A wood gas generator is a device that heats wood with very little air, so the wood gives off a burnable gas that can run a gasoline engine. It is a proven emergency technology, but it is slow, smoky and dangerous, because the gas is about one-fifth carbon monoxide. For almost every home, a dual-fuel or tri-fuel generator is the better backup.
Maybe you have seen a video of a truck running on firewood. Maybe you want power that does not depend on gas stations. Wood is everywhere, so the idea is very appealing.
This guide gives you the honest picture. You will learn what a wood gas generator really is, how it works, where the famous FEMA design came from, how much wood it burns, why it can kill, and what to buy if you simply want reliable backup power. The technical facts come from the 1989 FEMA and Oak Ridge National Laboratory report on the subject. We have not built or tested a gasifier, and this article is not a set of building plans.
Wood gas generators at a glance
Old technology, real power, serious risks
Figures come from the 1989 report that FEMA published with Oak Ridge National Laboratory. Product details come from current Amazon listings, checked in October 2026.
Quick answer
A wood gas generator, also called a gasifier, turns dry wood chips into a gas that a spark-ignition engine can burn. It does not make electricity by itself. You still need an engine and a generator head. FEMA published a simple design in 1989 for use in a long fuel emergency, and it works. But it needs dry, sized wood, constant attention and skilled metalwork, and its gas is highly poisonous. For home backup power, a propane or dual-fuel generator gives you long-lasting stored fuel without those risks.
How we put this guide together
We have not built, operated or tested a wood gas generator. The facts about how gasifiers work, their history, their fuel use and their hazards come from “Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum Emergency,” written by H. LaFontaine and F. P. Zimmerman and published by FEMA in March 1989. Fuel arithmetic for generators is our own, and we show the working. Product details come from current Amazon listings.
In this guide
- What Is a Wood Gas Generator?
- How Wood Gasification Works
- A Short History: When Millions of Engines Ran on Wood
- The FEMA Emergency Gasifier
- What Wood Gas Is Made Of, and Why Engines Lose Power
- How Much Wood Does It Take?
- Can You Run a Home Generator on Wood Gas?
- The Dangers: Read This Before Anything Else
- Wood Gas Compared With Ordinary Generator Fuels
- Safer Ways to Get Fuel Independence
- Common Mistakes With Wood Gas (and the Fix)
- Pro Tips if You Want to Learn More
- Real-Life Scenarios: Is Wood Gas for You?
- Wood Gas Generators: FAQ
- Your Wood Gas Reality Checklist
What Is a Wood Gas Generator?
The name causes confusion, so let us clear it up first.
A wood gas generator generates *gas*, not electricity. It is a metal vessel that turns solid wood into a fuel gas. That gas is piped to an ordinary engine, which runs on it in place of gasoline.
You will see several names for the same thing.
| Name | What it means |
|---|---|
| Wood gas generator | A unit that makes burnable gas from wood |
| Gasifier | The same thing. The more common modern word |
| Producer gas | The old name for the gas it makes |
| Syngas | A modern name for similar gas mixtures |
| Gazogene | The French name, common in World War II |
| Wood gas stove | A camp stove that burns its own wood gas for cooking. It does not run an engine |
So if your goal is electricity, a gasifier is only one part of the chain. You need a gasifier, a filter and cooler, an engine and a generator head. Our guide on how a generator works explains the last two.
Key insight: a wood gas generator replaces the fuel tank, not the generator. It is a way to feed an engine when liquid fuel cannot be bought.
How Wood Gasification Works
Here is a simple way to see it. Light a wooden match and hold it level. Look closely and you will see a small gap between the wood and the flame. The wood itself is not burning. It is giving off a gas, and the gas burns a little way from the stick. That gas is wood gas.
A gasifier does the same thing on purpose, and it stops the gas from burning so that it can be piped to an engine.
The FEMA report describes a design called the stratified downdraft gasifier. Air is drawn down through four layers.
- The fuel layer. Fresh wood chips sit at the top. Air enters here.
- The pyrolysis layer. Heat breaks the wood down. The gases it gives off burn with the incoming air, and that makes the heat for the whole process. By the bottom of this layer, all the oxygen has been used up.
