Just plant your seeds and add fish

But while the politicians and academics pontificate on the theory, in the back gardens of the United States people are tackling such concerns in a practical manner.

There's a sci-fi quality to Rob Torcellini's greenhouse in Eastford, Connecticut. And what is going on inside is either a glimpse at the future of food growing or a very strange hobby – possibly both.

Torcellini's greenhouse wouldn't look out of place on a wayward space station. But then, in a literal sense, Torcellini, a 41-year-old IT director has left earth – as in soil – far behind him.

What feeds his winter crop of lettuce is recirculating water from the 150-gallon fish tank and the waste generated by his 20 jumbo goldfish. Wastewater fertilises the 27 strawberry plants from last summer too. They occupy little storage boxes in a 7ft pipe. When the temperature rises in spring, he will plant the rest of the gravel containers with beans, peppers, tomatoes and cucumbers – all the things many other gardeners grow outside.

In here, though, the yields are out of this world. "We actually kept a tally of how many cherry tomatoes we grew," Torcellini said of last summer's crop. "And from one plant, it was 347."

It's all part of a home experiment he is conducting in a form of year-round, sustainable agriculture called aquaponics which combines hydroponics (or water-based planting) and aquaculture (fish cultivation) – and has recently attracted a zealous following of kitchen gardeners, futurists, tinkerers and environmentalists.

In the US, aquaponics is in its early stages but is increasing in popularity. Rebecca Nelson, 45, half of the company Nelson and Pade, publishes the Aquaponics Journal and sells aquaponics systems. While she refused to disclose exact sales figures, she estimates that there may be 800 to 1,200 aquaponics set-ups in American homes and perhaps another 1,000 bubbling away in school science classrooms.

Travis W Hughey, 49, provided one of the earliest textbooks on the subject and describes himself as an "agri-missionary" who hopes to help feed the developing world.

He came to aquaponics with little more than an unfinished biology degree and a background in yacht repair – a career that required him to be "a jack of all trades, and a master of every one of them".

The low-tech, low-cost design in his Barrel-Ponics Manual can be built out of three 55-gallon barrels, a pump, a wooden frame and some off-the-shelf hardware. One barrel, which sits on the ground, holds the fish. A second – split in half and filled with gravel – holds the plants. The final barrel, a storage or flush tank, perches above the other two like a toilet tank. The effluent-rich water that flows from one receptacle to the next is the life of the system, flooding the plants with nutrients and then trickling back into the fish tank.

From these rudiments, all manner of aquaponics systems can be built. Hughey has grown everything from radishes to a papaya tree in those barrels. His family could also eat the tilapia fish swimming around the 1,000-gallon in-ground plastic tank but he's saving them to use as breed stock.

There is something about aquaponics that seems to inspire this quirky blend of entrepreneurialism, environmentalism and survivalism. Proponents highlight the water shortages in farming areas such as the Central Valley in California – to say nothing of Africa.

Jack Rowland can imagine a day when aquaponics systems could be built into new apartment complexes and be fed by municipal waste and geothermal power.

In the meantime, he has started his own 1,200-gallon tilapia hatchery in his family's unfinished basement in Wappingers Falls, New York. He keeps the fish in black cattle troughs, which are sturdy and non-toxic.

Tilapia will tolerate crowding and will feast on your table scraps ("they're the ultimate waste disposal unit", Rowland says). But, being tropical by nature, they die in the cold.

One of the pools is called the dinner tank. It is here that Rowland condemns his tilapia to a five-day fast before they make their way to the frying pan. Tilapia, he said, do not deserve their bad reputation among cooks.

"Most of the tilapia sold (for the table] here was harvested months ago in China," he said. "It's like eating a fresh tomato versus what you buy in the grocery store."

This summer, he hopes to transfer his operation from a spot next to the washer and dryer to a 50ft-long hoop greenhouse.

Though Rowland spends perhaps an hour a night in the basement, looking for floaters and new spawn, he knows that no system is failsafe. Pumps break, heaters go haywire. The art of aquaponics is one of trial and error.

"My mentor in the tilapia world told me I really wouldn't be a master of tilapia until I killed at least a million fish," he said. "I'm not there yet."