Tuesday, March 16, 2010

COMPOSTABLE PLASTICS HAVE A SWEET ENDING

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Food packaging and other disposable plastic items could soon be composted at home along with organic waste thanks to a new sugar-based polymer.

The degradable polymer is made from sugars produced from the breakdown of lignocellulosic biomass, which comes from non-food crops such as fast-growing trees and grasses, or renewable biomass from agricultural or food waste.

It is being developed at Imperial College London by a team of Engineering and Physical Sciences Research Council scientists led by Dr Charlotte Williams. The search for greener plastics, especially for single use items such as food packaging, is the subject of significant research worldwide. “It’s spurred on not only from an environmental perspective, but also for economic and supply reasons,” explains Dr Williams.

Around 7% of worldwide oil and gas resources are consumed in plastics manufacture, with worldwide production exceeding 150 million tons per year. Almost 99% of plastics are formed from fossil fuels.

“Our key breakthrough was in finding a way of using a non-food crop to form a polymer, as there are ethical issues around using food sources in this way,” said Williams. Current biorenewable plastics use crops such as corn or sugar beet.

“For the plastic to be useful it had to be manufactured in large volumes, which was technically challenging. It took three-and-a-half years for us to hit a yield of around 80% in a low energy, low water use process,” explains Dr Williams.

This is significant as the leading biorenewable plastic, polylactide, is formed in a high energy process requiring large volumes of water. In addition, when it reaches the end of its life polylactide must be degraded in a high-temperature industrial facility.

In contrast, the oxygen-rich sugars in the new polymer allow it to absorb water and degrade to harmless products – meaning it can be tossed on the home compost heap and used to feed the garden.

Because the new polymer can be made from cheap materials or waste products it also stacks up economically compared to petrochemical-based plastics.

The polymer has a wide range of properties, laying the field open for a larger number of applications other than biorenewable plastic packaging. Its degradable properties make it ideal for specialised medical applications such tissue regeneration, stitches and drug delivery. The polymer has been shown to be non-toxic to cells and decomposes in the body creating harmless by-products.

The team – including commercial partner BioCeramic Therapeutics, which was set up by Professor Molly Stevens and colleagues at Imperial – are investigating ways of using the material as artificial scaffolds for tissue regeneration. They are also focusing on exploiting the degradable properties of the material to release drugs into the body in a controlled way.

Now the team is focused on developing the specific material characteristics needed for the packaging and medical areas.

“The development of the material is very promising and I’m optimistic that the technology could be in use within two to five years,” says Williams, who is already working with a number of commercial partners and is keen to engage others interested in the material.

(Photo: ICL)

Imperial College London

SCIENTISTS LOCATE APPARENT HYDROTHERMAL VENTS OFF ANTARCTICA

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Scientists at Columbia’s Lamont-Doherty Earth Observatory have found evidence of hydrothermal vents on the seafloor near Antarctica, formerly a blank spot on the map for researchers wanting to learn more about seafloor formation and the bizarre life forms drawn to these extreme environments.

Hydrothermal vents spew volcanically heated seawater from the planet’s underwater mountain ranges—the vast mid-ocean ridge system, where lava erupts and new crust forms. Chemicals dissolved in those vents influence ocean chemistry and sustain a complex web of organisms, much as sunlight does on land. In recent decades more than 220 vents have been discovered worldwide, but so far no one has looked for them in the rough and frigid waters off Antarctica.

From her lab in Palisades, N.Y., geochemist Gisela Winckler recently took up the search. By analyzing thousands of oceanographic measurements, she and her Lamont colleagues pinpointed six spots on the remote Pacific Antarctic Ridge, about 2,000 miles from New Zealand, the closest inhabited country, and 1,000 miles from the west coast of Antarctica, where they think vents are likely to be found. The sites are described in a paper published in the journal Geophysical Research Letters.

“Most of the deep ocean is like a desert, but these vents are oases of life and weirdness,” said Winckler. “The Pacific Antarctic ridge is one of the ridges we know least about. It would be fantastic if researchers were to dive to the seafloor to study the vents we believe are there.”

