ONE of the really frustrating aspects of our planet is that while over two thirds of it is covered in water, it’s salty, so we can’t use it to grow all the extra food needed for a world population growing by 9,000 every hour – that’s another billion every fifteen years.

But a London theatre lighting engineer has developed the idea of a seawater greenhouse, which involves growing vegetables in a greenhouse by the sea.

It uses solar power to get the salt out of the water as well as providing electricity for all the pumping required, and the cooling necessary in an overheating greenhouse.

Already, experimental farms are proposed for coastal sites in Somalia, Qatar, Tenerife, the Cape Verde islands and Australia.

They all have good sunshine records, a generally dry climate and markets for the produce.

Sundrop Farm in South Australia, near Port Augusta, has an average temperature of almost 20 degrees, and less than 250mm (ten inches) of rain – all in all not the best conditions for growing vegetables.Solar panels heat oil circulating in sealed pipes to 160 degrees to produce the steam used to generate electricity for a small desalination plant that converts sea water into 10,000 litres of fresh water every day.

This power is also used to stop the greenhouse overheating by pumping sea water through filters to take heat out of the air as it evaporates, and this also keeps the moisture level high and the greenhouse well ventilated.

Nothing is left to chance as the greenhouse has its own pollinating bees, and the growing vegetables are generally free from disease and pests. It would be possible for the whole process to be organic though extra nutrients can be added, and there are plans to trial beans and pulses that would provide protein.

While this technical approach may not have wide appeal, no fossil fuels are needed, and on balance it’s a welcome carbon free development.