Tuesday, February 5, 2008

Creating Ethanol from Wood More Efficiently

Bacteria in termite guts could make ethanol from noncorn sources cheaper.

Special reserve: Shown above is a rare sample of ethanol created from wood chips using a new process. So far the alcohol is made a few bottles at a time, but in a couple of years millions of gallons could be available.
Credit: Karen T. Borchers/Mercury News

A type of bacteria that helps termites digest wood could be key to making ethanol cheaply from wood and grass. ZeaChem, a startup based in Menlo Park, CA, has developed a process based on this bacteria that can produce 50 percent more ethanol from a given amount of biomass than conventional processes can.

The company has demonstrated the method in a laboratory setting and is now drawing up plans for an ethanol plant that will produce about two million gallons of ethanol a year. Construction could begin as early as this year, says Dan Verser, a founder and vice president of research and development at ZeaChem. It is one of a growing number of biofuel companies seeking to make ethanol from noncorn sources, since corn requires large amounts of land, water, and energy to grow.

The process improves yield by making more efficient use of biomass than conventional techniques do. It begins, as do other techniques for making ethanol, with breaking down biomass into sugars. At this point, conventional processes use yeast to ferment the sugars into ethanol. But this process is wasteful: about a third of the carbon in the sugars never makes it into the fuel. Instead, it's released into the atmosphere as carbon dioxide. ZeaChem replaces yeast with a type of bacteria called Moorella thermoacetica, which can be found in a number of places in nature, including termite guts and the ruminant of cows, where it helps break down grass. Instead of making ethanol and carbon dioxide, the bacteria convert sugars into a component of vinegar called acetic acid, a process that releases no carbon dioxide.

To convert acetic acid into ethanol, ZeaChem turns to chemistry. First, the company's researchers convert the acid into a common solvent called ethyl acetate--something that chemists have long known how to do. The final step--making ethanol--requires adding energy to the system in the form of hydrogen. To get the hydrogen, ZeaChem uses material left over from the process that converts biomass into sugars. This material, called lignin, can be converted into a hydrogen-rich mixture of gases by heating it up under the right conditions--a process called gasification. The hydrogen is combined with ethyl acetate to make ethanol. The remaining gases in the mixture are fed back into the process to provide the energy needed for gasification, making use of material that otherwise would have gone to waste and eliminating the need to use fossil fuels. So far, the company has shown more than 40 percent better yield compared with conventional approaches, and it's working toward a theoretically possible improvement of 50 percent.

"It's a very innovative process," says James McMillan, a research scientist and group manager at the National Renewable Energy Laboratory, in Golden, CO. He says that it's important to get as much ethanol from the feedstock as possible, since the final cost of ethanol depends heavily on the cost of feedstock. Although ZeaChem's process is more complicated than methods used now, and building ethanol plants that use it will cost more, McMillan says that the improved yield could make up for these increased costs.


Tuning In to Nanotube Radio

Researchers have made analog electronics out of carbon nanotubes.

Transistor radio: A micrograph shows an array of four nanotube transistors.
Credit: John Rogers, UIUC
See a schematic and electromicrograph of the technology.
Listen to a recording of the radio using the nano radio.

Carbon nanotubes have long been a contender for future electronic devices because of their potential to scale down the size of components and their excellent electronic properties. But building practical circuitry out of carbon nanotubes has proved challenging. Now researchers at the University of Illinois at Urbana-Champaign report having made scalable radio-frequency analog electronics in which all of the transistor-based devices, including the antennas and amplifiers, are built out of nanotube transistors.

The goal is to establish carbon nanotubes as a realistic competitor with conventional analog electronics, says John Rogers, a professor of materials science and engineering at the University of Illinois. Rogers found a novel way to make transistors using parallel arrays of nanotubes. (See "A Breakthrough in Nanotube Transistors.") By way of demonstration of the ability to use the method in electronics, he has made a radio receiver out of which each of the active components is created from nanotubes. To test the electronics, the researchers say that they tuned the nanotube radio to a commercial station in Baltimore to hear the traffic report.

"It's a very significant advance," says Peter Burke, head of the nanotechnology group at the University of California, Irvine. "They have been able to make the first radio-frequency amplifier out of nanotubes."

Indeed, other groups have already demonstrated the use of single nanotubes in radio circuits. (See "The World's Smallest Radio.") "What we have done is a bit different," says Rogers. The previous research has involved using a single carbon nanotube to act as a radio receiver. "In our radios, every single active component is based on nanotubes, all the way up to the point where the headphones plug in," he says.

