Although significant investments have been made in technologies for the production of ethanol from corn, biodiesel from soybean oil or canola oil, and more recently for the conversion of nonfood biomass feedstocks into ethanol and biodiesel, to date, the technologies for producing hydrocarbon fuels such as gasoline, diesel and jet fuel from biomass seem to have been overlooked. This will likely change, however, with recent reports of advancements in green gasoline production from a research group at the University of Massachusetts, Amherst. In addition, scientists and engineers at the Pacific Northwest National Laboratory in Washington State, in collaboration with researchers at UOP LLC, a developer and licenser of process technologies and catalysts and the National Renewable Energy Laboratory, are preparing to scale-up their approach to the production of green gasoline in the next year or two.
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“I think in the broadest sense, the significance of green gasoline is that it provides an alternative to ethanol,” explains Brent Shanks, a chemical engineer at Iowa State University who develops catalysts for the conversion of biomass to chemicals and fuels. “That’s significant partially because, looking forward to biofuels, the key question is what is the right biofuel? Ethanol and biodiesel have been initially selected because the technology is known. As we go forward talking about second-generation biofuels, it’s a broader picture we need to consider,” he says. “It is important as a country to have a portfolio of approaches for second-generation biofuels.”
The Washington workshop culminated in a recently released document, which was edited by George Huber, a chemical engineer at the University of Massachusetts, Amherst. The document provides a road map highlighting the novel process technologies being developed around the world for biofuels production. It is this transformational science that the workshop attendees believe will provide the foundation for future biorefineries.
In addition, the road map presents recommendations for research that will foster the development of a mature biofuels industry in the United States. The workshop and resulting road map focus on green hydrocarbon fuels because the workshop participants liken the growth of a biofuels industry as an accelerated version of the petroleum industry’s development, defined by intensive research and driven by innovations and tools available today. This stems from the chemical similarities between fuels currently derived from petroleum and those hydrocarbon fuels derived from biomass. Since the fuels are essentially the same at the molecular level, green hydrocarbon fuels have the same energy content as the fuels consumers are using today. These renewable fuels can be used in existing infrastructures such as engines and pipelines, and the production of green hydrocarbon fuels could also be integrated into existing petroleum refineries. It’s these characteristics that have piqued the interest of those in the oil industry. “All the big names are getting into this,” says Doug Elliott, a staff scientist at PNNL. “I think that’s a key change.”
It’s the infrastructure compatibility of green gasoline that is the primary draw. “These people are interested in using the facilities that they have to handle this type of material because it looks more like what they’re used to working with,” Elliott explains. For example, ConocoPhillips announced in the spring of last year that it would establish an eight-year, $22.5 million research program at Iowa State University to advance technologies for the production of biofuels. At the center of this research is the development of a process called fast pyrolysis,
In this process, solid biomass is injected into some kind of reactor, typically a fluidized bed. The feedstock is heated to temperatures ranging from 400 to 600 degrees Celsius (752 to 1,112 degrees Fahrenheit) for short periods of time, typically less than 2 seconds, followed by rapid cooling. The products of the reaction include gases, char and a liquid bio-oil. The latter consists of water, oxygen and thermally cracked pieces of cellulose, hemicellulose and lignin from the original feedstock.
Bio-oils are mixtures of more than 300 compounds that must be upgraded in a catalytic process to a liquid transportation fuel. This process of upgrading bio-oil to gasoline is not a new process. In fact, Don Stevens, a senior program manager at PNNL, has a jar of green gasoline in his office that was made in the mid-1980s that has yet to evaporate. “Some of the ideas like green gasoline have been around for awhile and progress was made years ago,” Stevens says. But cheap petroleum-based fossil fuels made the production of a biobased alternative cost prohibitive. “Fortunately, the capability underlying [green gasoline production] is still around,” he says. “These days it’s much more interesting.”
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