- The charcoal layer. The hot gases pass through glowing charcoal. This turns carbon dioxide and water vapor into carbon monoxide and hydrogen, which are the fuel.
- The ash layer. Spent char and ash collect above the grate. They protect the grate from the heat.
The gas then goes through a filter and a cooler. Finally it is mixed with air and drawn into the engine. The report says the right mix is about one part air to one part gas.
One detail matters for safety. The engine’s own suction pulls the gas through the system, so the unit runs under slight vacuum while the engine is on. That changes the moment the engine stops, as you will see below.
A Short History: When Millions of Engines Ran on Wood
Wood gas is not a new idea or a fringe one. It kept whole countries moving.
The FEMA report gives the story. Fuel gas was used for heating in Europe as early as 1840, and by 1884 it had been adapted to run engines in England. The big moment came in World War II, when civilians could not get gasoline.
- In occupied Denmark, 95% of all mobile farm machinery, tractors, trucks, stationary engines and fishing and ferry boats ran on wood gas.
- In neutral Sweden, 40% of all motor traffic ran on gas made from wood or charcoal.
- Across Europe, Asia and Australia, millions of gas generators were in use between 1940 and 1946.
Then, almost overnight, they vanished. The report explains why. Most units were abandoned when oil returned in 1945 because of their low efficiency, the inconvenience of running them and the health risks from toxic fumes.
That history tells you two things. Wood gas truly works. And people who depended on it every day gave it up the moment they had a choice.
The FEMA Emergency Gasifier
Most people who search for wood gas generators end up at one document. In March 1989 the Federal Emergency Management Agency published a report written with Oak Ridge National Laboratory.
Its purpose was narrow and clear. It gives instructions for a gasifier that could fuel tractors and trucks if normal petroleum supplies were severely disrupted for a long time. The aim was to keep food production and distribution going in a national emergency.
What makes the FEMA design different
| Point | World War II Imbert gasifier | FEMA stratified downdraft gasifier |
|---|---|---|
| Fuel hopper | Sealed and airtight. Opened to refuel | Open top. No sealed hopper needed |
| Wood needed | Uniform blocks, carefully sized | Any blocky fuel, such as chips |
| Building it | Mass produced in factories | Made from a garbage can, a small drum and plumbing parts |
| Track record | Millions of operating hours | Tested, but without the test of time |
| Best use | Long-term daily service | A simple unit for emergencies |
The report says the body of the unit is a galvanized metal garbage can on top of a small metal drum, with common plumbing fittings and a stainless steel mixing bowl for the grate. A prototype was mounted on a 35-horsepower John Deere farm tractor and ran on wood chips alone.
Who it was written for
The report says it was prepared for any mechanic who is reasonably proficient in metal fabrication or engine repair. That is an honest limit. This is cutting, welding and gas-tight plumbing, connected to a running engine.
The authors are also frank about what it is not. They write that wood gas generators are not technological marvels that can end dependence on oil, but they are a proven emergency solution when fuels cannot be obtained.
What Wood Gas Is Made Of, and Why Engines Lose Power
Wood gas is a weak fuel. The reason is in its recipe.
| Part of the gas | Share by weight | Does it burn? |
|---|---|---|
| Hydrogen | About 20% | Yes |
| Carbon monoxide | About 20% | Yes, and it is poisonous |
| Methane | Small amounts | Yes |
| Nitrogen | 50 to 60% | No. It only takes up space |
More than half of the gas is nitrogen from the air, and nitrogen does not burn. It fills the cylinder without doing any work. So an engine on wood gas makes less power than the same engine on gasoline.
Heat makes it worse. Warm gas is thin gas. The report says the ideal gas temperature at the engine is 70 °F, and that an estimated 1% of horsepower is lost for every 10 degrees above that. This is why a cooler is part of the system.
The report also notes that the engine needs changes to run well, such as a smaller spark plug gap and earlier ignition timing.
How Much Wood Does It Take?
This is the question that decides whether wood gas is practical for you.
The FEMA report gives a simple rule: about 20 pounds of wood has the energy of one gallon of gasoline when used in a gas generator.
