New conversion process turns biomass 'waste' into lucrative chemical products

Purdue's R.B. Wetherill Professor of Chemistry, holds a small vial containing results of a new catalytic process that can convert the lignin in wood into high-value chemical products for use in fragrances and flavoring.
Credit: Purdue University photo/Mark Simons

A new catalytic process is able to convert what was once considered biomass waste into lucrative chemical products that can be used in fragrances, flavorings or to create high-octane fuel for racecars and jets.

A team of researchers from Purdue University's Center for Direct Catalytic Conversion of Biomass to Biofuels, or C3Bio, has developed a process that uses a chemical catalyst and heat to spur reactions that convert lignin into valuable chemical commodities. Lignin is a tough and highly complex molecule that gives the plant cell wall its rigid structure.

Mahdi Abu-Omar, the R.B. Wetherill Professor of Chemistry and Professor of Chemical Engineering and associate director of C3Bio, led the team.

"We are able to take lignin -- which most biorefineries consider waste to be burned for its heat -- and turn it into high-value molecules that have applications in fragrance, flavoring and high-octane jet fuels," Abu-Omar said. "We can do this while simultaneously producing from the biomass lignin-free cellulose, which is the basis of ethanol and other liquid fuels. We do all of this in a one-step process."

Plant biomass is made up primarily of lignin and cellulose, a long chain of sugar molecules that is the bulk material of plant cell walls. In standard production of ethanol, enzymes are used to break down the biomass and release sugars. Yeast then feast on the sugars and create ethanol.

Lignin acts as a physical barrier that makes it difficult to extract sugars from biomass and acts as a chemical barrier that poisons the enzymes. Many refining processes include harsh pretreatment steps to break down and remove lignin, he said.

"Lignin is far more than just a tough barrier preventing us from getting the good stuff out of biomass, and we need to look at the problem differently," Abu-Omar said. "While lignin accounts for approximately 25 percent of the biomass by weight, it accounts for approximately 37 percent of the carbon in biomass. As a carbon source lignin can be very valuable, we just need a way to tap into it without jeopardizing the sugars we need for biofuels."

The Purdue team developed a process that starts with untreated chipped and milled wood from sustainable poplar, eucalyptus or birch trees. A catalyst is added to initiate and speed the desired chemical reactions, but is not consumed by them and can be recycled and used again. A solvent is added to the mix to help dissolve and loosen up the materials. The mixture is contained in a pressurized reactor and heated for several hours. The process breaks up the lignin molecules and results in lignin-free cellulose and a liquid stream that contains two additional chemical products, Abu-Omar said.

The liquid stream contains the solvent, which is easily evaporated and recycled, and two phenols, a class of aromatic hydrocarbon compounds used in perfumes and flavorings. A commonly used artificial vanilla flavoring is currently produced using a phenol that comes from petroleum, he said.

The team also developed an additional process that uses another catalyst to convert the two phenol products into high-octane hydrocarbon fuel suitable for use as drop-in gasoline. The fuel produced has a research octane rating greater than100, whereas the average gas we put into our cars has an octane rating in the eighties, he said.

The processes and resulting products are detailed in a paper published online in the Royal Society of Chemistry journal Green Chemistry. The U.S. Department of Energy funded the research.

In addition to Abu-Omar, co-authors include Trenton Parsell, a visiting scholar in the Department of Chemistry; chemical engineering graduate students Sara Yohe, John Degenstein, Emre Gencer, and Harshavardhan Choudhari; chemistry graduate students Ian Klein, Tiffany Jarrell, and Matt Hurt; agricultural and biological engineering graduate student Barron Hewetson; Jeong Im Kim, associate research scientist in biochemistry; Basudeb Saha, associate research scientist in chemistry; Richard Meilan, professor of forestry and natural reserouces; Nathan Mosier, associate professor of agricultural and biological engineering; Fabio Ribeiro, the R. Norris and Eleanor Shreve Professor of Chemical Engineering; W. Nicholas Delgass, the Maxine S. Nichols Emeritus Professor of Chemical Engineering; Clint Chapple, the head and distinguished professor of biochemistry; Hilkka I. Kenttamaa, professor of chemistry; and Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering.

The catalyst is expensive, and the team plans to further study efficient ways to recycle it, along with ways to scale up the entire process, Abu-Omar said.

"A biorefinery that focuses not only on ethanol, but on other products that can be made from the biomass is more efficient and profitable overall," he said. "It is possible that lignin could turn out to be more valuable than cellulose and could subsidize the production of ethanol from sustainable biomass."

The U.S. Department of Energy-funded C3Bio center is an Energy Frontier Research Center. It is part of Discovery Park's Energy Center and the Bindley Bioscience Center at Purdue.

Purdue Research Foundation has filed patent applications and launched a startup company, Spero Energy, which was founded by Abu-Omar.

