Wood Gas Wizard

After the energy crisis of the late 1970s, MOTHER EARTH NEWS revisited wood gas as a homegrown fuel option. We had heard from several readers who’d built their own wood gasifiers. Eventually, we had all of these running on wood gas: a Chevy pickup, a sawmill, and a 12.5-kilowatt electric generator for remote power. But why would anyone want to use wood for motor fuel?

1. Abundant Biomass. Wood is biomass that, well, literally grows on trees. In many areas, there are more wood resources than you can shake a stick at. And you don’t need firewood splits to do this — small branches, construction tailings and other wood scraps make the best fuel.

2. Wood Is Carbon-Neutral. Unlike coal or petroleum, which become environmental problems when they are extracted, refined and burned, a tree absorbs carbon dioxide from the air as it grows. When a tree dies, whether it is burned or left to rot, the carbon dioxide is released back into the atmosphere. 

3. Biochar to Enrich Your Garden. When wood is consumed for motor fuel, it creates a byproduct known as biochar. This carbon-rich char can be used as a soil amendment to decrease acidity and reduce nutrient leaching while improving tilth and productivity. (Read more about biochar for gardening in Make Biochar — This Ancient Technique Will Improve Your Soil. — MOTHER EARTH NEWS)

4. Energy Independence. Perhaps the best benefit of wood gas is that wood is a renewable, homegrown fuel. If you have moderate metalworking skills and access to a sawmill, using a wood gasifier can be a major step forward in sustainable, self-reliant living. Wood gasification isn’t for everyone, but it certainly is within reach for many MOTHER EARTH NEWS readers.

Wayne’s Wood Gas World

When I visited Keith on his 100-acre spread, it quickly became clear to me that he enjoys tinkering and has no qualms about getting his hands dirty. Coming up the drive, I spotted the log home he built from his sawmill stock, two homemade wind turbines in the pasture, and several trucks with subtle signs of modifications.

Keith took me to an ’84 Ford truck to show how he had developed his earliest wood gasification designs. Its 460-cubic-inch V8 engine is a behemoth by any measure. Keith says that a large engine is an advantage in a wood gas conversion because wood gas is weaker than gasoline. More specifically, a pound of wood has fewer Btu than a pound of gasoline. (Btu, a standard unit of energy, stands for “British thermal unit,” the amount of heat needed to increase the temperature of 1 pound of water 1 degree Fahrenheit.) The Ford came with a carburetor; Keith says modern trucks with multi-port fuel-injected engines convert better to wood gas. 

As we got in the wood gasification truck, I expected him to ignite the wood in the gasifier — the main tank that holds the wood chunks and converts them to gas — but he turned the key and away we went. I assumed he was starting on gasoline to warm up and we’d light the tank soon. But a few moments later, he moved a lever beneath the dash, and without any hesitation from the truck, we were driving on 100 percent wood gas.

I was surprised. First, I had no idea the wood gasifier was even lit. From my past experiences with wood gas, I expected a faint smell of burnt wood lingering around the vehicle. Not here. Second, I’d never felt such a smooth transition from gasoline to wood gas, even with a well-stoked fire in the burner. When Keith told me he hauls 15,000 pounds of large, round hay bales with this truck, I was floored. If an “alternative” fuel can pull a 7-plus ton load, why do we even need petroleum?

As we cruised along the county roads, Keith talked about his motivations for powering the majority of his transportation and farm operation with wood gas. 

“From what I’ve read, we are spending $2 billion a day to go after petroleum,” he says. “At that rate, some of these other countries are going to own us. But I’ve got plenty of biomass from my sawmill. As far as I’m concerned, the buck stops here.”

Keith started reading about wood gas during the late 1970s. Decades later, he turned to hands-on trial and error, which proved to be his path to success. These days, Keith almost exclusively uses scrap wood to fuel his trucks.

Keith’s “wood chunker” (fabricated from the differential and a brake drum of an old International truck; see it in action in the Wayne Keith Wood Chunker video), cuts on an ascending bevel so that every revolution of the drum slices off a roughly 2-inch chunk. Keith and his wife, Lisa, lay out the chunks on tarps so they will dry in the sun. After the chunks are dry, Keith stores them in old feed sacks, several of which are easy to keep in a truck bed. The chunker is powered by a thrifty two-cylinder diesel engine. One hour of work can cut and spread up to 2,000 pounds of wood chunks suitable for driving (after drying).  

Tests conducted on Keith’s 1993 Dodge Dakota by David Bransby — a professor of energy crops in the Department of Agronomy at Auburn University and Keith’s partner on a coast-to-coast wood gas tour — showed that it takes 16 pounds of dried wood to take the wood gasification truck as far as 1 gallon of gasoline would (21 miles in conservative driving). So one hour of work with Wayne’s chunker produces the equivalent energy value of 125 gallons of gasoline (a value of $437.50 if gasoline costs $3.50 a gallon) that Wayne can use to travel 2,625 miles. 

