HOW DO we feed a burgeoning human population without trashing our environment? Build vertical farms in city high-rise buildings, according to Dickson Despommier.

Writing in the November edition of Scientific American, the Colombia University professor of public health and microbiology suggests that it will be less risky and more efficient to move some farming indoors, as close as possible to population centres.

The technology is available to build “vertical farms” in city high-rise buildings that could use a mix of aeroponics, hydroponics and drip irrigation to grow four-season crops, Professor Despommier wrote.

He calculates that a 30-storey high rise covering a city block would produce the equivalent of 970 ha of open farmland over the course of a year.

In a tightly controlled environment, crops would not be subject to the pest, disease, moisture or temperature stresses that occur in the field.

Because the “farms” would be in the heart of the population that consumes the produce, transport and fossil fuel use to deliver produce would be minimised.

In the US, there is an estimated 30 per cent wastage during transport of certain foods that would also be eliminated.

Prof. Despommier suggests that the farms could be powered by geothermal energy in some countries, solar energy in others, or by less orthodox means.

“One typical half-pound (220 grams) bowel movement contains 300 kilocalories of energy when incinerated in a bomb calorimeter,” he wrote.

“Extrapolating to New York’s eight million people, it is theoretically possible to derive as much as 100 million kilowatt-hours of electricity a year from bodily wastes alone, enough to run four, 30-story farms.”

The professor said there had been considerable interest in the idea from “developers, investors, mayors and city planners”.

But not, apparently, from farmers.


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