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Singapore scientists have devised an environmentally friendly and efficient process to handle with the huge amount of food waste that the city state produces. The researchers from the National University of Singapore (NUS) found that a genetically modified yeast can convert fats in food waste to recover half its weight in butanol. Butanol is a type of alcohol that can be used as fuel or to make other products such as cosmetics and textiles. 

The green process also help to reduce the 600,000+ tonnes of food waste that would otherwise be incinerated in Singapore yearly. This will lower the greenhouse gases generated. The new method of recycling food waste produces about four times less carbon dioxide than incineration. It is also superior to by half to anaerobic digestion - a process in which micro-organisms are used to break down food waste into usable biogas. 

The NUS method involves blending the food waste and extracting the fats in it. The fats are then added that to the genetically engineered yeast in a bioreactor. The resulting butanol produced is then filtered out.

The genetic make up of the yeast is modified by inserting 10 extra genes into its cells. The yeast, Yarrowia lipolytica has the natural ability to process fats. The genetic modification allows the yeast to produce almost 300,000 tonnes of butanol from 600,000 tonnes of waste food.

Past attempts to process food waste using biological method were not efficient and financially viable because they attempted to convert all the waste to ethanol. This used more energy than they produced. 

The research project has taken three year and $1.2 million in funding from the National Environment Agency. The research is continuing to further cut down on the leftover residue by finding a way to convert it into compost.

In a separate research, scientists from another Singapore university, National Technological University (NTU) demonstrated a method to cut the mass of food waste by up to 90 percent. This is done by using enzymes to convert the food waste into glucose.  Then micro-organism is then used to convert the glucose into ethanol. This method is able to produce 270 gram of ethanol from 1 kilogram of dry food waste. Research is still on-going.