Some call bio-oil the poor relation of biofuels. There is no established market for it, and, until recently, there has been little advocacy on its behalf.
That may be about to change. Major oil companies like ConocoPhillips are now working to develop bio-oil from cellulosic materials such as corn stalks, stems, leaves and other non-food agricultural residues, as well as hardy grasses. ConocoPhillips recently entered into a research partnership with Iowa State University and the National Renewable Energy Lab to evaluate the economics of various approaches to advanced biofuels, including bio-oil.
“Right now, bio-oil can be used as boiler fuel and even burned in some kinds of gas turbines,” says Robert Brown, director of the Bioeconomy Institute at Iowa State University who is leading the collaborative research on bio-oil. However, with further upgrading, bio-oil is suitable as a transportation fuel and could help displace petroleum products, Brown says.
Bio-oil is the liquid that comes out of a biomass conversion process called pyrolysis, according to Richard Bain, with the National Renewable Energy Laboratory, which is working with ISU on bio-oil research.
Pyrolysis is a thermal process that rapidly heats biomass in an oxygen-free environment to a carefully controlled temperature, and then very quickly cools the volatile products formed during the reaction. This procedure produces three products: a liquid, char, and gas. Pyrolysis has been a common tool in waste management for some time and is based on the idea of the chemical decomposition of organic materials by applying heat.
The energy-rich liquid from pyrolysis, or bio-oil, can be burned to produce heat and electricity or converted into transportation fuel at petroleum refineries. Many also see bio-oil as an intermediary to a number of higher-value chemicals, pharmaceuticals, and food additives.
Bio-oil has about 40% of the heating value of diesel, but can be used directly in diesel engines or gas turbines. Bio-oil also has a higher viscosity than diesel so it must be pre-heated to lower the viscosity.
While initial biomass sources for bio-oil will be wood waste and cellulosic plant materials, scientists are also interested in using pyrolysis to process poultry litter into bio-oil. Virginia Tech researchers recently announced that they are developing a portable pyrolysis unit that will create bio oil from poultry waste.
According to Foster Agblevor, Virginia Tech associate professor of biological systems engineering, more than 5.6 million tons of poultry litter are produced each year in the U.S. If Agblevor can translate his vision into reality, the litter could be reduced to char, fertilizer, gas and bio-oil.
“The type of poultry litter used will affect the amount and quality of the bio-oil produced and ultimately will impact the producer’s profitability,” Agblevor says. “Finding the right set of conditions for the poultry litter is key to the adaptation of this technology.”