Employing single nanotubes in this way would not normally be feasible because of the relatively high currents used in analog circuits, such as amplifiers. To get around this, Rogers's nanotransistors consist of arrays of thousands of nanotubes in parallel, in such a way that they spread the current, while collectively behaving like a semiconductor material.

Rogers says that the fabrication method used to build the analog lends itself to current manufacturing processes. "With these arrays, we can build our devices, device arrays, and integrated circuits in wafer scale processing sequences that are fully compatible with established approaches to building semiconductor devices," says Rogers.

A crucial factor in making these transistors lies in Rogers's ability to grow the carbon nanotubes in such uniform arrays. But by growing the nanotubes on a single crystalline quartz substrate, using a standard chemical vapor deposition process, Rogers and his coworkers were able to fabricate "aligned arrays that are completely parallel," he says.

Once the arrays have been grown, Rogers makes a transistor using existing patterning techniques to lay source and drain electrodes over both of the ends of all the nanotubes, and by placing a gate across their collective width. "From that point on, the process is just like making silicon on insulator devices," says Rogers.

"As silicon transistors become smaller, inherent limitations become more critical," says Alex Zettl, a physicist at the University of California, Berkeley. "Nanotubes as a material are an exciting alternative material for forming extremely small, stable transistors," he says.

But while the original interest in nanotubes for electronics lay in their nanometer size, there has been an increasing amount of interest in their use for analog electronic devices, says Burke. There are now predictions that nanotubes will actually outperform conventional analog transistors, he says.

Rogers's radio is relatively big, with each transistor consisting of thousands of carbon nanotubes. But he says that there is plenty of room to scale them down, not least because there are relatively large gaps between some of the nanotubes. So it should be possible to pack them in more densely. "Ideally, you would want the nanotubes to be sitting right next to each other," Rogers says. He and his colleagues are now working on creating integrated circuits containing up to 100 of these transistors.


Internet at its choke points

Analyzing the Internet Collapse

Multiple fiber cuts to undersea cables show the fragility of the Internet at its choke points.

Cutting off communication: Wednesday's fiber cuts occurred about five miles away from Alexandria, killing connections between Europe and Egypt, the Middle East, and India.
Credit: Telegeography Research

When the Internet suddenly collapsed early last Wednesday across the Middle East and into India, it provided a stark reminder of how the Net's virtual spaces can still be held hostage to real-world events.

Almost simultaneously, two separate undersea fiber-optic cables connecting Europe with Egypt, and eventually with the Middle East and India, were cut. The precise cause remains unknown: experts initially said that ships' anchors, dragged by stormy weather across the sea floor, were the most likely culprit, but Egyptian authorities have said that no ships were in the region.

Whatever the cause, the effects were immediate. According to its telecommunications ministry, Egypt initially lost 70 percent of its connection to the outside Internet and 30 percent of service to its call-center industry, which depended less on the lines. Between 50 and 60 percent of India's Net outbound connectivity was similarly lost on the westbound route critical to the nation's burgeoning outsourcing industry.

"This [fiber path across the Mediterranean] is a choke point, which until recently was a very lightly trafficked route where there wasn't great need for cable," says Tim Strong, an analyst at telecommunications research firm Telegeography Research. "There are many new cables planned for the region, but as it happens, they're not in service yet."

Undersea cable damage is hardly rare--indeed, more than 50 repair operations were mounted in the Atlantic alone last year, according to marine cable repair company Global Marine Systems. But last week's breaks came at one of the world's bottlenecks, where Net traffic for whole regions is funneled along a single route.

This kind of damage is rarely such a deep concern in the United States and Europe. The Atlantic and Pacific Oceans are crisscrossed so completely with fast fiber networks that a break in one area typically has no significant effect. Net traffic simply uses one of many possible alternate destinations to reach its goal.

Not so with the route connecting Europe to Egypt, and from there to the Middle East. Today, just three major data cables stretch from Italy to Egypt and run down the Suez Canal, and from there to much of the Middle East. (A separate line connects Italy with Israel.) A serious cut here is immediately obvious across the region, and a double cut can be crippling.

The two damaged cables, both cut about five miles north of Alexandria, Egypt, are the most modern of the trio. One, owned by the U.K.-based Flag Telecom, a subsidiary of the India-based Reliance Group, stretches nearly 17,000 miles from Europe to China. The second cable, known as Sea-Me-We 4 and owned by a consortium of 15 different telecommunications companies, stretches from Spain to Singapore. Together, they have a capacity of close to 620 gigabits per second, according to Telegeography Research.

