One thing that annoys me, usually by way of articles being shared on facebook, is tales of a Grand New Way of doing things*, called vertical farming. We can finally stop using land for growing stuff, and get it all from a building down the street, no food miles and all that. Before ranting on about this, The Guardian already kills it for me in this feature, probably without reflecting on it at all.
Wheat, maize and rice – these things that provide the bulk of our
calories- will be very difficult to grow on a vertical farm because you
need to accumulate a massive biomass for those crops - you might expect
typically anything between 5 and 12 tonnes per hectare of grain from
something like wheat, but to do that you have to accumulate upwards of
20 tonnes per hectare of dry weight of plant. So it's the weight of the
plant. The crops that are likely to be grown are high-value nutritious
crops – like tomatoes, lettuces, green crops.
The first point is; these are crops growing in greenhouses already, very tried and tested stuff. So why don´t we already stack these crops in storeys and move them into the city? Simple, it´s not worth it to use higher value land, and lots of lots of energy, to grow this stuff in a town centre, even a suburb, when you can grow it out in the sticks and drive it to market. The building of the structures, labor and energy usage, is expensive enough that it is often cheaper (and according to reports, expends less CO2 in the process, for those who are concerned about this), to ship/fly in tomatoes from North Africa instead of growing it in a greenhouse in a temperate country like the UK.
In fact, the primary input to producing these crops is sunlight, and common sense tells us that stacking crop production in storeys, requires the same energy to be retrieved from elsewhere. Hey, maybe we can replace the "saved" land with PV-panels as an educational demonstration of the law of diminishing returns.
The second point is; the savings in land area are minimal. According to these figures, the total amount of "croppable" land in the UK is 6,3 million hectares. Out of these, 163.000 hectares, or 2,6%, is used for horticultural crops. Big whoop. These crops are high value, nice to have, can yield a lot per area, but provides very little in the way of what we actually need in the Maslowian sense. When the G calls it "nutritious crops", this just plays into the idea that we´re somehow beyond needing proteins and calories to live another day, and that humans can subsist on vitamins, antioxidants and fiber.
*I´m not saying that Grand New Ways of doing things can´t happen, it certainly will, but people often mistake visions of "what would be cool" with what works. There is something that could considerably reduce the use of land, energy and other inputs (although not nutrients, as they would have to be fed into the process) from producing food, which is in vitro meats. But I don´t really see that stuff being produced in Islington either.
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