World water crisis spurs inventors
* Exhibition shows innovative technologies to secure water supply
* Some technologies already producing commercially, some early stage
LONDON, Sept 20 (Reuters) - Solutions such as fog catchers, seawater greenhouses and fuel cells powered by microscopic bacteria are on show to help secure water supply and food production as rising population and climate change put the world's natural resources under strain.
Water limits are close to being breached in several countries, while food output has to rise up to 100 percent by 2050 to sustain a world population seen growing by 35 percent from 6.9 billion to around 9 billion by that time, two U.N. reports have shown.
An exhibition at London's Science Museum starts as extreme measures to prevent global warming are being given more serious consideration by scientists as the world scrambles to curb climate change in the absence of a legally binding U.N. climate pact.
"Many of us don't realise how much fresh water goes into gorwing our food -- it takes 13 bath tubs to make a normal-sized chocolate bar," said Sarah Richardson, manager of the museum's "Water Wars" exhibition.
Among the projects on show is a British-designed greenhouse to create an oasis for crops in dry, windy places by exploiting the power of sun and wind to desalinate sea water.
It has a 2,500 square metre commercial-scale plant in the Australian outback which started to produce tomatoes last year.
The walls of the greenhouse are covered in cardboard which resembles honeycomb. The walls act as evaporators -- soaking up moisture carried by the wind from the sea and condensing it into fresh water to produce crops.
In another project, Cypriot engineers are designing the first concentrated solar plant to evaporate fresh water from seawater. They claim a small-scale facility could produce five million litres of water a day to replenish acquifers.
However, many experts are skeptical such projects can secure the massive sums of investment needed to produce huge amounts of fresh water.
Some schemes are too early-stage to become meaningful solutions any time soon, such as a fuel cell powered by millions of bacteria which aims to remove salt from sea water.
As the bugs munch away at wastewater, their metabolic processes produce charged particles which create a current to pull salt from sea water and generate electricity.
The fuel cell can currently only produce one teaspoon of fresh water every three hours and commercial-scale production is not foreseen for at least another 10 years. (Editing by William Hardy)