The one remaining cable traversing roughly this route is the older Sea-Me-We 3 cable, which has a capacity of 70 gigabits per second--considerably less than its newer rivals.

A third regional cable, also owned by Flag Telecom, was cut the morning of February 1 off the coast of Dubai, in an apparently unrelated event. This break has caused less trouble, since it is part of a Middle East loop that offers alternative routes for data traffic.

A map of the fiber-optic cables crossing the Mediterranean, connecting Europe with Egypt, the Middle East, and ultimately India. The Flag Telecom Europe-Asia and Sea-Me-We 4 lines were cut last week just north of Alexandria, Egypt.
Credit: Telegeography Research

The cause of the cuts in the two main broken cables remains somewhat mysterious. A spokesman for Flag Telecom said on Monday that the company would not speculate on the causes until the broken line has been examined. However, Egyptian telecommunications officials said on Sunday that no ships had crossed the site of the breaks in the 12 hours before or after the incidents on Wednesday. The site is also a "restricted area," further lessening the chances of a ship's responsibility, the ministry said.

The unexpected collapse in service forced Internet providers across the region to scramble for alternative connections, most using backup bandwidth sources under contract for just such an emergency. Many ISPs began switching traffic east instead of west. Data from India to Europe might thus first pass through East Asia, across the Pacific, through the United States, and across the Atlantic Ocean before reaching its destination. While slowing traffic, in some cases significantly, this at least allowed data to get through.

According to ISP Association of India secretary R. S. Perhar, service providers in his country adapted to the cuts relatively quickly. Traffic from business customers was given a top priority on networks, with consumer traffic taking second place. Three of the country's largest service providers weren't affected at all, since they weren't buying bandwidth from the Flag or Sea-Me-We 4 cables, he says.

Many other Indian companies had diversified their network connections following December 2006, when an earthquake off the coast of Taiwan severed seven major undersea cables that served India as well as East Asia. But some providers who had not acted as quickly found themselves cut off entirely, Perhar says.

"Most have done good network planning and made sure they get bandwidth from several service providers," he says. "But there are people who did not have redundancy in their networks."

Outsourcing companies also found themselves facing potential disruption. With so much outsourced work now being performed in India or elsewhere in the region, companies in the United States and Europe are increasingly dependent on these broken lines for their everyday business. But like the ISPs, the biggest outsourcing companies said that they relied on redundant connections to ensure the flow of data.

"We have planned for circumstances like these," says Nathan Linkon, a spokesman for Infosys, a large Bangalore-based outsourcing company. "We have diversity in path and providers, and we haven't lost any connectivity to our offices or customers."

With just two cables at issue, restoring service is expected to go more smoothly than did the 49-day process required after the Taiwan earthquake. Flag Telecom has told its customers that a repair ship that launched from Catania, Italy, will arrive and begin work today. The company said that Egyptian authorities are "expediting the permits" so that work can begin as soon as the ship arrives.

These repair operations have become fairly routine, with marine service companies on call around the world to launch a ship as quickly as possible when a nearby cable has been torn by a ship's anchor or fishing net, or, more unusually, by a natural event such as an earthquake.

A repair ship will typically take several days to reach the site of a break, says Stephen Scott, commercial manager for the U.K.-based Global Marine Systems, which is not involved in fixing this week's break.

A ship will locate the break in the line, sometimes by using a remote-controlled submarine device that can send signals up and down the cable, Scott says. The cable is then cut entirely at the break, and the little sub brings one half to the surface. Alternately, some operations simply use long grappling hooks to grab the cable.

Once the first half is brought to the surface, the crew splices on a long segment of replacement cable. The first half is let back to the sea floor; the other broken half is brought to the top, and the other end of the replacement cable is spliced on.

Unless the seas are rough, this double-splicing operation can take about 20 hours from start to finish, Scott says.

In the wake of the fiber breaks, Perhar says that his organization is encouraging ISPs and companies dependent on fast connections to continue diversifying their bandwidth sources as much as possible, and to lobby for new cable to be laid.

Telegeography Research counts at least four new fiber lines planned for the Europe-Egypt route over the next few years, including another by Flag Telecom, one by Telecom Egypt, another by the Egypt-based Orascom Telecom, and a fourth funded by the India-Middle East-Western Europe consortium of companies.

But even these will all use roughly the same route, says analyst Strong. That will keep this Mediterranean zone a "choke point" worth watching.

"With more cables, it's getting better over time," Strong says. "But there will still be a lack of physical, geographical redundancy. That is something of a concern."