Science of Gasification

Gasifier Types

How to Build a Gasifier
Gasifier Experimenters Kit (GEK)
Quadrafier (4 in 1)
GMC truck
Other Designs Online

Gasifier System Components

Technical Resources
Gasification Worshop (June, 08)

back to Gasfier Experimenters Kit

Resources for Gasification

Downdraft Gasifier Types


Downdraft Gasifier Sizing

Here's some rough equivalencies, approximations and rules of thumb to understand downdraft gasifier gas flow needs, HP equivalencies and reactor sizing. For engine applicatons, I find it easier to size by actual HP needed, not by swept volume x RPM. Seldom is an engine running at wide open throttle, as such calculations suggest.

In general, size your gasifier for typical power needs, not the rare max rates. If in doubt, err on the size of too small to lessen tar risks from too low of temps.

Here's how to approximate the relationships of liquid fuel to HP to KWe in your vehicle or genset:

1 gal of gasoline or diesel produces about 15HP mechanical for one hour, or 10kwh electricity in a genset.

How much HP is your vehicle using at cruise?
60MPG = 1gal/hr or 15HP for one hour
30MPG = 2gal/hr or 30HP for one hour
15MPG = 4gal/hr or 60HP for one hour

Solid biomass to syngas to power:

The best figures on Syngas - HP - KW equivalencies are found in the Fluidyne engine tables at Here's some important excerpts, with minor additions by me. Thank you goes to Doug Williams for authoring these numbers.

(Note: If confused, ignore these details and skip to the rule of thumb at the end of the section)

1kg of wood 15% moisture content produces 2.185 cubic metres of gas
or 3.165kW heat from burning gas direct
or 0.837kW of shaft power (i.e engine)
or 1.12HP of shaft power (i.e. engine)
or 0.754kW of electric power generated

1lb of wood at 15% moisture content produces 35 cubic feet of gas
or 4,900 BTU heat from burning the gas direct
or 0.51 HP of shaft power (i.e engine)
or 0.342kW of electric power generated

1HP = 1.95 cubic meters of gas per hour
5HP = 9.75 m3/h
10HP = 19.5 m3/h
50HP = 90.75 m3/h
100HP = 195 m3/h

Thus, the main rule of thumb to remember:
2 lbs biomass ~ 1 kg of biomass ~ 2 m3/h of gas ~ 1HP

Nozzle and Constriction (Imbert) type sizing charts

Once you convert your HP needs to gas flow rates, use the following charts to determine starting dimensions for your reactor (hearth, restriction, reduction bell, nozzles, etc).

Stratified Downdraft type sizing chart

Fuel Combustion Characteristics

Books of Interest

Handbook of Biomass Downdraft Gasification
Thomas Reed and Agua Das, SERI/SP-271-3022, DE88001135, March 1988.
(available in print from BEF at please support BEF. the entire BEF library is fabulous. buy the whole thing.)

FAO 72: Wood Gas as Engine Fuel
ISBN92-5-02436-7, UN Food and Agricultural Organization, 1986

FEMA Manual- Constructing a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum Emergency
Henry LaFontaine, F.P. Zimmerman, March 1989
(available in print from please support BEF. the entire BEF library is fabulous. buy the whole thing)

Biomass Gasifier "Tars": Their Nature, Formation and Conversion
T.A. Milne, R.J. Evans, N. Abatzoglou, NREL, November 1998
(available in print from please support BEF. the entire BEF library is fabulous. buy the whole thing)

Papers of Interest

Superficial Velocity- The Key to Downdraft Gasification
T. B. Reed, R. Walt, S. Ellis, A. Das, S. Deutch. Presented at 4th Biomass Conference of the Americas; Oakland, CA, 8/29/99
(mirrored from Biomass Energy Foundation,

Monorator- Gasifier for D
amp Fuel
Harald Kyrklund, Teknisk Tidskrift, July 21 1945.
(Translation 2000, Joacim Persson <>)
(mirrored from:

Lutz: German Ideas on Improvements of Wood Gasifiers
Summary in Teknisk Tidskrift of a thesis by H. Lutz, published in ATZ. Ed CVNordenswan, Sept. 1941.
(Translation to English, 2000, Joacim Persson <>).
(mirrored from:

Comments on Lutz paper: Gasifier Efficiency
E. Hubendick, Teknisk Tidskrift, Dec, 1941
(Translation to English, 2000, Joacim Persson <>)
(mirrored from:

The Making of the Kalle Gasifier
Torsten Kalle, January-February 1942.
(Translation to English, 2000, Joacim Persson <>)
(mirrored from:

Modelling for Control of a Biomass Gasifier
Dorus van der Hoeven, Thesis 0474218, Technische Universiteit Eindhoven, January 2005


Questions? Contact: gek_at_allpowerlabs_dot_org

downdraft reactor rings