What about environmental costs? I asked Keith whether anyone has challenged the impact of his vehicles.

“I have never cut a live tree to heat my house or run the trucks … fact is, the gasifiers prefer small limbs and rough chunks from the sawmill,” he says. “And using that in my trucks does not change the natural, carbon-neutral cycle of wood.”

As for tailpipe emissions, one informal test found that the Dakota would meet California’s emissions standards — traditionally the toughest in the nation. More specifically, Bransby contrasts the energy source for Keith’s truck with the main sources of utility energy in their area. 

“Wayne’s truck is 67 percent cleaner than an electric vehicle charged on the Alabama grid, because 67 percent of the electricity in Alabama comes from fossil fuels,” Bransby says. “Specifically, 59 percent coal and 8 percent natural gas.”

Wood Gasification 101

Just like gasoline or diesel, wood is a carbon-based fuel. But because wood is solid, it must be converted into a gas before it can power an engine, much like gasoline or diesel must be atomized before they can be ignited. Traditional burning isn’t sufficient — the wood must be heated in a high-temperature, oxygen-starved environment in order to chemically convert and produce the ideal mix of combustible gases in a process called pyrolysis.

When that conversion happens, wood gas is more effective than gasoline. Wood has less Btu “punch” than gasoline to start with, but gasoline loses some of its Btu punch in the conversion to a mist. In Bransby’s 2010 tests, the Dakota achieved 21 mpg on gasoline and 29 “mpg” on wood gas.

Like any typical wood gasification system, Keith’s setup has three basic components: a gasifier, a radiator and a filter.

The wood gasifier consists of upper and lower chambers in the form of drums connected in the middle by a heavy spacer. The upper drum is a lidded hopper where the wood chunks are held. There is an internal air inlet manifold that introduces oxygen a few inches from a restriction, which causes a high temperature (about 2,700 degrees) to be created in a small environment. This is where the gasification takes place.

The hot gases go from the gasifier to a heat exchanger, where the gaseous fuel is cooled with fresh air. The incoming air piped to the gasifier’s inlet never comes in contact with the exiting fuel gases.  

Next, the gases go to a radiator, or cooler, which Keith has skillfully camouflaged as a bed rack. There are two inlets and two outlets, so each side of the rack has cooling capacity. Here, the gas temperatures drop below the dew point, and the condensation drains into small tanks.

The third component, the filter, is simply a clamped-lid barrel filled with hay. This removes most of the particulate matter contamination in the wood gas.  

After being cooled and filtered, the wood gas is pulled through two branches of PVC piping to the engine compartment. Homemade “slingshot” filters separate any remaining moisture and particulate matter from the incoming gas stream.

The cooled, clean wood gas is directed to fittings Keith has installed in the engine’s air cleaner housing. Two inlets are dedicated to fuel gas and two to fresh air, which is drawn in through separate canister filters. Each of the four inlets includes a butterfly valve that Keith adjusts manually with controls on the dash.

The World’s Fastest Wood Gasification Truck

Impressive as the old Ford was, I was eager to see Keith’s seventh wood gas truck conversion, the ’93 Dakota. Just days before I arrived, Wayne and his son Tally had returned from the Bonneville Salt Flats in Utah, where MOTHER EARTH NEWS sponsored Keith in the famous World of Speed time trials. Not only was Keith’s Dodge Dakota the only wood-powered vehicle there, he was the only competitor to actually drive (not trailer) the vehicle to the event — a distance of about 2,000 miles. (See photos of the Dakota and more in this article’s Image Gallery.)

“We made 73.09 mph in the measured mile,” Keith says. “I beat out 12 other vehicles that were running [in other categories] on gasoline, and beat the team with the prior wood gas record of 47.7 mph.”

(Read 73 MPH On Wood Gas Sets New Record to learn more. But 73 mph isn’t the Dakota’s top speed. MOTHER EARTH NEWS Managing Editor John Rockhold took a ride that had to slow down at 84 mph; read about it and watch it happen in I Went 84 MPH in a Wood Gas Truck; see the third video from the top. — MOTHER EARTH NEWS)

In preparation to start the Dakota, Keith flipped the switches on a pair of small in-line bilge blowers and opened the gasifier lid to reveal remnants of cold char in the tank, which he ignited with a propane torch.

“With a poker rod I make a little void that goes down to the center of the hearth,” Keith says. “I’ve got those blower switches fixed to where I can either blow or suck the air through to get the wood going.”

After pouring a sack (about 12.5 pounds) of dried wood chunks into the chamber, he sealed the lid and started the truck on gasoline. We drove about a quarter of a mile on gasoline, then he switched over to wood gas with the touch of a lever.

