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Bioasphalt Could Create New Market for Iowa Crop Residues

Bioasphalt Could Create New Market for Iowa Crop Residues

Bioasphalt developed at Iowa State University is being used and tested on a Des Moines bike trail. It's another step toward moving away from reliance on petroleum.

Iowa State University's Christopher Williams was just trying to see if adding bio-oil to asphalt would improve the hot- and cold-weather performance of pavements. What he found was a possible green replacement for asphalt derived from petroleum.

That finding will move from Williams' laboratory at the Institute for Transportation's Asphalt Materials and Pavements Program at ISU to a demonstration project this fall. The project will pave part of a Des Moines bicycle trail with an asphalt mixture containing what is now known as Bioasphalt. If the demonstration and other tests go well, "This would be great stuff for the state of Iowa," says Williams, an associate professor of civil, construction and environmental engineering.

He says that for a lot of reasons: Asphalt mixtures derived from plants and trees could replace petroleum-based mixes. This use could create a new market for Iowa crop residues. It could be a business opportunity for Iowans. And it saves energy and money because Bioasphalt can be mixed and paved at lower temperatures than conventional asphalt. It is being tested to see if it can meet the demands of truck traffic and weather.

Bio-oil is created by heating-chemical process called fast pyrolysis

Bio-oil is created by a thermochemical process called fast pyrolysis. Cornstalks, wood wastes or other types of biomass are quickly heated without oxygen. The process produces a liquid bio-oil that can be used to manufacture fuels, chemicals and asphalt plus a solid product called biochar that can be used to enrich soils and remove greenhouses gases from the atmosphere.

Robert C. Brown – an Anson Marston Distinguished Professor of Engineering, the Gary and Donna Hoover Chair in Mechanical Engineering and the Iowa Farm Bureau director of Iowa State's Bioeconomy Institute – has led research and development of fast pyrolysis technologies at ISU. Three of his former graduate students – Jared Brown, Cody Ellens and Anthony Pollard, all December 2009 graduates – have established a startup company, Avello Bioenergy Inc. That firm specializes in pyrolysis technology that improves, collects and separates bio-oil into various liquid fractions.

Another step toward moving away from reliance on petroleum

Williams used bio-oil fractions provided by Brown's fast pyrolysis facility at ISU's BioCentury Research Farm to study and develop Bioasphalt. The research was supported by the Iowa Energy Center and the Iowa Department of Transportation. Avello has licensed the Bioasphalt technology from the ISU Research Foundation Inc. and has produced oak-based bio-oil fractions for the bike trail project using funding from the Iowa Department of Economic Development. Williams says the project will include a mix of 5% Bioasphalt.

The mixture contains no more than 5% bioasphalt, which is not a huge change from regular asphalt. But it's a step in the right direction, says Brown. This product can use any kind of biomass, from wood chips to corn stover such as cobs and leaves, and also miscanthus, a grass that is touted as the best alternative to corn as a feedstock to product bio-oil.

Tests will see if it can meet demands of truck traffic and weather

Jeb Brewer, city engineer for the city of Des Moines, says the Bioasphalt will be part of phase two of the Waveland Trail on the city's northwest side. The 10-foot-wide trail will run along the west side of Glendale Cemetery from University Avenue to Franklin Avenue. "You can do all the tests you want in the lab, but eventually you have to take it outside," he says.

Brewer says the demonstration project is a good fit for the city. "We have a fairly active program for finding ways to conserve energy and be more sustainable," he adds. "We're interested in seeing how this works out and whether it can be part of our toolbox to create more sustainable projects."

Contractors involved in the Bioasphalt demonstration project are Elder Corp. of Des Moines, Bituminous Materials and Supplies of Des Moines and Grimes Asphalt and Paving Corp. of Grimes with the Asphalt Paving Association of Iowa supporting the project. Avello and Bioasphalt are registered trademarks of Avello Bioenergy, Inc. ISU's Williams says a successful demonstration would lead to more pavement tests containing higher and higher percentages of Bioasphalt. "This demonstration project is a great opportunity," he notes. "We're introducing a green technology into a green environment in Des Moines. And it's a technology that's been developed here in Iowa."

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