The Future of Food on Urban Rooftops | Hacker News Reader

The Future of Food on Urban Rooftops

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58 pointssharp1144 comments

Conventional wisdom says each person requires ~1 acre (43k sq-ft) to source enough foodstuff for themselves.

With two people per 1k sq-ft apartment... you need ~100-fold improvement over the conventional wisdom to get full 100% sustainability. So let's assume you can magically get 10x gains in "land use" efficiency, and that you can stack those units 10 levels high (piping 1/10 of the 1kW/m^2 solar incidence to each level). But herein lies the rub: Urban density exceeds 2 people per 1k sq-ft of building rooftop area. So 100% rooftop sustainability is probably a no go.

Of course something is better than nothing (is it truly better than rooftop solar?), but it's worth pointing out that it can't be a panacea.

From what I recall reading some of the newer indoor hydro systems (plus LED) were getting greater than 20x increases (I think the lettuce/basil warehouse in Japan was getting over 60 heads of lettuce per square foot in comparison to traditional 3 per square foot in standardized farming). Perhaps by combining some of the different newer technologies they'll get the orders of magnitude of differences.

So why not use these techniques where land is cheap instead of on expensive urban rooftops?

Part of the thought was to also reduce transport cost. So if you have effectively the harvest and distribution localized one would reduce footprint in other ways.

That being said I'm not saying "expensive urban rooftops" are where we should be doing this. I was simply suggesting there are other changes afoot that are, for example, increasing yield. Any location will have pros on cons such as locality, cost, infrastructure, space reuse, etc.

Transport costs (in $ and CO2) are a rounding error compared to the cost of other inputs in food production.

Transportation has a large impact on the varieties and quality of food available.

Excessive handling creates waste and even drives your shopping habits; damaged fruits and vegetables don't last as long on the shelf so you have to pursue 'fresh' food regularly. Growers choose varieties based on transportation before taste or health.

It's not uncommon for someone harvesting their own root vegetables or apples to store one season's harvest for most of the year (my grandfather advocates a wooden barrel filled with sand). Almonds, and other nuts, are only harvested once a year and stored for distribution to meet demand.

In the US, modern perceived limits of 'fresh' food and expiration are greatly exaggerated, driven by the abundance of inferior product.

Seems like it'd be easier to improve upon that transportation bottleneck instead of something as drastic as restructuring the whole system and growing in urban areas.

Seems like it would be harder to re-engineer food transportation to be virtually shock-free. You'd have to revolutionize all packaging, sorting, loading and transport for each product.

Even handling when picking has an impact on shelf life; field workers aren't encouraged to be lax with their time.

As opposed to the alternative, where you walk a few steps to your garden and pick, sort, pack, transport, unpack a few minutes per day yourself.

A lot of the waste (at least from produce) comes from every step of the supply chain loosing product to buying to much or letting it sit to long. In theory, growing on a nearby roof could force people to grow only what they are going to use.

Is this 1 acre per person per year?

You don't need a new acre next year, so the units work out for 1 acre/person.

Not all food is equal. Most of the acre (~4k m²) is needed for high energy crops like wheat or rice. It's pretty efficient to transport those into the cities. They can be stored pretty long and are pretty robust for transport. They're also pretty low price. Vegetables and berries are way more interesting as they're the opposite of all those factors.

What's wrong with growing vegetables and berries outside of cities in greenhouses?

They store shorter and lose a lot more nutrition in transit. They are more expensive to harvest but are more caloric dense in a given area. Its why raspberries are like 5 dollars a pound but bananas are 50 cents. One has a much longer shelf life.

But driving from the outskirts of a city to the inside, is just a 1 hour journey.

For caloric sufficiency, you're probably growing sweet potato or potato, at 70 Mcal/ha-day and 54 Mcal/ha-day, respectively. For a 2 Mcal/person-day diet, that's a minimum of 0.03 ha/person, or about 0.07 acre/person eating sweet potato. For potato, 0.04 ha/person, or 0.09 acre/person.

(http://www.fao.org/docrep/t0207e/T0207E04.htm)

Assuming at minimum that hydroponics provides 2.5x normal yield, and aeroponics 3.5x normal yield, one person eating exclusively aeroponically grown sweet potato would need 880 sq.ft. dedicated grow area, or 1.75x the example's (500/person) apartment floor area. If you can stack 4 levels of plants on one floor, that's still 1/3 of all building volume that would have to be occupied by growing plants.

Bear in mind that 2 Mcal/person-day is only enough to sustain children and little old ladies.

So ultralocal farming is probably not going to meet 100% of the needs of a building's residents without some extreme change in the way we design residential buildings. What you really want to grow on your roof is flavorful, nutrient-dense foods that are not quite durable enough for long-distance shipping. Then you ship the durable, bruise-resistant commodity staples from actual farms.

You eat your potatoes shipped in from the farm garnished with fresh green onion from your rooftop. You get your durum noodles from elsewhere, and eat it with sauce made from your rooftop tomatoes and herbs. Truck in the dry solid foods from far away, and grow the wet squishy foods as close as you can to your plate.

Aquaponics proponents rarely mention that you have to feed the fish. The fish are essentially filters that reduce other matter (mostly other fish) into nitrates. An efficient system would remove these inefficient filters and add nitrates directly to the soil.

Yes, you can eat the fish. But it takes 240 days to raise (feed) a tilapia to 1 lb of weight. There are cheaper and faster sources of protein. For example, soy beans take 45-100 days and yield .25lb of pods per plant.

Aquaponics critics rarely mention that you can often close much (though not all) of your production loop by feeding the waste products from the final produce back to the fish. And with tilapia (and to a lesser extent catfish), feed sources are trending in the direction of insect meal, which has a super efficient protein conversion rate.

