Generating ethanol from lignocellulose possible, but large cost reductions still needed

Ethanol can be blended with gasoline to reduce our dependency on fossil fuels. The last 15 years has seen a massive growth of so-called first-generation processes that use enzymes and bacteria to turn the starch and sugars in corn and sugarcane into ethanol. But corn and sugarcane are also important components of the human food web, so using them for ethanol production has the potential to affect the price and availability of these basic commodities.

On the other hand, lignocellulose materials are often hard to dispose of, but they are rich in sugars that can be fermented into ethanol following appropriate processing. "Not only is cellulose the most abundant polymer on Earth, it cannot be digested by humans, so using it for fuel production does not compete directly with food supplies," says the study's lead author Jamie Stephen, who works in the Department of Wood Science at the University of British Columbia in Vancouver, Canada. The race is on to commercialize this second generation ethanol.

Stephen's work focuses on the fact that the cost of building large scale ethanol-producing facilities will likely be higher for second generation ethanol compared to first generation technologies. One reason is that sources of lignocellulose may require significant and costly pre-treatment. "Researchers and companies are going to have to concentrate on reducing the cost of pretreatment and increasing the output of the digester in order to reduce the costs of the lignocellulose-to-ethanol process," says Stephen.

Another reason costs are higher is that lignocellulose is made of multiple kinds of sugar, while corn starch consists of pure glucose. Corn starch can be reduced to glucose with low-cost amylase enzymes, while pre-treated lignocellulose requires a cocktail of cellulase enzymes. Providing these enzymes is one of the major costs of the whole process, but you currently need 12 times more cellulase than amylase protein to generate the same amount of ethanol from woody biomass. "Despite much effort and progress over the last few years, the cost of using cellulase enzymes is still significantly higher than for amylase-based processes, and will need to be reduced substantially before lignocellulose starts to become competitive with corn and sugarcane as a feedstock," says Stephen.

Finally, while the input to sugarcane- and corn starch-based systems is fairly constant, the feedstocks that go into lignocellulose systems are much more variable. Different species of tree produce wood that has different properties, and waste paper and agricultural wastes will have many different types of material in them. To get maximum efficiency, each type of biomass needs to be processed under different conditions, which introduces another challenge for anyone wanting to make ethanol from these materials.

Overall Stephen believes we have a considerable way to go before second-generation ethanol production will be ready for commercialisation. "Production requires significant cost reductions and at least the same level of financial support that was given to the first-generation systems if second-generation ethanol is going to be fully competitive by 2020," says Stephen.

Provided by Wiley (news : web)

Physicists store antimatter atoms for 1,000 seconds -- and still counting

The ALPHA Collaboration, an international team of scientists working at CERN in Geneva, Switzerland, has created and stored a total of 309 antihydrogen atoms, some for up to 1,000 seconds (almost 17 minutes), with an indication of much longer storage time as well.

ALPHA announced in November, 2010, that they had succeeded in storing antimatter atoms for the first time ever, having captured 38 atoms of antihydrogen and storing each for a sixth of a second. In the weeks following, ALPHA continued to collect anti-atoms and hold them for longer and longer times.

Scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley, including Joel Fajans and Jonathan Wurtele of Berkeley Lab's Accelerator and Fusion Research Division (AFRD), both UC Berkeley physics professors, are members of the ALPHA Collaboration.

Says Fajans, "Perhaps the most important aspect of this result is that after just one second these antihydrogen atoms had surely already decayed to ground state. These were likely the first ground state anti-atoms ever made." Since almost all precision measurements require atoms in the ground state, ALPHA's achievement opens a path to new experiments with antimatter.

A principal component of ALPHA's atom trap is a superconducting octupole magnet proposed and prototyped in Berkeley Lab's AFRD. It takes ALPHA about 15 minutes to make and capture atoms of antihydrogen in their magnetic trap.

"So far, the only way we know whether we've caught an anti-atom is to turn off the magnet," says Fajans. "When the anti-atom hits the wall of the trap it annihilates, which tells us that we got one. In the beginning we were turning off our trap as soon as possible after each attempt to make anti-atoms, so as not to miss any."

Says Wurtele, "At first we needed to demonstrate that we could trap antihydrogen. Once we proved that, we started optimizing the system and made rapid progress, a real qualitative change."

Initially ALPHA caught only about one anti-atom in every 10 tries, but Fajans notes that at its best the ALPHA apparatus trapped one anti-atom with nearly every attempt.

Although the physical set-ups are different, ALPHA's ability to hold anti-atoms in a magnetic trap for 1,000 seconds, and presumably longer, compares well to the length of time ordinary atoms can be magnetically confined.

"A thousand seconds is more than enough time to perform measurements on a confined anti-atom," says Fajans. "For instance, it's enough time for the anti-atoms to interact with laser beams or microwaves." He jokes that, at CERN, "it's even enough time to go for coffee."

The ALPHA Collaboration not only made and stored the long-lived antihydrogen atoms, it was able to measure their energy distribution.

"It may not sound exciting, but it's the first experiment done on trapped antihydrogen atoms," Wurtele says. "This summer we're planning more experiments, with microwaves. Hopefully we will measure microwave-induced changes of the atomic state of the anti-atoms." With these and other experiments the ALPHA Collaboration aims to determine the properties of antihydrogen and measure matter-antimatter asymmetry with precision.

A program of upgrades is being planned that will allow experiments not possible with the current ALPHA apparatus. At present the experimenters don't have laser access to the trap. Lasers are essential for performing spectroscopy and for "cooling" the antihydrogen atoms (reducing their energy and slowing them down) to perform other experiments.

Fajans says, "We hope to have laser access by 2012. We're clearly ready to move to the next level."

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

ALPHA Collaboration: G. B. Andresen, M. D. Ashkezari, M. Baquero-Ruiz, W. Bertsche, P. D. Bowe, E. Butler, C. L. Cesar, M. Charlton, A. Deller, S. Eriksson, J. Fajans, T. Friesen, M. C. Fujiwara, D. R. Gill, A. Gutierrez, J. S. Hangst, W. N. Hardy, R. S. Hayano, M. E. Hayden, A. J. Humphries, R. Hydomako, S. Jonsell, S. L. Kemp, L. Kurchaninov, N. Madsen, S. Menary, P. Nolan, K. Olchanski, A. Olin, P. Pusa, C. O. Rasmussen, F. Robicheaux, E. Sarid, D. M. Silveira, C. So, J. W. Storey, R. I. Thompson, D. P. van der Werf, J. S. Wurtele, Y. Yamazaki. Confinement of antihydrogen for 1,000 seconds. Nature Physics, 2011; DOI: 10.1038/nphys2025