Two important facts helped the scientists isolate the hidden vents. First, the ocean is stratified with layers of lighter water sitting on top of layers of denser water. Second, when a seafloor vent erupts, it spews gases rich in rare helium-3, an isotope found in earth’s mantle and in the magma bubbling below the vent. As helium-3 disperses through the ocean, it mixes into a density layer and stays there, forming a plume that can stretch over thousands of kilometers.

The Lamont scientists were analyzing ocean-helium measurements to study how the deep ocean exchanges dissolved gases with the atmosphere when they came across a helium plume that looked out of place. It was in a southern portion of the Pacific Ocean, below a large and well-known helium plume coming off the East Pacific Rise, one of the best-studied vent regions on earth. But this mystery plume appeared too deep to have the same source.

Suspecting that it was coming from the Pacific Antarctic Ridge instead, the researchers compiled a detailed map of ocean-density layers in that region, using some 25,000 salinity, temperature and depth measurements. After locating the helium plume along a single density layer, they compared the layer to topographic maps of the Pacific Antarctic Ridge to figure out where the plume would intersect.

The sites they identified cover 340 miles of ridge line--the approximate distance between Manhattan and Richmond, Va.--or about 7 percent of the total 4,300 mile-ridge. This chain of volcanic mountains lies about three miles below the ocean surface, and its mile-high peaks are cut by steep canyons and fracture zones created as the sea floor spreads apart. It is a cold and lonely stretch of ocean, far from land or commercial shipping lanes.

“They haven’t found vents, but they’ve narrowed the places to look by quite a bit,” said Edward Baker, a vent expert at the National Oceanic and Atmospheric Administration.

Of course, finding vents in polar waters is not easy, even with a rough idea where to look. In 2007, Woods Hole Oceanographic Institution geophysicist Rob Reves-Sohn led a team of scientists to the Gakkel Ridge between Greenland and Siberia to look for vents detected six years earlier. Although they discovered regions where warm fluids appeared to be seeping from the seafloor, they failed to find the high-temperature, black smoker vents they had come for. In a pending paper, Sohn now says he has narrowed down the search to a 400-kilometer-square area where he expects to find seven new vents, including at least one black smoker.

The search for vents off Antarctica may be equally unpredictable, but the map produced by the Lamont scientists should greatly improve the odds of success, said Robert Newton, a Lamont oceanographer and study co-author. “You don’t have to land right on top of a vent to know it’s there,” he said. “You get a rich mineral soup coming out of these smokers—methane, iron, manganese, sulphur and many other minerals. Once you get within a few tens of kilometers, you can detect these other tracers.”

Since the discovery of the first hydrothermal vents in the late 1970s, scientists have searched for far-flung sites, in the hunt for new species and adaptive patterns that can shed light on how species evolved in different spots. Cindy Van Dover, a deep sea biologist and director of the Duke University Marine Laboratory, says she expects that new species will be found on the Pacific Antarctic Ridge, and that this region may hold important clues about how creatures vary between the Indian and Pacific Oceans, on either end.

“These vents are living laboratories,” said Van Dover, who was not involved in the study. “When we went to the Indian Ocean, we discovered the scaly-foot gastropod, a deep-sea snail whose foot is covered in armor made of iron sulfides. The military may be interested in studying the snail to develop a better armor. The adaptations found in these animals may have many other applications.”

(Photo: Woods Hole Oceanographic Institution)

Columbia University

ECOLOGICAL BALANCING ACT

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Phytoplankton are single-celled organisms that serve as the base of the marine food web and provide half the oxygen we breathe on Earth. They also play a key role in global climate change by removing carbon from the atmosphere and injecting it deep into the oceans.

Scientists study phytoplankton to understand how the tiny plants help transport elements like carbon through the environment. Although they understand much of what phytoplankton do, less is understood about why particular plankton live in particular environments and what maintains the diversity of phytoplankton.

Previous research has suggested that more diverse ecosystems may be more efficient at utilizing resources, meaning that the diversity of phytoplankton could be important for regulating the cycles of carbon and other elements in the ocean. But scientists need a better understanding of that diversity before they can understand how much carbon the ocean ultimately removes from the atmosphere.

