This page will address components of the gasifier. A fema woodgas generator has only two moving parts, the shaker grate and the shaker handle, all other parts are stationary. Each part of the fema gasifier will be discussed as well as changes to the fema plans on the showcased build.

  • Gasifier body

This includes the burn tube, shaker grate, shaker handle, clean out, top plate, and ignition port.

  • Filters

Filters in this system include a cyclone filter as well as a sawdust filter.

  • Plumbing

This is the path the gas takes from component to component.

  • Fan

This is what creates the downdraft through the biomass gasifier on start and warm up.


Gasifier body

The main body can be constructed from any assortment of containers, it can be round oval, square,… shape is unimportant. For this build i used a sixteen gallon grease drum. The top of the gasifier is a doughnut cut from 1/8″ plate with a center hole cut for the burn tube O.D. The burn tube length and diameter is determined by the H.P. of the engine you desire to run on your gasifier generator, all of the dimensions can be found in the fema plans under the plans link on the menu. The shaker grate in this build was constructed from an eight inch stainless bowl that was then drilled with three hundred and one 1/8″ holes basically turning the bowl into a collander, this bowl is suspended from chains and hangs below the burn tube. An important thing to note is the fuel size you can use is directly related to the hole diameter you drill in your bowl, larger blockier fuel would require larger holes 1/2″ or so. The bowl is then connected to a handle that protrudes from your gasifier body. This gasifier has two ignition ports one according to the fema plans and another of my own design. My ignition port extends through the body and is welded to the burn tube which has a matching hole drilled into its side. This creates a direct path to your fuel and provides an instant one match start up. See the “start up” page for a great demo of this port in action. Your gasifier will need a clean out port or a place to remove bio char and ashes from running the gasifier. I clean out the gasifier after about one hundred and fifty pounds of material has been consumed. The clean out can be any air tight method you prefer. I built a flange style, the larger your clean out is the easier it will be to remove ash. An exellent video describing in much greater detail can be found on the videos page ” How i built my gasifier #1 ” it covers all aspects of building the gasifier generator body construction


In this system there are two filters, the first is a cyclone filter and the second is a sawdust filter. The cyclone filter is the first filter in the system, it’s job is to remove large particles from the gas, this it accomplished by spinning the gas at a high rate of speed, centrifical force removes heavier particles that drop out from the gas flow and are collected in a jar mounted to the bottom. The second filter in the system is the sawdust filter and is another design of my own. The sawdust filter body is made from a six gallon salvage drum, a 2″ pipe is welded about 1″ above the bottom of the drum and extends almost all the way through the drum, the 2″ pipe has a cap welded to the end of it inside the drum and in the bottom 1/3 radius of the pipe one hundred and fifty 1/4″ holes were drilled, this lets the gas escape out the bottom of the pipe and filter up through the sawdust, The sawdust i fill this filter with is douglas fir straight from a chainsaw. The filter drum is filled almost to the top of the drum aproximately two to three inches from the top rim. That’s it for the sawdust filter drum, a very simple build but an incredibly important part in the system. Videos ” how i built my gasifier #2 and #4″ explain both styles of filter.


The piping system that carries your gas to and from each component in the system serves two purposes, it provides a path for the gas and it also helps cool the gas which is why for this build i left the entire piping system raw steel. In this system 2″ automotive exhaust pipe was used. I chose automotive exhaust pipe for several reasons. Exhaust pipe is readily available at thousands of auto parts stores. You can purchase pre bent pieces, adapters, flanges etc. and generally exhaust pipe is reasonably priced. Another reason i chose this style of pipe was because of its thickness, exhaust pipe is fairly thin and as a result dissipates heat and cools your gas much more effeciently than a thicker material would. Auto exhaust also lasts a long time and longevity is always on my mind with any project i undertake. One thing to consider is make sure whatever pipe you use has a larger I.D. than the intake port of the engine you wish to power. I personally would not build a piping system smaller than 2″. Check out “how i built my gasifier #3″ on the videos page for more.


The fan is an important part of a wood gasifier, it keeps the downdraft going while starting, warming up and flaring off gas. The fan on this gasifier was made from a mix of old parts that were salvaged from various sources. When fabricating a gasifier keeping everything air tight is top priority and the fan is no different. You can use A.C. or D.C. For this build i used D.C. I like the ease and flexibility of D.C. Fan speed is also important, too slow and the fan will not be able to pull gas through the system. Too fast will result in excess heat and make flaring gas difficult. I highly recomend installing a speed control on your fan for both A.C or D.C to adjust fan speed to your gasifiers liking. “How i built my gasifier #5″ on the videos page has more details.