It's brunch time in the not-too-distant future. You're in your favourite cafe and you have a craving for pancakes.
You know they're delicious because you order them all the time: fluffy and light with a slightly carroty taste.
Hardly a health food, but at least they're easy on the environment — they're made with organic eggs and 100 per cent locally-sourced bacteria.
The bioreactor that produces the flour is only a block away.
Like many people, you're worried about the size of your carbon footprint, so it's good to know that none of the main ingredients had to be shipped or flown in.
The coffee is good too — from a boutique plantation in an old converted office block just down the road.
It's expensive, but it's worth paying a little more to make sure the produce you eat and drink is grown right here in the city.
Your friend orders the pork and fennel sausages with a side salad — from the rooftop farm above the cafe.
She often feels guilty about the amount of meat she consumes. But at least the pig she's eating was raised on micro-algae, not soybean. So, a small chunk of the Amazon is still standing because the trees in that area weren't cut down to make way for yet another enormous soya plantation.
Eating pancakes made from bacterial flour and animals raised on unicellular photosynthetic micro-organisms might seem a little out there, but these ideas are currently being explored by scientists as part of a new approach to farming called controlled environmental agriculture (CEA).
And CEA, some agricultural researchers argue, could be the best way of reducing the environmental destruction associated with modern farming, which is both land and resource intensive.
The veggie patch goes high-tech
CEA represents a small but growing dimension of agriculture.
It's attracting huge investment, particularly in the United States where venture capitalists see gains to be made in a high-tech process known as vertical farming.
Vertical farms look like a cross between a factory and a laboratory.
Plants are grown indoors on trays, often stacked up to 30 tiers high.
Everything about the indoor environment is governed by sensors and automation, but the crucial ingredient is the artificial lighting.
"All the vertical farms operating today are using a type of lighting called LEDs, which stands for light emitting diode," says Jeffrey Landau, the director of business development at Agritecture, an urban agriculture consultancy.
"Different types of crops prefer different types of lighting. So, your leafy greens, your vegetative crops prefer light towards the blue side of the spectrum.
"Whereas your fruiting and flowering crops, they will want something more along the red spectrum of lighting."
Each variety of plant has its own tailored lighting recipe, allowing them to photosynthesise for much longer periods of the day — up to 18 hours at a time.
In practical terms, that means more crop yields.
The major players, to date, have concentrated on producing perishable goods such as salad vegetables — crops that traditionally require large amounts of water.
But vertical farming expert Paul Gauthier believes even staples like potato and wheat could eventually be grown indoors.
"Everything is possible. I don't think there is anything in the vertical farm that we can't grow," he says.
"I was growing coffee trees inside a vertical farm.
"It's a question of which kind of design we have to make and what the economics are behind it."
Dr Gauthier, who now works for the New Jersey-based company Bowery Farming, admits both the capital and energy costs involved in vertical farming are "definitely huge".
But that needs to be put in context, he argues, because significant government subsidies have long been provided to traditional farming operations.
People in glass houses
Others aren't so convinced.
Viraj Puri sees the Silicon Valley-inspired approach adopted by companies like Bowery as unnecessarily high-tech.
"It has certainly attracted a tonne of investment, media attention, consumer interest, there's no doubt about it," he says.
"I still think the business models will require a path to profitability before it can start to attract more mainstream financing."
Mr Puri, the CEO and co-founder of Gotham Greens, operates five rooftop urban greenhouse facilities in New York and Chicago.
His approach to controlled environmental agriculture is to recast the classic Dutch greenhouse of an earlier age, but with 21st century modifications.
"These are glass and steel structures controlled by computers that are able to monitor climate 365 days of the year, 24 hours a day, and make smart adjustments, data-driven adjustments, in order to maximise crop productivity, efficiency, reduce production losses," Mr Puri says.
"They combine a lot of these advanced horticultural and engineering techniques that proponents of vertical farming espouse and promote."
And they also have the potential to achieve exponential crop yields.
