FREE DETAILED CONSTRUCTION PLANS with clear 3D color renderings

Plans are for a large household size, 110,000Btu/hr, 32kWh, which will heat water for heating needs and generate electricity through a genset fueled from the gasifier.

These plans are offered to you FREE. If you build a gasifier from them,

please consider contributing to my further R&D work. I depend on your generous support!

download 67Mb MPG gasifier/furnace intro video here

John Fedock is building one and documenting details and progress.

Check out his website!

Read about the development of this technology and former prototypes.


This is a completely new design, based on the best of my previous prototypes. Most of my earlier prototype gasifier/combustor systems were based on a rectilinear side-draft gasification flow through a narrow fuel column into a close-coupled combustor surrounded by a ceramic heat exchanger that preheated gasification air, even using fuels with up to 2/3 their weight in water.


I have a design for a gasifier that I want to share with the world. It is the culmination of my 38 years of work in the field, and I think it will solve many of the problems that now plague those modeled after the old WWII Imbert gasifiers. While many recent improvements have been made by dedicated gasifier enthusiasts, it is still an evolving technology, with much scope for new approaches and improvements in the utilization of huge quantities of locally-available waste biomass fuel sources. Biomass- and waste-fueled energy has the potential to contribute much more to global green energy demands. To learn more on this subject, read my Department of Energy report on “Biomass Energy, State of the Technology, Present Obstacles and Future Potential”.

I have finally achieved an optimized gravity flow design that follows more elegant thermodynamics than previous approaches, through a labyrinth of concentric shells and spiral ducts. It thrills me to give the complete set of plans for this new household energy system to you, that you might build and test one and give me feedback in order to improve it, that more local waste products become clean efficient energy.

This latest design, a gasifier/hot water heater I have named Round John Virgin, Roundy for short, honoring the comfort of the winter hearth. Virgin doesn’t apply yet, as it’s still in the womb, so to speak…but just wait ‘till she gets in heat! Roundy is large household size, 110,000Btu/hr, 32kWe, which will heat water for heating needs or generate electricity through a genset fueled from the gasifier.

Actually, since this is a radical take-off from previous prototypes, I don’t know how much energy Roundy will put out in practice……could be substantially more than 32kWe, or less. I expect a very large turn-down ratio, at least 20/1 in combustion mode, with very high efficiencies in condensation mode, perhaps 95% of the High Heat of wet fuels (most furnaces are rated at Low Heat efficiency, since they don’t condense the moisture to get back the heat of vaporization. Since green biomass can often be half water, this represents a significant increase in energy available from condensing the woodgas or exhaust).

Since this unit has not been built yet, I don’t know the performance parameters it will exhibit in actual operation, but I expect it to create a high quality gas, clean enough after the condensing heat exchanger (CHX) for the engine without further cyclone separators or filters. There will be an operating range where the gas is the cleanest, and another condensing range where efficiencies of both gas and hot water production are highest. These parameters will have to be tested to know for sure.

Any fuel that will fit in the hopper and produce a combustible gas can be gasified ~ logs, chips from the tree trimmers, bark, sawdust, corn cobs, leaves, wood-, straw-, municipal solid waste-pellets, green and wet biomass (up to 2/3 water, at least for the water-heating mode), household and farm waste, etc. Ideally, anything that will burn can be vaporized or gasified and turned into a fuel.

A quality fuel gas contains mainly Carbon Monoxide (CO) and Hydrogen (H2), combustible gases, along with the 79% Nitrogen (N2) from the air and the considerable water vapor (H2O) generated by the combustion chemistry as well as held in the fuel. Ideally, the Nitrogen Oxide (NOx) content is very low, and soot, hydrocarbons and other smoke pollutants are non-existent. The steam can mostly condense on grains of fly-ash and the cleansing rain will scrub the gas clean in a properly designed HX. However, the difference between ideal and practical has been significant in the history of gasification, largely because waste fuels are not homogeneous and meterable like gasoline and natural gas. The pieces gasify at different rates, and the difference in moisture, ash, elemental composition, slagging temperature, oxygen and CO2 penetration, feed considerations, etc. present many uncontrolled variables. These challenges have been grist for my explorations into this technology. Round John has been designed from the following


Fuel in a hopper gasifies best and most evenly, without bridging, when it is burned, vaporized, gasified evenly at the base of a vertical-sided hopper. Whenever there is constriction without size-reduction from burning or gasification, as is often the case in the upper throat of an Imbert or constricting throat gasifier, where combustion doesn’t consume the fuel to the contour of the throat, bridging and uneven gasification occurs.