Sustainable High Density

Modern urban centers from Manhattan to Hong Kong now boast neighborhoods that house well over 100,000 people per square mile, while providing their inhabitants an excellent quality of life. As world civilization voluntarily and inexorably urbanizes, new megacities will be built everywhere. It is estimated that within the next few decades the number of megacities on earth – defined as an urbanized area with over 10 million inhabitants – will increase from around 20 today to over 400. So what innovations being pioneered today will enable cities like this to provide a high quality of life, and how will cities of such size and density reduce their vulnerability to economic or physical disruptions?

In a way, a megacity is antithetical to the notion of being “off-grid,” yet in important ways it is the megacity that needs to be as self sufficient as possible, since having 100,000 people per square mile (20,000 per square kilometer) means that any resource that needs to be imported, stored or removed is going to have to be handled in very high volumes. Therefore energy efficiency, waste management, as well as energy and water harvesting and treatment are technologies that are extremely important to the megacity – along with smart systems to interconnect all of them. So along with energy and water efficiency, harvesting and reuse, how else can a megacity exist relatively off-grid? Equally important is the closely related question of how can a megacity experience a postive balance of payments – supporting itself economically?

Cities could become food exporters.
(Image: VerticalFarm.com)

To explore this question beyond the usual suspects there are two evolving technologies (both are evolving, not emerging, because both have illustrious histories) that promise to transform megacities in important and very positive ways, one is high-rise agriculture, and the other is massive tunnelling systems.

It is common for the smart growth crowd to say “build up, not out,” but this misses two key points. First, of course, the smart growth advocates tend to forget that the smartest growth is unplanned. Centrally planned growth tends to actually promote sprawl, because those of us who don’t want to live in towers simply buy land and build homes on the far side of whatever “greenbelt” they manage to decree. But more on point, building up instead of out ignores building downwards as well. Some of the greatest urban gridlock ever seen has been ameliorated by tunnelling – anyone who tries to get to Logan Airport from downtown Boston during rush hour will have nothing but good things to say about the much maligned “big dig.” It’s too bad we don’t have more big digs – in the heart of urban centers we could put freeways and rail underground, and our cities could reach for the sky, and there would never be a traffic jam.

Tunnelling on a grand scale can seem mundane until you learn more about it – then you realize it is a fascinating field that is advancing at breakneck speed, incorporating new technology across multiple disciplines as fast as it becomes available. From GPS systems that allow a tunnelling machine to always know precisely where it is beneath the earth, to better cutting bits, to debris removal conveyers, to conveyers to bring forward shoring material, to worker shelter and control rooms, modern tunnelling machines can exceed a mile in length and cost billions to acquire and operate. The global leader in tunnelling systems is Herrenknecht AG. A good website that covers the world of tunnelling is tunnelmachines.com.

As the megacities of the future are built, tunnelling machines will play an integral part in endowing these cities with efficient transportation systems. Tunnelling underground to create utility conduits to transport water and energy will also be necessary in cities of ultra-high density. Using the volume of underground space to host much of the physical plant of megacities will make the surface areas far less congested, and far more pleasant for people. The underground systems of megacities can include large-scale water cisterns, or even enhanced geothermal power stations to extract power from the heat in the earth’s crust.

The imperative to build upwards is already a part of the new urban vision, but what about high-rise agriculture? The technology to grow food at extremely high volume indoors is already well understood – the Netherlands, for example, is a net food exporter in spite of being the most densely populated nation in Europe. But what the Dutch do using advanced hydroponics and lighting, in greenhouses that glow for miles across the reclaimed polders all year long, might instead take place on the stacked stories of a skyscraper.

One of the pioneers of high rise agriculture is Dickson Despommier, a professor at Columbia University and the founder of Vertical Farms LLC. Most of the technology to operate a vertical farm is already here, as well as much of the infrastructure. A properly designed vertical farm imports grey water (plenty of that in a mega-city) and pumps it to the top of the building, then allowing it to trickle downwards through hydroponic media on floor after floor. With mirrors and energy efficient lighting, along with daylight, a high-rise farm would probably consume, overall, less energy and water per calories grown than a greenhouse, since heating would be far more efficient in a multi-story structure. Despommier estimates a high rise farm on one city block (30 stories, 100,000 square feet per floor) could produce enough food to meet the needs of at least 10,000 people (possible much more, read “The Vertical Farm” .pdf, 2004). Every type of produce except for grains is potentially cost competitive to land-intensive traditional agriculture.

The implications of building upwards and downwards, employing novel technologies ranging from enhanced geothermal to high-rise farming, hold forth not only the oft-wished for promise of attracting humanity’s billions off the land and into densely populated megacities, but also the promise of cities that live nearly off the grid, cities that may, despite their magnitude, require very little from the rest of the world. Cities that might actually export power and food.


2 Responses to “Sustainable High Density”
  1. Alan Hoffman says:

    New Urban design is not an architectural style nor does it encourage heartless places because human individuality is embraced. These committees lend themselves easily to sustainability and energy efficiency. We will see more of them soon given Obama’s support for sustainable design. You can see one now at Osharavillage.com and Google “Obama Future Today”

  2. M S Haspels says:

    Forget about tunneling, automated vehicles should do the trick for goods, the Vertical Farms can clean waste water and use the nutrients out of it for the crops and more goods will be produced and recycled within the city because manufacturing technologies are become smaller. Tunneling is way too expensive and farfetched (foundations, pipes etc)

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