Researchers from MIT’s cross-disciplinary Darwin Project, a collaboration between the Earth System Initiative (ESI) and the Computational and Systems Biology Initiative (CSBi) and funded by the Gordon and Betty Moore Foundation’s Marine Microbiology Initiative and NASA, have developed a computer model to simulate ecosystems in a virtual ocean, a model that could guide future field surveys of phytoplankton. They suggest that the diversity of phytoplankton species at a given location depends on the balance between the removal of species through competition for limited nutrient resources and their replacement by ocean currents, according to a paper published online Feb. 25 in Science Express.

In order to grow, phytoplankton need sunlight and nutrients like carbon, some of which comes from the carbon dioxide in the atmosphere. When phytoplankton die, some of their cells sink to the ocean floor, taking carbon away from the atmosphere and injecting it deep into the ocean through a process known as the “biological pump.” To understand the global scale of this process, scientists must learn more about the diversity of phytoplankton species.

“We feel this paper is a step toward understanding what the phytoplankton diversity is at different places in the ocean and what regulates that diversity,” said lead author Andrew D. Barton, a graduate student in the Department of Earth, Atmospheric and Planetary Sciences (EAPS).

Although future studies will have to make a more explicit link between phytoplankton diversity and the climate, Barton hopes that his group’s models could be used as a tool to inform future sampling surveys that try to map phytoplankton diversity in the ocean.

Barton and his colleagues used a computer model developed in 2007 by co-author Mick Follows, a senior research scientist in EAPS, to study the distribution of particular phytoplankton types, as well as to observe how phytoplankton help move different elements through the oceans.

To study these cycles, Barton’s team plugged information about the traits of nearly 80 phytoplankton species, such as how fast they grow and what temperature they prefer to live in, into the computer model, which also simulates the physical circulation and currents of the ocean. After the computer progressed the virtual ocean forward for a decade, certain patterns began to appear, with more species appearing in the warm tropics and Gulf Stream regions than at colder, higher latitudes.

Barton’s team then hypothesized why those patterns occur, taking into account the circulation of the ocean in different regions, as well as the fact that growth rates depend on changes in temperature, light and nutrient concentration. They conclude that the amount of species in a given location is based on how rapidly species are removed because of competition for limited resources, and the rate at which species are returned to that location by the ocean’s currents — a balance that is also affected by the nature of the environment.

In the tropics, seasonal variations are weak, and different species can coexist for long periods. But there is less diversity at higher latitudes, where the changing seasons vary the amount of light and nutrients that phytoplankton can consume throughout the year. Here, a few highly specialized phytoplankton rapidly outcompete all others during the strong spring blooms, and this effect outweighs the rate at which the ocean’s currents can return species to these latitudes.

Barton and his colleagues also explain that a relatively large variety of phytoplankton coexist in the Gulf Stream and similar currents that constantly move and mix different species from different regions. In this case, the variability of the environment doesn’t matter, because the intensity of the currents prevents more dominant species from outcompeting other species for food.

Princeton ecologist Simon Levin called the research “highly original and exciting” for scaling microscopic details of the ocean to macroscopic patterns by combining fluid dynamics, ecology and evolutionary biology data into one model. He also thinks the research will be useful for planning future studies where phytoplankton are collected.

Barton and his colleagues hope their interpretation will help inform future mapping surveys of the ocean by guiding oceanographers where to look for particular patterns in phytoplankton diversity. They need new field data to test and refine their hypotheses and are currently speaking to scientists at Woods Hole, MIT and the University of Hawaii about collecting data on upcoming long-distance scientific explorations in the Pacific Ocean.

Barton’s next step is to evaluate the diversity patterns using a very high resolution version of the current computer model to examine how the ocean’s complex range of structures — small eddies, currents and fronts — provide small habitats that could enhance diversity.

Future research should also examine how the processes of extinction and evolution help maintain the diversity patterns, he said.

(Photo: National Science Foundation)

Massachusetts Institute Of Technology

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