How low can you go?

We’re repeatedly advised to switch off electrical devices, like TVs and DVD players at the mains outlet rather than leaving them in standby mode, to turn to compact fluorescent bulbs and to turn them off when illumination is no longer necessary, to do our laundry at lower temperatures, to run the dishwasher only when it’s full, and to avoid using energy-hungry power showers. All those kilowatts add up to a lot of power wasted if we don’t.

According to a new study into energy use in the UK, by following this advice we might be reducing our carbon footprint a lot more than we thought. Conversely, those who don’t follow the advice might be wasting far more energy than the government thinks and so contributing more to carbon dioxide emissions and so anthropogenic global warming and climate change. Writing in the journal Energy Policy this month, Adam Hawkes, of the Grantham Institute for Climate Change at Imperial College London, has calculated that the figures used by government advisors to estimate the possible carbon dioxide reduction possible might be 60% too low.

Hawkes points out that power stations that supply electricity vary in their carbon dioxide emission rates, depending on the fuel they use: those that burn fossil fuels (coal, gas and oil) have higher emissions than those driven by nuclear power and wind. In general only the fossil fuel power stations are able to respond instantly to changes in electricity demand. He says that the government should keep track of changing carbon emission rates from power stations to ensure that policy decisions for reducing emissions are based on robust scientific evidence.

Hawkes used 60 million data points for electricity production each half-hour period by each power station in Great Britain from 2002 to 2009 and calculated the emissions for each different type of generator by examining government data showing their average annual fuel use. He then calculated emissions rates attributed to a small change in electricity demand from these two data sets.

SPT86-montalto-power-station (Credit: David Bradley)
Montalto power station (Credit: David Bradley)

His new study suggests that excluding power stations with low carbon emission rates, such as wind and nuclear power stations, and focusing on those that deal with fluctuating demand would give a more accurate emission figure. Hawkes’ calculations show that, 0.43 kilograms of carbon dioxide per kilowatt hour of electricity consumed is 60 percent lower than the actual rates observed between 2002 and 2009 (0.69 kilograms of carbon dioxide per kilowatt hour), meaning that policy studies are underestimating the impact of people reducing their electricity use.

“One way governments are trying to mitigate the effects of climate change is to encourage people to reduce their energy consumption and change the types of technologies they use in their homes,” Hawkes says. “However, the UK government currently informs its policy decisions based on an estimate that, according to my research, is lower than it should be.”

Links

Energy Policy, 2010, online

Tubes in space

Carbon nanotubes form in space but use a metal-free chemistry until now unavailable to chemists on Earth. The discovery is a surprising outcome of laboratory experiments designed by Joseph Nuth at NASA’s Goddard Space Flight Center, in Greenbelt, Maryland, and his colleagues. They were hoping to understand how carbon atoms are recycled in stellar nurseries, the regions of space where stars and planets are born, but the finding could have applications in nanotechnology, as well as help explain some characteristics of supernovae.

Writing in the journal Astrophys J Lett, Nuth and colleagues explain how astrochemistry makes carbon nanotubes without requiring a metal catalyst. Nanotubes are produced, they say, when graphite dust particles are exposed to a mixture of carbon monoxide and hydrogen gases, conditions that exist in interstellar space.

The finding corroborates the discovery of graphite whiskers, bigger than nano nanotubes, in three meteorites. The meteoric discovery hinted at why some supernovae appear dimmer and farther away than they ought to be based on calculations using current models. Nuth’s approach is a variation of a well-established way to produce gasoline or other liquid fuels from coal. It’s known as Fischer-Tropsch synthesis, and researchers suspect that it could have produced at least some of the simple carbon-based compounds in the early solar system. Nuth proposes that the nanotubes yielded by such reactions could be the key to the recycling of the carbon that gets released when carbon-rich grains are destroyed by supernova explosions.

