Efficiency and simplicity have long eluded renewable-fuel researchers, but a Maine scientist has developed a two-step process he says can make oil from the cellulose in wood fiber. This process, far less complex than competing methods, creates an oil that can be refined into gasoline, jet fuel or diesel and removes nearly all oxygen — the enemy of fuel efficiency. “It’s unique and it’s simple,” said Clay Wheeler, the University of Maine chemical engineering professor who discovered the process last year with two undergraduates. “This is important because the more complex the technology, the more expensive it’s going to be.”
In heavily wooded Maine, logging produces a lot of scrap tree stumps, tops and branches that are unusable for making lumber or paper.
While additional research is needed, if Wheeler’s process is ultimately able to be commercially developed, it could help forest-rich states generate their own fuel from that scrap. In the first step of Wheeler’s process, wood is bathed in sulfuric acid, isolating the sugars in cellulose and producing an energy-intense organic acid mixture. That mixture is then heated with calcium hydroxide in a reactor to 450 degrees Celsius (840 Fahrenheit), a step that removes oxygen. What drips out is a hydrocarbon liquid that chemically mimics crude oil.
For every ton of cellulose processed, Wheeler is able to make about 1.25 barrels of oil equivalent, a unit of energy comparable to the amount of energy produced by burning one barrel of crude oil. The acids and calcium hydroxide are recycled at the end of the process, cutting costs, he said. The most expensive part is the wood itself, Wheeler said. At current wood biomass prices, he acknowledged his process is not economically competitive with traditional crude oil refining. “But we anticipate that the value of the fuel will continue to increase as petroleum becomes more scarce,” he said. The economic viability of the project is a source of concern, said Andrew Soare, an analyst who tracks alternative fuel technologies at Lux Research, a technology advisory firm. “Further understanding of costs is key to this reaction,” Soare said. “I think this process certainly does have a chance to go somewhere.” Paul Bryan, program manager at the U.S. Department of Energy’s Biomass Program, said a project’s economics are a key factor for any future funding support.