“On this truck, I’ve got a sensor and gauge that monitor the exhaust gas, telling me if it’s too rich, too lean or just right,” Keith says. “I’ve also got vacuum and temperature gauges — sort of like a doctor’s stethoscope and blood pressure monitor — that let me keep an eye on what’s going on. Since wood gas is slow-burning, it helps to advance the timing a bit. The older Ford does that with a cable, but the newer models are smart enough to automatically adjust to the fuel.”

On a straight stretch of road, we cruised at 75 mph. Other than monitoring the gauges, Keith did not spend much time making adjustments. Aside from the occasional flick of extra levers and the barrels in the truck bed, you wouldn’t know this truck runs on wood instead of gasoline.

As far as how the wood gas system performs throughout the year, Keith says the vehicle performs slightly better on crisp days, when humidity is lower. 

“The gasifier works fine in hot weather,” he says. “It increases in power a bit the colder it gets. In very cold weather there could be issues with the condensation freezing, so you’d have to design for that.”

As far as driving range, Keith sized the Dakota’s wood gasifier to allow 50 to 75 miles on one fill. Some of his earlier gasifiers were sized to allow 100 miles or more, but that required more conspicuous tanks.

Wood Gas Revolution?

Clearly there is untapped potential in wood gasification for transportation, but whether it can ever be more than a fringe movement remains to be seen. Making it work isn’t easy. Even Wayne Keith — arguably the best advocate for wood gas — says that 75 percent of success comes down to operator knowledge and experience; the system itself accounts for the remaining 25 percent.  

Despite all the money that Keith has saved via wood gas, it’s the self-reliance that is the most satisfying benefit.

“The big plus for me — beyond the clean driving and financial benefits — is being dependent on no one but myself for fuel.”

Wayne Keith’s Wood Gasification Conversion Tips

• Choose a truck with ample room under the hood, as well as around the engine and chassis.
• Electronic fuel-injected engines have streamlined air intakes, which convert better than carbureted engines.
• Multi-port fuel injection is preferable over throttle-body injection. Generally, trucks built after the mid-1980s use fuel injection.
• Large-displacement engines have more power and give better results on wood gas.
• High compression improves performance with wood gas: It burns slowly and has great antiknock qualities. Wood gas supports a compression ratio of up to 16:1.
• It is possible to convert diesel engines to use wood gas, if given the correct compression ratio. But the injector pump has to furnish the ignition with at least 5 percent diesel.
• Ignition timing should be advanced because of the slower-burning gas. Modern engines with electronic ignition will automatically advance the timing.
• It takes about 200 to 300 hours to convert a truck to wood gas. Keith’s record-setting Dodge Dakota took 250 hours of work.
• The cost of materials to convert is about $500. Many components can be found free.
• Tools needed: basic mechanic’s tools, a sheet metal nibbler, a metal-cutting reciprocal saw, a power hacksaw, a drill press, a cutting torch, small wire-feed welder, a solid workbench, and a sturdy vise.  
• The gasifier should be built to match the size of the engine and its airflow volume.
• The size of the wood chunks affects engine performance. Smaller chunks react faster and give better performance, but the fuel is consumed faster.
• Hardwood has greater energy density, and thus delivers more range per fill, than softwood.
• Ongoing maintenance: flushing the cooler and draining the condensation traps every 2,000 miles. Ash residue should be removed every 1,200 miles and the filter medium changed once a year. 
• Moisture content of the wood chunks should be less than 25 percent.

Wayne Keith’s Wood Gas Wonders

• About 250,000 miles driven, almost exclusively on wood gas, since 2004.
• About $40,000 saved by not buying gasoline.
• Nine trucks converted to wood gas since 2004.
• Regularly hauls loads of 15,000 pounds in farm work.
• Completed the 2009 Bio-Truck Coast-to-Coast and Back tour, which ran from Alabama to Charleston, S.C., to Berkeley, Calif., and back to Alabama.
• Completed the 2009 Escape from Berkeley road rally, which ran from Berkeley, Calif., to Las Vegas. Finished second to Jack McCornack’s MAX car (visit 100-mpg Car: MAX to learn more), partly because of a flat tire on the wood chip trailer.
• Set new speed record for wood gas (73 mph) in the 2011 World of Speed event at Utah’s Salt Flats. Read 73 MPH On Wood Gas Sets New Record to learn more.  

Wood Gas Resources

MOTHER EARTH NEWS Wood Gas Adventures blog
Learn more about gasification and see videos of various vehicles in action, including Wayne Keith’s.

Drive On Wood!
Wayne Keith’s website. Keith is working on a book with detailed plans for his system.

Yahoo! Groups: Wood Gas
The Wood Gas community group on Yahoo! has numerous wood gas veterans among its members, including moderator Mike LaRosa.

Richard Freudenberger was a Senior Editor at MOTHER EARTH NEWS from 1978 to 1990. He currently is the publisher for BackHome magazine, and his most recent book is Alcohol Fuel: A Guide to Making and Using Ethanol as a Renewable Fuel.