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Source:  Purdue University

NASA's Fermi Mission brings deeper focus to thunderstorm gamma rays

New research merging Fermi data with information from ground-based radar and lightning networks shows that terrestrial gamma-ray flashes arise from an unexpected diversity of storms and may be more common than currently thought. Credit: NASA's Goddard Space Flight Center

Each day, thunderstorms around the world produce about a thousand quick bursts of gamma rays, some of the highest-energy light naturally found on Earth. By merging records of events seen by NASA's Fermi Gamma-ray Space Telescope with data from ground-based radar and lightning detectors, scientists have completed the most detailed analysis to date of the types of thunderstorms involved.

"Remarkably, we have found that any thunderstorm can produce gamma rays, even those that appear to be so weak a meteorologist wouldn't look twice at them," said Themis Chronis, who led the research at the University of Alabama in Huntsville (UAH).

The outbursts, called terrestrial gamma-ray flashes (TGFs), were discovered in 1992 by NASA's Compton Gamma-Ray Observatory, which operated until 2000. TGFs occur unpredictably and fleetingly, with durations less than a thousandth of a second, and remain poorly understood.
In late 2012, Fermi scientists employed new techniques that effectively upgraded the satellite's Gamma-ray Burst Monitor (GBM), making it 10 times more sensitive to TGFs and allowing it to record weak events that were overlooked before.

"As a result of our enhanced discovery rate, we were able to show that most TGFs also generate strong bursts of radio waves like those produced by lightning," said Michael Briggs, assistant director of the Center for Space Plasma and Aeronomic Research at UAH and a member of the GBM team.
Previously, TGF positions could be roughly estimated based on Fermi's location at the time of the event. The GBM can detect flashes within about 500 miles (800 kilometers), but this is too imprecise to definitively associate a TGF with a specific storm.

Ground-based lightning networks use radio data to pin down strike locations. The discovery of similar signals from TGFs meant that scientists could use the networks to determine which storms produce gamma-ray flashes, opening the door to a deeper understanding of the meteorology powering these extreme events.

Chronis, Briggs and their colleagues sifted through 2,279 TGFs detected by Fermi's GBM to derive a sample of nearly 900 events accurately located by the Total Lightning Network operated by Earth Networks in Germantown, Maryland, and the World Wide Lightning Location Network, a research collaboration run by the University of Washington in Seattle. These systems can pinpoint the location of lightning discharges -- and the corresponding signals from TGFs -- to within 6 miles (10 km) anywhere on the globe.

From this group, the team identified 24 TGFs that occurred within areas covered by Next Generation Weather Radar (NEXRAD) sites in Florida, Louisiana, Texas, Puerto Rico and Guam. For eight of these storms, the researchers obtained additional information about atmospheric conditions through sensor data collected by the Department of Atmospheric Science at the University of Wyoming in Laramie.

"All told, this study is our best look yet at TGF-producing storms, and it shows convincingly that storm intensity is not the key," said Chronis, who will present the findings Wed., Dec. 17, in an invited talk at the American Geophysical Union meeting in San Francisco. A paper describing the research has been submitted to the Bulletin of the American Meteorological Society.

Scientists suspect that TGFs arise from strong electric fields near the tops of thunderstorms. Updrafts and downdrafts within the storms force rain, snow and ice to collide and acquire electrical charge. Usually, positive charge accumulates in the upper part of the storm and negative charge accumulates below. When the storm's electrical field becomes so strong it breaks down the insulating properties of air, a lightning discharge occurs.

Under the right conditions, the upper part of an intracloud lightning bolt disrupts the storm's electric field in such a way that an avalanche of electrons surges upward at high speed. When these fast-moving electrons are deflected by air molecules, they emit gamma rays and create a TGF.
About 75 percent of lightning stays within the storm, and about 2,000 of these intracloud discharges occur for each TGF Fermi detects.

The new study confirms previous findings indicating that TGFs tend to occur near the highest parts of a thunderstorm, between about 7 and 9 miles (11 to 14 kilometers) high. "We suspect this isn't the full story," explained Briggs. "Lightning often occurs at lower altitudes and TGFs probably do too, but traveling the greater depth of air weakens the gamma rays so much the GBM can't detect them."
Based on current Fermi statistics, scientists estimate that some 1,100 TGFs occur each day, but the number may be much higher if low-altitude flashes are being missed.

While it is too early to draw conclusions, Chronis notes, there are a few hints that gamma-ray flashes may prefer storm areas where updrafts have weakened and the aging storm has become less organized. "Part of our ongoing research is to track these storms with NEXRAD radar to determine if we can relate TGFs to the thunderstorm life cycle," he said.

Video: https://www.youtube.com/watch?v=JgK4Ds_Sj6Q#t=66

Source: NASA/Goddard Space Flight Center