Update: Oils derived from wood chips could reduce cost of biofuel

Posted by Wolfgang Gruener

Athens (GA) - The search for renewable energy sources is gaining traction and researchers from the University of Georgia now say they have found a way to use wood chips for the generation of biofuel that can be blended with biodiesel and petroleum diesel to power conventional engines.
 
The idea to extract oils from wood isn’t an entirely new idea. What makes the approach of the University of Georgia research team interesting, however, is that they have developed a simple method of extracting oils that by itself may not be suited to power engines, but it may help to reduce the price of producing fuels from biomass. The scientists claim that the yet to be named fuel can complement biodiesel and even petroleum-based diesel to run traditional engines.

To create the wood-fuel, the research team uses a process known as pyrolysis, in which wood chips and pellets are heated in the absence of oxygen at a high temperature. About one third of the dry weight of the wood turns into charcoal, the rest turns into gas. Most of this gas can be condensed into a liquid bio-oil and chemically treated. Currently, about 34% of the bio-oil created in this process can be used to power engines, the scientists estimated and added that they are working on improving the process to “derive even more oil from the wood.”  

 

 

The downside, at least for now, appears to be that the approach appears to be requiring a lot of wood. The researchers estimate that about 15-17% of the dry weight of the wood can be converted into biofuel, translating into about 41 pounds of wood to generate 1 gallon of biofuel with a weight of roughly 7 pounds per gallon. Even as an add-on to regular bio-diesel or petroleum diesel, this approach would  require a lot of trees to be cut down to power, for example, car engines on a mass market basis.

However, the University of Georgia researchers say that the approach has its advantages, including cheap production cost and environmental benefits. According to said Tom Adams, director of the UGA Faculty of Engineering outreach service, the fuel is nearly carbon neutral, meaning that it does not significantly increase heat-trapping carbon dioxide in the atmosphere as long as new trees are planted to replace the ones used to create the fuel.

Replanting and re-growing those trees in fact may be the major challenge for this technology. While “Georgia has 24 million acres of forested land,” according to Adams, and the state could use the technology to increase employment and tax revenues and somewhat decrease the amount of fuel the U.S. needs to import from other countries, tress have a tendency to grow not that fast. According to the Ohio Department of Natural Resources, relatively fast growing trees such as pine trees, need about 50 to 60 years to reach a mature height between 100 and 120 ft. and about 25 years to reach a harvestable height of 40 ft. Sycamore trees, which are typically used for oil extraction projects, are also estimated to need about 20 to 25 years to reach a height of 40 ft.

 

Update

Tom Adams from the University of Georgia followed up with us and our concerns that generating biofuel from wood may result in cutting done many trees. In fact, he shared our concern saying that growing pine trees in a farm currently provide only about 2 tons of wood per acre per year.

However, he suggested that he suggested that other plants that can be harvested once a year, such as grasses, may provide more bio-mass and may end up more suited to become a source for bio-fuels. For example, he said that switchgrass grows about 6 tons of biomass per year. Also, Adams believes that currently unused bio-mass when trees are harvested could be used for his method of producing bio-fuel – he estimates that about 15% of bio-mass is wasted when trees are cut down these days.

So, how much bio-fuel could be generated in this way and how much would it cost? According to Adams, there is enough low-quality bio-mass (as opposed to high-quality biomass that is also used for food products) in the U.S. to cover about 30% of the fuel needs of Americans. It is not enough to completely make the country independent from fuel imports today, but combined with petroleum available in the U.S. and a more conscious use of energy it could minimize oil imports to the U.S., Adams believes.

In terms of cost, the scientist estimates that low-quality biomass-based crude oil that has the same density as today’s bio-diesel could be produced for about 50 cents per gallon. However that excludes the process to refine the bio-fuel for a mass market use. Add this cost as well as a profit margin and you could be imagining bio-diesel that is available to Americans for less than $1.50 per gallon.