"One can still get 50 times the productivity on certain types of crops. But one relies primarily on natural sunlight which is a free natural resource," Mr Puri says.
Next year, Gotham Greens is due to open a 2,800-square-metre facility just outside Denver, Colorado, as part of a $70 million capital expansion plan.
"Some of these greenhouses are the size of dozens of football fields, so these aren't backyard hoop houses but rather very sophisticated climate-controlled buildings," Mr Puri says,
And they can get even bigger.
A French company is currently constructing a roof-top greenhouse in the centre of Paris that will cover some 14,000 square metres when completed.
Like Bowery Farms, Gotham Greens sells itself on growing pesticide free crops, grown locally with very few transport miles.
"Urban farming is about bringing issues closer to large population centres," Mr Puri says.
"And telling the story of how agriculture is an enormous consumer of natural resources around the world and how this form of farming can play a significant role in a more sustainable future."
The substitution game
For Cambridge University's Asaf Tzachor, the solution to environmental degradation lies not just in rethinking how we grow, but what we grow.
The future of food that he envisages is busy fermenting away in a bio-reactor in Iceland.
The facility is run by a company called Algaennovation, which has been experimenting with the development of a new kind of animal food supplement made from microalgae.
Dr Tzachor estimates up to 85 per cent of the soybean produced globally each year is used to feed farm animals.
Soya farming in South America is identified by environmental agencies as a major cause of deforestation.
So, the idea is to simply substitute the microalgae for soya.
"Microalgae are very interesting. They are marine organisms, which means that they don't need freshwater, unlike soybean," Dr Tzachor says.
"And we don't have to cultivate them on terrestrial areas, so we can grow them within facilities, and these facilities can also be closed."
The savings on water alone would be significant, says Dr Tzachor.
He says experiments at Algaennovation's facility have so far been able to achieve between 200 and 250 times more biomass per litre of water than soybean farming.
The next stage of development is demonstrating that microalgae production can be done on a mass scale.
A similar approach is being undertaken by researchers in Finland, but their focus is on producing a supplement for human food rather than stock feed.
Pasi Vainikka, from the company Solar Foods, says his company has used a bio-reactor to produce an edible flour made from fermented bacteria.
"We have a fermenter, but we don't use yeast. We use a specific microbe that doesn't eat sugar," he says.
"So instead of sugar we introduce carbon dioxide and hydrogen, and these the microbe uses for energy and carbon instead of sugars to grow.
"Then we take the liquid out of the fermenter when the microbes grow and multiply and you end up with a dry powder."
The flour, called Solein, has a 65 per cent protein content, says Dr Vainikka, and can be used as a substitute for wheat flour or soya in everything from bread to protein drinks.
"The organism has carotenoids. When you taste it raw it has a bit of an umami (savoury) taste," he says.
"When you add it to pancakes, for example, it tastes as if it would have egg, and also a bit of carrot taste."
"The production cost, according to our estimations, is around $US5 per kilogram."
But that cost, says Dr Vainikka, could be expected to decrease as production begins to scale.
"We are about 10 times more environmentally friendly than plants and about 100 times better than animal-based proteins," he says.
"If we want to make a fundamentally more sustainable food system for the increasing population, we need to disconnect from agriculture, which usually means irrigation, use of pesticides and a lot of land use.
"So, when we disconnect from everything that has to do with these processes, the environmental benefits are huge."
Despite the promise offered by controlled environmental agriculture, Mr Puri cautions against seeing it as "panacea or a silver bullet" for the world's growing food demand issues.
"I think solutions are going to have to be varied and they have to be uniquely suited to their own geographical, economic, social and cultural contexts," he says.
"I think there's many different ways to farm sustainably and responsibly.
"Indoor farming techniques can certainly play a significant role for certain types of crops, high-value crops, crops that use a lot of water, crops that often have to be shipped in refrigerated trains, planes or trucks over great distances."
But the challenge is great. The United Nations estimates the world's population will increase to around 9.7 billion by 2050.
That's another 2 billion mouths to feed.