The wood has to be right
| Requirement | Figure | Why it matters |
|---|---|---|
| Moisture | Below 20% by weight | Wet wood makes poor gas |
| Green wood | 25 to 60% moisture | Too wet to use |
| Air-dried wood | 12 to 15% moisture | Suitable |
| Kiln-dried wood | About 8% moisture | Suitable |
| Chip size | At least 3/4 by 3/4 by 1/4 inch | Smaller pieces pack and block the flow |
| Block size | Up to 2-inch cubes | Larger pieces bridge and jam |
Sawdust, bark shreds and twigs do not work well. They form a bridge inside the unit and stop the fuel from moving down.
A worked example for home backup
Here is our own rough arithmetic. A 5,000-watt gasoline generator at half load uses about 0.6 to 0.75 gallons an hour.
- Per hour: 0.6 to 0.75 gallons is the same energy as about 12 to 15 pounds of wood.
- Per day: running around the clock, that is roughly 290 to 360 pounds of dry, chipped wood.
- In volume: the report says a cubic yard of wood gives only 500 to 600 pounds of gasifier fuel. So one day could use more than half a cubic yard.
Treat those numbers as a guide only. An engine makes less power on wood gas, so real use may be higher. But the scale is clear. You would be cutting, drying and chipping wood as a full-time job. For normal fuel figures, see how much gas a generator uses.
Can You Run a Home Generator on Wood Gas?
In principle, yes. The FEMA report says stationary engines can be fueled by wood gasifiers to run electric generators, pumps and industrial equipment.
In practice, there are hard obstacles.
| Obstacle | What it means for you |
|---|---|
| Extra equipment | The report says a stationary engine needs a gas cooler and a second filter added to the system |
| Start-up | A blower must draw air through the unit, the fire must be lit, and the gas must be tested before the engine starts |
| Constant attention | The hopper needs refilling and the ash needs shaking down while it runs |
| Dry, sized wood | You need a large stock of chips below 20% moisture |
| Less power | The engine makes less than its gasoline rating |
| Poison gas | The unit holds a gas that is roughly one-fifth carbon monoxide |
| Skilled building | Every joint from the gasifier to the engine must be airtight |
There is one more point. A modern portable generator is sold as a complete, tested machine. Feeding it a home-made fuel is outside anything its maker designed or approved it for.
So our honest view is this. A wood gasifier is a project for a skilled, careful builder who enjoys the engineering. It is not a practical backup for a family that wants the lights on during a storm.
The Dangers: Read This Before Anything Else
The FEMA report puts its safety section at the end, and then warns the reader not to take that as a sign the hazards are minor. We will be just as direct.
Carbon monoxide
Wood gas works *because* it contains carbon monoxide. You cannot filter it out, since it is the fuel.
The report states that many deaths in Europe during World War II were attributed to poisoning from wood gas generators. It says the danger was one of the reasons gasifiers were so readily abandoned when the war ended.
It also describes a trap that is easy to miss. While the engine runs, the system is under suction and leaks pull air in. When the engine is shut off, gas keeps forming for about 20 minutes and pressure builds inside the unit. The report says this shutdown gas contains 23 to 27% carbon monoxide and is very toxic.
Carbon monoxide gives no warning
You cannot see or smell carbon monoxide. The Centers for Disease Control and Prevention lists the symptoms as headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. Any engine or gasifier belongs outdoors, far from doors, windows and vents, and never in a garage or shed attached to a home.
Fire and heat
The report says the outside of the unit can get as hot as a catalytic converter. It calls for clearance around the unit, care near dry grass, and letting the ash cool before it is handled. It also warns that an air leak below the grate lets the gas burn inside the unit, which will almost certainly destroy it.
Wood Gas Compared With Ordinary Generator Fuels
If your real goal is fuel you can store for a long time, look at how the choices compare.
| Fuel | Energy | How it stores | Effort to use |
|---|---|---|---|
| Gasoline | 120,214 Btu per gallon | Goes stale. Needs stabilizer | Pour and start |
| Diesel | 137,381 Btu per gallon | Stores longer than gasoline | Pour and start |
| Propane | 91,452 Btu per gallon | Does not go stale | Connect a cylinder and start |
| Natural gas | 1,036 Btu per cubic foot | Piped in. No storage | Connect and start |
| Wood, in a gasifier | About 20 lb equals one gallon of gasoline | Must be kept dry and chipped | Light, tend, refill and clean |
Propane gives you most of what people want from wood gas. It stores for years in sealed cylinders, and it works in a factory-built generator.
