Wayne Keith has converted his pickup to run on scraps of wood from his Alabama (US) sawmill. The heart of the wood-powered vehicle is a gasifier, which basically converts solid fuels into gaseous ones. Though the fuel in their tanks is liquid, gasoline and diesel engines actually run on vapour. Thus, the wood gas produced in a gasifier (also known as ‘producer gas’ or ‘syngas’) will burn in a gasoline or diesel engine with only minor modifications to the motor itself.
When heated in the absence of oxygen, wood gives off a mixture of gases made up of about 20% hydrogen, 20% carbon monoxide, and small amounts of methane, with nitrogen accounting for the rest. The gasifier keeps the gas from combining with oxygen until it reaches the engine, where it combusts, giving off carbon dioxide and water vapour as waste products.
This technology is not new. Wood gas has been produced for heating since at least the late 1700s, and has been used to run engines since the 1880s. During WWII’s petroleum shortages, wood gasification for transportation fuel became rapidly and briefly widespread, both in the Europe and the US.
Keith’s converted pickup starts on gasoline. As a supercharger pulls air through the gasifier, he tosses a piece of burning newspaper into the bottom of the unit. The burning paper ignites the charcoal, and 45 seconds later, the engine is running on wood gas alone (though it takes longer to get to full power).
With two separate accelerators, Keith says, the pickup can switch from gasoline to wood fuel “in the blink of an eye.” The gasifier looks like a large drum standing upright in the bed of the pickup. Keith has added five layers of insulating material around the outside of the unit, so that even with temperatures reaching 2,500°F inside, he can stack bales of hay next to it without risking a fire.
Thus equipped, the pickup easily reaches cruising speeds of 100 km/h. A similarly modified truck pulls a trailer loaded with 17 round hay bales, weighing 500 kg apiece. “I’ve driven 30,000 miles (over 48,000 km) in the last three years,” Keith says. “I’ve done 90% of that on wood.” At 2 miles per lb (7 km per kg) burned, it takes 20 lb of wood to replace a gallon of gasoline. That works out to around 4,000 miles per cord of wood, says Keith, whose entire fuel supply comes from his sawmill’s leftovers.
“I’ve never cut a tree to run my truck or heat my house,” he says. Keith says he has no plans to develop his homemade gasifier unit for commercial production, since operating it requires more skill than a standard gasoline or diesel engine. “is whole system is kind of complicated to build and drive,” he explains. “The knowledge is a lot more important than the apparatus itself. It’s kind of like if somebody gave you an operating table and a knife and asked you to do heart surgery.”
A better use for the technology, he says, would be stationary wood gasifiers for generating electricity. Located throughout a county and staffed with trained operators, he says, such small units could be tied into the electrical grid to provide power from scrap wood, spoiled hay, and other unused biomass.
