· Win-win with biodegradable plastics from toxic waste
A biodegradable plastic made from toxic waste could solve pollution problems. The team from University College in Dublin have demonstrated that bacteria can use styrene, a toxic by-product of the polystyrene industry, to make a type of biodegradable plastic, polyhydroxyalkanoate, known as PHA.

Styrene is found in many types of industrial effluent, and in the United States alone accounts for 25 million kilogrammes (about 25,000 tons) of hazardous waste every year. Styrene causes lung irritation, muscle weakness, and affects the brain and nervous system in people and animals, so a method of disposing of it safely would have health as well as economic benefits.

"The current methods of dealing with waste styrene include underground injection, spreading it on land, or burning it in incinerators to generate energy, which results in toxic emissions," says Patrick Ward from the Department of Industrial Microbiology at University College, Dublin. "We all use plastics in our everyday lives from disposable drinking cups to car parts, so millions of tons are made, used and discarded every year. But the slow rate of degradation of polystyrene means that it can last thousands of years in our environment."

The scientists have discovered a strain of bacteria called Pseudomonas putida which can convert the dangerous petrochemical waste product, styrene, into a biodegradable plastic. The bacteria act as a small factory and storage unit, accumulating the plastic, PHA, inside themselves.

"We found that all of the available styrene was converted by the bacteria into plastic, and thus this process completely removes the pollutant," says Dr Kevin O' Connor, also from the Department of Industrial Microbiology at University College, Dublin. "The plastic made by the bacteria is an elastic type polymer, which would have a wide range of industrial and commercial uses such as medical implants, scaffolds for tissue engineering, wound management, drug carriers, plastic coating of cardboard and heat resistant plastic."

The University College team now hopes to improve the process by increasing the scale of the operation, and increasing the efficiency of the bacteria's action, to make commercially useful amounts of the PHA plastic. The conversion of styrene waste will be welcomed by industry, regulatory and environmental bodies since it removes a toxic waste material while generating a valuable, biodegradable and non-toxic plastic.

(Source: www.brightsurf.com)

· GROWing the next generation of water recycling plants
A vegetated rooftop recycling system has been developed that allows water to be used twice before it is flushed into the communal waste water system.

The Green Roof Water Recycling System (GROW) uses semi-aquatic plants to treat waste washing water, which can then be reused for activities such as flushing the toilet.

GROW is the brainchild of Chris Shirley-Smith, whose company Water Works UK is collaborating with Imperial College London and Cranfield University. The researchers are funded by the Engineering and Physical Sciences Research Council.

So-called grey water from washbasins, baths and showers is pumped up to the GROW system, which is constructed on the roof of an office or housing block. It consists of an inclined framework of interconnected horizontal troughs. Planted in these troughs are rows of specially chosen plants that gently cleanse the grey water. Trickling through the GROW framework, the plants' roots naturally take up the dissolved pollutants, leaving 'green water'. Green water is not drinkable and will be dyed with a vegetable colour to signify this, but it can be used to flush toilets or water the garden.

More than half the water used in the home and workplace does not need to be of drinkable quality yet it comes from the same pure source as our kitchen taps. Using GROW, much of the water that enters a building can be used twice before being placed into the national wastewater management system.

"We had to carefully choose which semi-aquatic plants to use. One of the most successful is water mint, whose roots have disinfectant qualities," says Professor David Butler, who oversees the project at Imperial College. The other plant species include the yellow flag iris, marsh marigold, and the common reed. They are chosen to be resistant to the pollutants they absorb. By planting more than one species, the engineers guard against an unusually dirty batch of water exceeding a particular species' tolerance level. Should one species die off, there will still be others there to continue the job until the dead plants can be replaced.

The beauty of the system is that it is not 'high-tech' in the traditional sense. "It does not require sophisticated maintenance, just tending, like any garden," says Butler.

The next aim for GROW is to see if it can be reduced in size to sit above a household water butt, making it serviceable for individual households. The team will also investigate whether the addition of an ultraviolet light can enhance the disinfection of the water. They hope to market GROW commercially in the second half of 2006.

GROW is one project in a much larger EPSRC-funded Sustainable Water Management programme (WaND) that Professor Butler oversees at Imperial. "Our overall aim is to contribute towards sustainable water management in new developments. We hope that GROW will be one of the tools that can help us achieve that goal," says Butler.

(Source: www.brightsurf.com)

· Sustainable nuclear energy moves a step closer
In future a new generation of nuclear reactors will create energy, while producing virtually no long-lasting nuclear waste, according to research conducted by Wilfred van Rooijen, who received his Delft University of Technology PhD degree based on this research subject.

Wilfred van Rooijen's research, conducted at the Reactor Institute Delft, focused on the nuclear fuel cycle and safety features of a Gas-cooled Fast Reactor (GFR), one of the so-called 'fourth generation' nuclear reactor designs. These designs have a sustainable character: they are economical in their use of nuclear fuel and are capable of rendering a great deal of their own nuclear waste harmless. The ability to actually build such reactors is however still in the very distant future.

The fourth generation GFR uses helium as a coolant at high temperatures. GFR's ultimate objective is to create a closed nuclear fuel cycle, in which only natural uranium is used as a raw material and in which the resulting waste consists of only nuclear fission products. Uranium and heavier isotopes, such as plutonium and americum, are recycled in the reactor and ultimately burned up (fissioned). In the reactors in use today, these heavy isotopes determine the long-term radioactivity of the nuclear waste. A closed nuclear fuel cycle therefore allows for maximum use of the raw materials, while at the same time substantially reducing the life-span of the waste.

This PhD research showed that it is possible to obtain a closed nuclear fuel cycle with a GFR. It also revealed that the GFR could use the waste materials of other light water reactors (LWR). The Gas-cooled Fast Reactor can therefore serve as an 'incinerator' of nuclear waste. To increase the GFR's safety, special elements have been designed to automatically shut down the reactor during incidents. Van Rooijen's research has shown that with these elements the reactor is capable of withstanding incidents without damage to the nuclear fuel.

(Source: www.brightsurf.com)