Safer Ways to Get Fuel Independence
Here are four products that fit the goals behind most wood gas searches. Each had an active Amazon listing with an Add to Cart button when we checked in October 2026.
To study the technology
Construction of a Simplified Wood Gas Generator (FEMA report, paperback reprint)
A printed copy of the 1989 report by LaFontaine and Zimmerman. It covers the principles, the stratified downdraft design, operation, troubleshooting and hazards.
- FormatPaperback
- Length66 pages
- AuthorsH. LaFontaine and F. P. Zimmerman
- Original publisherFEMA, March 1989
- Design coveredStratified downdraft gasifier
- Written forMechanics with fabrication skills
- Why it works: it is the primary source that most modern wood gas articles and videos are based on.
- Who it is best for: readers who want to understand gasification properly, and experienced builders who want the original text on the bench.
- What it solves: second-hand advice. You read what the engineers actually wrote, including their warnings.
- Handy to know: the report is a U.S. government document and can also be found free in public archives. The paperback is for people who prefer paper.
- Keep in mind: it describes an emergency design, and its own authors call it the absolute minimum. Reading it does not make building or running a gasifier safe.
As an Amazon Associate we earn from qualifying purchases. Details come from the Amazon listing and the report itself, checked October 2026.
Needed with any engine
Kidde Carbon Monoxide Detector with 10-Year Battery and Digital Display (C3010D)
A battery-powered carbon monoxide alarm that keeps working when the power is out. It needs no wiring.
- Power10-year sealed lithium battery
- SensorElectrochemical
- Alarm85 decibels
- DisplayDigital, updates every 15 seconds
- MemoryPeak level memory
- Warranty10-year limited
- Why it works: it runs on its own battery, so an outage does not switch it off when you need it most.
- Who it is best for: every home that runs a generator, a gasifier or any fuel-burning heater.
- What it solves: the silent danger. The display shows the level, not just an alarm.
- Handy extras: it can hang on a wall or stand on a table, and Peak Level Memory records the last time carbon monoxide was detected.
- Keep in mind: an alarm is a backup. It does not make it safe to run an engine or a gasifier near the house.
As an Amazon Associate we earn from qualifying purchases. Specs come from the Amazon listing, checked October 2026.
Stored fuel that lasts
Champion 4500-Watt Electric Start Dual Fuel Portable Inverter Generator
A factory-built generator that runs on gasoline or propane. Propane cylinders can sit for years and still be good, which is the practical route to fuel independence.
- Gasoline4,500 starting / 3,500 running W
- Propane3,150 running W
- Noise61 dBA
- Run time, gasolineUp to 14 hours
- Run time, propaneUp to 21 hours
- Weight99.2 lb
- Why it works: propane does not go stale, so the fuel you store this year will still start the generator in a later year.
- Who it is best for: households that want a refrigerator, a furnace fan and electronics covered without daily fuel chores.
- What it solves: the stale-gasoline problem that pushes people toward wood gas in the first place.
- Handy extras: electric start, a carbon monoxide shutoff and a 3-year warranty.
- Keep in mind: output drops to 3,150 running watts on propane. Champion quotes inverter run times at a light load.
As an Amazon Associate we earn from qualifying purchases. Specs come from the Amazon listing, checked October 2026.
Three fuels, one machine
Westinghouse 12500 Peak Watt Tri-Fuel Home Backup Portable Generator
A large generator that runs on gasoline, propane or natural gas. With three fuels to choose from, you are rarely stuck.
- Gasoline12,500 peak / 9,500 running W
- Propane11,200 peak / 8,500 running W
- Natural gas9,500 peak / 7,500 running W
- Run timeUp to 12 hours on 6.6 gallons
- Home outletsL14-30R and 14-50R
- Weight215 lb
- Why it works: if one fuel runs short in a disaster, you switch to another.
- Who it is best for: homeowners with a natural gas line or a large propane tank who want whole-home essentials.
