One for the road: Researchers develop biofuel from whisky waste

The message is clear. Whisky and driving is not a good mix. But rules are made to be broken and researchers at Edinburgh Napier University have managed to successfully marry the two, albeit as a fuel for the vehicle and not the driver. Researchers have taken two by-products of the whisky-making process and transformed them into an energy dense biofuel that doesn't require vehicles to undergo any modification prior to use.
The technology behind the development is said to have been inspired by a 100 year old process known as Acetone-Butanol-Ethanol fermentation, which was developed by chemist Chaim Weizmann (who also just happened to be Israel's first President). For the last couple of years, researchers at the Edinburgh Napier University's Biofuel Research Center have been tweaking and finely tuning the process using distilling by-products supplied from Diageo's Glenkinchie Distillery. Diageo's whisky brands include Johnny Walker, J&B, Talisker Single Malt and of course Glenkinchie.
Every year, Scotland's GBP4 billion (about US$6.2 billion) malt whisky industry produces around 1,600 million liters of pot ale – the liquid from the copper stills – and 187,000 tonnes of draff – the spent grains. The research project led by Professor Martin Tangney has managed to successfully convert these waste products into biobutanol.

Butanol is a four carbon alcohol which is said to give up to 30 percent more output power than ethanol and has a lower vapor pressure and higher flashpoint which makes it easier to handle. It's also less corrosive making it easier to transport and store, and whereas ethanol can only be blended with petrol, butanol can also be blended with diesel or biodiesel. Significantly, butanol can also be used as a stand-alone transportation fuel in ordinary vehicles without the need for special engine modification. As well as being used as a biofuel, the new biobutanol product can also be used to manufacture other renewable bio-chemicals, like acetone.
Professor Tangney said: "The EU has declared that biofuels should account for 10 per cent of total fuel sales by 2020. While some energy companies are growing crops specifically to generate biofuel, we are investigating excess materials such as whisky by-products to develop them. This is a more environmentally sustainable option and potentially offers new revenue on the back of one of Scotland's biggest industries."

Edinburgh Napier University has now filed a patent for the new biofuel and plans to form a company to take the new product into commercial production – next stop, the petrol pumps.

Making light work of LED droop

The drive to bring eco-friendly LED lighting into our homes is being stopped in its tracks by an embarrassing problem known as droop – the disappointing reduction in efficiency that happens when the light bulbs operate at the high power levels they need to shine at their brightest.

"Efficiency droop is one of the main obstacles to achieving cost-effective and high-efficiency LEDs," says Seong-Ju Park at the Gwangju Institute of Science and Technology (GIST) in South Korea. "Droop becomes a very important issue as LEDs expand into applications like [indoor] lighting where they operate at high currents."

For years, LED production has grown in tandem with the cellphone, providing the backlight for their displays. But manufacturers will have to tackle droop before high-power LEDs can hit the big time.

The cause of LED droop is disputed, making the solution to the problem far from clear – but now, Park and colleagues at GIST have teamed up with Samsung LED to prop up this flagging performance with an unconventional device design.

A standard LED has a surplus of electrons on one side and a dearth of electrons – or an abundance of electron "holes" – on the other. Plug the LED into a circuit, and the electrons and holes move towards each other, combine, and release energy as light.

Droop means that the proportion of the recombinations that produce light peaks at low electrical powers, with the record-holding prototype devices reaching about 250 lumens per watt. Raise the power to levels typically used for indoor lighting, though, and an increasing proportion of the electric current is lost as heat, so the efficiency drops below 100 lumens per watt.

A trap to catch an electron

The electrons and holes are caught in tiny traps called quantum wells, where they are more likely to collide and recombine. In commercial white LEDs, quantum wells are made of gallium nitride (GaN) surrounded by barriers on either side made from indium gallium nitride (InGaN).

But conventional manufacturing techniques simply juxtapose the InGaN and GaN layers, creating an abrupt interface that physically strains the semiconductor material and generates an electrical field, which Park's team suggest might cut the chances of electrons and holes combining and emitting light.

To test the idea, the researchers changed the nature of the interface between the well and its barrier by introducing the indium more gradually. That created a steady gradient between the barriers and the well. By smoothing the interface between these layers, they could reduce the strain and thus weaken the electric field surrounding the quantum wells.

When compared against a conventional design, the team's LED rapidly becomes 20 per cent more efficient as the power goes up, generating more light and less heat. While similarly raised efficiencies have been reported before, the Korean team's approach reaches these levels at much lower currents and then sustains them.

"The paper appears to be an interesting contribution to the wide-ranging debate on droop," comments Rachel Oliver from the Centre for Gallium Nitride at the University of Cambridge, UK, However, she warns that LED droop is a complicated issue and unlikely to have a single, simple solution. "To really solve this important problem will require more wide-ranging and systematic studies."

Hydrogen bonds are caught on camera

By affecting the way molecules bind to each other, hydrogen bonds are responsible for water's high boiling point, ice's propensity to float and DNA's signature double helix.

