This school press release says the bio-oil replacement for non-renewable petroleum is added to the mixture known as Bioasphalt:
If the demonstration and other tests go well, “This would be great stuff for the state of Iowa,” said [Iowa State University’s Christopher Williams], an associate professor of civil, construction and environmental engineering.
He said that’s for a lot of reasons: Asphalt mixtures derived from plants and trees could replace petroleum-based mixes. That 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.
Bio-oil is created by a thermochemical process called fast pyrolysis. Corn stalks, 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.
Officials hope that if this test of 5 percent Bioasphalt is successful, they’ll be able to use higher blends later.