Stellar Nursery
A stellar nursery could be home to carbon nanotube factories (Credit: NASA, http://apod.nasa.gov/apod/ap021102.html)

The structure of the carbon nanotubes produced by Nuth and colleagues was determined by materials scientist Yuki Kimura, of Tohoku University, Japan, using transmission electron microscopy. He observed particles on which the original smooth graphite gradually morphed into an unstructured region and finally to an area rich in tangled hair-like masses. A closer look with an even more powerful microscope showed that these tendrils were in fact cup-stacked carbon nanotubes, resembling a stack of disposable drinking cups with the bottoms removed. If further testing indicates that the new method is suitable for materials-science applications, it could supplement, or even replace, the familiar way of making nanotubes, explains Kimura.

Researchers might also now evaluate whether graphite whiskers absorb light. A positive result would lend credence to the proposition that the presence of these molecules in space affects the observations of some supernovae.

LINKS

Astrophys J Lett, 2010, 710, L98-L101

http://dx.doi.org/10.1088/2041-8205/710/1/L98

Catalytic troublemaker

Porous solid catalysts are a mainstay of the modern chemical industry, allowing reactions that would otherwise take an age to progress to be run much, much faster. One group of such catalysts are the zeolites and particularly important among them is one known as ZSM-5, an aluminosilicate material with an MFI structure. However, despite its attractions, ZSM-5 can behave badly because its chemical building blocks do not join together perfectly. This leads to chemical starting materials on which the catalyst is to act often becoming stuck before they can get into the reactive pores and be converted into product. Now, Dutch scientist Marianne Kox has discovered the nature of the miniscule deviations that can make ZSM-5 such a troublemaker.

Catalytic ZSM-5 isn't always on its best behaviour (Credit: Nature Materials/Weckhuysen et al)

Catalysts are essential to the production of a vast array of pharmaceutical drugs, agrochemicals, fuels and countless other chemical products that are made from simple starting materials. Kox and colleague Lukasz Karwacki, together with researchers at the Max Planck Institute for Coal Research in Mülheim an der Ruhr, Germany, ExxonMobil Chemical Europe Inc, Machelen, Belgium, the Centre for Nanoporous Materials, at the University of Manchester, UK, UOP LLC, a Honeywell Company, in Des Plaines, Illinois, USA, and Nicholas Copernicus University, Torun, Poland, have used a raft of spectroscopic techniques, on the micro scale to analyse the structure of zeolite ZSM-5 and have obtained spatial and time-resolved data on the three-dimensional interior of these porous materials. The data reveal the deviations from one porous unit to the next that can lead to reduced efficiency, catalytic poisoning, and unwanted chemical by-products.

Catalytic ZSM-5 (Credit: Nature Materials/Weckhuysen et al)

Kox is working as part of the Vici project run by Bert Weckhuysen, Professor of Inorganic Chemistry and Catalysis at Utrecht University in The Netherlands. Details of the research were published in Nature Materials. The team developed a new approach that correlates confocal fluorescence microscopy with focused ion beam–electron back-scatter diffraction, transmission electron microscopy lamelling and diffraction, atomic force microscopy and X-ray photoelectron spectroscopy to study a wide range of coffin-shaped zeolite crystals of differing shapes, sizes, structures, and chemical compositions.

The powerful combination of techniques demonstrates “a unified view on the morphology-dependent MFI-type [zeolite] intergrowth structures and provides evidence for the presence and nature of internal and outer-surface barriers for molecular diffusion,” the team say. “It has been found that internal-surface barriers originate not only from a 90° mismatch in structure and pore alignment but also from small angle differences of 0.5 to 2 degrees for particular crystal morphologies. Furthermore, outer-surface barriers seem to be composed of a silicalite outer crust with a thickness varying from 10 to 200 nanometres.”

LINKS

Nature Mater, 2009, 8, 959-965
http://dx.doi.org/10.1038/nmat2530

Bert Weckhuysen