Now these life-enabling bonds – essentially the force of attraction between one molecule's slightly positively charged hydrogen atoms, and negatively charged areas on a neighbouring molecule – seem to have been captured on camera.

Individual atoms can be imaged using a scanning tunnelling microscope (STM). As its sharp-tipped probe scans a surface, the extent to which electrons "tunnel" between the tip and surface indicates changes in height caused by the presence of atoms.

In 2008, Stefan Tautz at the Jülich Research Centre in Germany and colleagues found that the resulting images became sharper if cold hydrogen is present between the tip and the surface.

Intricate detail

Now his team has shown that this allows hydrogen bonds to be imaged too. When they applied the technique to a sample of the flat organic molecule PTCDA, not only did the molecules show up in intricate detail, an electrical signal was also detected between them (coloured green in image), at exactly the locations where hydrogen bonds are present.

"We were absolutely stunned to see this," says Tautz. The next step is to discover what is causing the phenomenon. "It's an open question, and I don't want to speculate," he adds.

Whatever that turns out to be, the imaging technique could have exciting applications. "The images show remarkable intramolecular resolution and greatly advance the investigation of molecular monolayer structures," says Leo Gross, a surface chemist from IBM Research in Zurich, Switzerland.

Designer nanopores

Peter Sloan, a physicist at the University of Birmingham, UK, says that the ability to image hydrogen bonds could, amongst other things, aid the construction of "designer nanopores". These are customisable gaps between self-assembled molecules that are held together by hydrogen bonds, and can enhance catalysis.

"The trick is how to design the self-assembled layer," he says. "Being able to see the hydrogen bonds between molecules will give a better understanding of the 2D bonding and hence allow better, more complex self-assembled structures to be designed and made."

STM only works on flat surfaces, so imaging the hydrogen bonds between more complex, three-dimensional molecules like proteins is not yet possible.

Green machine: Tackling the plastic menace

Plastic can take hundreds of years to degrade, so bottles and bags can be a danger to wildlife, strangling birds, mammals and fish, and soaking up toxic chemicals from seawater that can poison any creatures that swallow them.

What's more, plastic is expensive to recycle and requires a significant energy outlay, particularly in sorting and separating the different polymers that may be present.

Mixed plastic

Now Vilas Ganpat Pol at the Argonne National Laboratory in Illinois has developed a technique to convert a mixture of waste plastics into micro-spheres of a form of carbon called carbon black. The micro-spheres can be used in paints, lubricants and tyres, and even incorporated into the anodes of lithium-ion batteries.

To create the spheres, Pol melted a mixture of plastics in a reactor at 700 °C. At this temperature, the pressure in the reactor reaches 34 atmospheres, helping to break down the bonds between the hydrogen and carbon atoms in the polymer chains. The hydrogen gas is siphoned off, leaving behind carbon micro-spheres up to 10 micrometres in diameter (Environmental Science and Technology, DOI: 10.1021/es100243u).

Pol recently used a similar process to convert plastic waste into carbon nanotubes. However, this required the use of a relatively costly cobalt acetate catalyst, which could make the process prohibitively expensive if scaled up. The new technique requires no catalyst at all, says Pol.

Geoffrey Mitchell, a material scientist at the University of Reading in the UK, says the fact that the process uses no catalyst is a major plus, and if the technique can be used to recycle the growing mountain of low-value, mixed plastic waste, it could have a rosy future.

Self-destruct

Meanwhile, Scott Phillips and Wanji Seo at Pennsylvania State University in University Park have developed self-destructing plastics that could lead to packaging that is more easily recycled and friendlier to wildlife. Working with the polymer poly(phthalaldehyde), the team attached one of two chemical end groups, or "triggers" – either a silyl ether or an allyl ether – to each phthalaldehyde building block.

When a square of the polymer was exposed at room temperature to fluoride ions, the central section, where molecules were capped with the silyl ether, underwent rapid depolymerisation and broke down. Those sections capped with the allyl ether remained unchanged (Journal of the American Chemical Society, DOI: 10.1021/ja104420k).

The technique could be modified to develop plastic products that quickly degrade when exposed to triggers in the environment, he says. If a bag made of the right plastic reaches the ocean, for example, microbial enzymes in the water would make the material depolymerise and "the bag just disappears", Phillips says.

By capping all the polymer sections with an end group that responds to a certain chemical, the technique could also be used as a low-energy method for recycling plastic waste, says Phillips. The resulting monomers would have to be re-polymerised to create a new plastic, but this may prove cheaper than separating different polymers before recycling can begin, he says.

Smart materials

So far the team has developed polymers with end groups that react with fluoride ions, palladium and hydrogen peroxide, and they are also hoping to develop polymers that respond to enzymes, he says.

The team cautions that the research is still at the proof-of-concept stage. Work remains to be done to find polymers that break down into substances that are more environmentally friendly than phthalaldehyde. Another problem is that the polymers they have so far made are sensitive to acidity and need to be more stable to be usable.