- What it solves: fuel shortages, without building anything.
- Handy extras: remote start, low-oil and carbon monoxide shutdown, and a 3-year limited warranty.
- Keep in mind: it weighs 215 pounds, and output falls on propane and again on natural gas.
As an Amazon Associate we earn from qualifying purchases. Specs come from the Amazon listing, checked October 2026.
Want to compare more? Read dual-fuel generators, our tri-fuel generator review and portable propane generators.
Common Mistakes With Wood Gas (and the Fix)
Pro Tips if You Want to Learn More
- Read the original report first. It is short, clear and honest about the risks.
- Learn on paper before metal. Understand the four zones before you cut anything.
- Think about the wood supply. The gasifier is the easy part. A dry, chipped fuel stock is the hard part.
- Treat it as outdoor equipment only. Plan the site as you would for a generator.
- Fit carbon monoxide alarms near sleeping areas, as the CDC advises, whatever fuel you use.
- Check local rules. Open burning and air quality rules differ from place to place.
- Keep your real backup simple. A propane cylinder and a dual-fuel generator ask far less of you in a storm.
Real-Life Scenarios: Is Wood Gas for You?
These are typical situations that people describe in forums and videos. They are examples to help you decide, not quotes from real people.
🔧 The skilled tinkerer
You weld, you rebuild engines, and you want to understand an old technology.
You want a careful outdoor project and the original engineering text.
Best fit: study the FEMA report, then decide
🌲 The rural landowner
You have acres of timber and want power that does not depend on fuel deliveries.
You need stored fuel that lasts for years with little work.
Best fit: a dual-fuel or tri-fuel generator and propane
⛈️ The storm-season family
You want the refrigerator and furnace on when the grid fails.
You need something that starts at once and runs safely.
Best fit: a factory-built generator, not a gasifier
Wood Gas Generators: FAQ
What is a wood gas generator?
It is a device, also called a gasifier, that heats wood with limited air so the wood releases a burnable gas. That gas can fuel a gasoline engine. It makes gas, not electricity.
Can a wood gas generator power a house?
Only as part of a larger system with an engine and a generator head, plus a cooler and filters. It needs constant attention and a large supply of dry wood chips, so it is not a practical home backup for most people.
How much wood equals a gallon of gasoline?
The FEMA report says about 20 pounds of wood has the energy of one gallon of gasoline when used in a gas generator.
Is wood gas dangerous?
Yes. Wood gas is about 20% carbon monoxide by weight, and the FEMA report says many deaths in Europe during World War II were attributed to poisoning from wood gas generators.
What is the FEMA gasifier?
It is a simple stratified downdraft gasifier described in a March 1989 FEMA report. It was designed to fuel tractors and trucks in a long petroleum emergency and can be built from a garbage can, a small drum and plumbing parts.
What is a better alternative to wood gas for backup power?
A dual-fuel or tri-fuel generator. Propane stores for years without going stale and works in a factory-built, tested machine.
Your Wood Gas Reality Checklist
- Decide whether you want a project or reliable backup power.
- Remember that a gasifier makes gas, not electricity.
- Read the original FEMA report before any other source.
- Count the wood: about 20 pounds for each gallon of gasoline.
- Plan how you would dry and chip that much wood.
- Accept that the engine will make less power.
- Treat carbon monoxide as the main danger.
- Keep any engine or gasifier outdoors and away from the house.
- Fit battery-powered carbon monoxide alarms.
- Choose a propane or dual-fuel generator as your real backup.
The bottom line
Wood gas generators are real, and they once kept nations running. They are also slow, hungry and poisonous, which is why people abandoned them the moment gasoline returned. Study the idea if it interests you. For backup power you can trust in a storm, store propane and use a dual-fuel generator.
As an Amazon Associate we earn from qualifying purchases.
Sources: H. LaFontaine and F. P. Zimmerman, “Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum Emergency,” Federal Emergency Management Agency, March 1989; U.S. Energy Information Administration, energy conversion factors; Centers for Disease Control and Prevention, carbon monoxide poisoning basics; current Amazon listings for the book and the Kidde, Champion and Westinghouse products named in this guide. All checked October 2026.