Soy is probably more efficient, but soy is not fish and soy does not promote the healthy growth of other specialty crops like lettuce etc.

But, if you have a study that talks about the efficiency of nitrogen added directly versus the nitrogen that comes from the fish, or how it differs, I would be super curious to read it.

I'm Jason Green, CEO at Edenworks. And aquaponics evangelist. Here's why we think aquaponics is the best solution to global protein (and vegetable) production.

Tilapia are protein producing machines. They convert 1.1-1.3 lbs of feed to 1 lbs of protein in 9 months (some factors like temperature, feed rate at different stages of life, and other things affect this ratio). But here's the real kicker--by providing the nitrogen that crops need, the crops can then turn CO2 into into calories via photosynthesis. Super high quality produce becomes the extremely valuable byproduct, effectively, of aquacultured seafood.

From a global net energy perspective, this is huge. Where do you think that nitrate fertilizer for soybeans is coming from? The Haber-Bosch process is crazy energy expensive. Growing soybeans for protein also has huge environmental costs--see deforestation in Brazil for details. 80% of cultivable land on earth is already in use, but food production needs to increase by 70% by 2050. Protein production will need to double due to the rising global middle class. And that middle class wants fish.

On top of all that, there's the fact that people don't want to eat just soybeans for protein. There's now more seafood consumed globally than beef cattle. By 2030, 62% of all seafood will be aquacultured, and there are some suggestions that most of the wild seafood species we know will be either extinct or heavily depleted.

Aquaponics is great from a numbers perspective. But so is Soylent...

Myself, and other conscious humans, conscious of the consciousness in animals, are concerned about quality of life (this is not the same thing as Veganism).

One example of a solution I deem unacceptable is raising rabbits for meat in stacked cages in an urban garage. (This has been advocated numerous times among various alternative food groups and I have read personal accounts of it's practice.)

How are 4^3 IBC tank 'cages' any different?

This has the potential to be the next theoretically-sterile factory farming failure, or a thriving, balanced ecosystem.

That's one thing I like about the idea of producing protein-rich food by the methods described in the article: it has the potential to cut down on the perceived need to subject caged farm animals to a lifetime of torture.

Excellent reply. The argument that animal protein production is more inefficient than directly eating the plant matter fed to the animal ignores the symbiotic relationship between plants and animals. Our extreme dependence on oil-based energy has tricked us into thinking that agriculture is sustainable without the use of animals. Of course, modern CAFOs are horribly wasteful as well, but that doesn't mean the plant/animal symbiosis isn't vital to the whole process.

All very nicely illustrated by your work.

Central London now has residential prices per sq foot from about £1K-£5k+ ($1.5K-$7.6K+) - roof space is often the most expensive (read penthouse) and suitable roofs sparse (at least in London).

How are you planning to find suitable space / scale in such conditions?

I don't understand some of your claims:

> They convert 1.1-1.3 lbs of feed to 1 lbs of protein in 9 months

They eat 1.1--1.3 lbs of food each month during 9 months, that is 9x1.1 -- 9x1.3 = 9.9 -- 11.7 lbs in total and produce 1 lbs of protein? Or the eat in total only 1.1--1.3 lb of food during the 9 months an produce 1 lbs of protein?

> But here's the real kicker--by providing the nitrogen that crops need

The fishes don't fixate nitrogen. They can "free" some nitrogen compounds in their food, but the nitrogen compounds have to come from somewhere. IIRC only some bacteria can fixate nitrogen naturally, (i.e. transform some unuseful nitrogen from the air into useful nitrogen compounds, that may be used to build proteins). Some plants, like soy, are good host for these bacteria, but I never heard that fishes have a similar symbiotic relation.

You're losing a lot (if not all) of the efficiencies of growing outside urban centers. The efficient distribution and consumption of irrigation water and fertilizer is more of a cost ($ & CO2) than the final transportation of food to consumers. This is likely feel-good solution that produces great food, but not net savings to consumers or society.

Aquaponics uses much less water than traditional agriculture. And the plants don't require as much (any?) fertilizer because of the fish.

And if people can pick their own vegetables, or pick them and sell/use them the same day, extremely locally, then you can select for taste instead of for transportation resilience.

It's well beyond feel-good.

Possibly as or more importantly, you can pick only what you need. A huge fraction of the food produced today is simply thrown away.

On top of that just picture most of today's people. "Well I'll take 10 of these tomatos and sell 8 of them! Muahah!"

Also roofed in gardens don't need pesticides...

You have clearly never dealt with a spider mite invasion.

They. Are. Everywhere.

They routine infest indoor houseplants, even in places you wouldn't expect. They'd find their way into a roof garden. And because most predators require a wider range than most prey, there may not be as many natural predators available.

Commercial greenhouse growers definitely try to isolate their plants from invasion, but still rely on pest control when the inevitable happens.

http://www.amazon.com/000-Live-Adult-Predatory-Mites/dp/B00I...

Predatory mites work fine if other mites are the only problem. They aren't particularly expensive either.

But yes, you can't use natural predators. You basically need to introduce them, let them do their jobs, and then most of the predators will die once the problem is controlled for.

But give its a $50 problem, its not a very expensive problem and on par with pesticide costs.

Consumption of irrigated water actually plummets with aquaponics (article cites 90% less water use), and, depending on the system, may not even need any fertilizer at all since the fish manure is circulated. You still have to feed the fish, true, but often that is supplemented with byproducts of the final produce production and is not as environmentally damaging as artificially produced nitrogen fertilizers (agriculture standard) anyways.

So, quite frankly, your statement that the efficient distribution of water is fertilizer is more is just wrong.

I'm not saying the tech is perfect or that it can't improve, but if even a fraction of the research dollars were put into this as is put into traditional/industrial research and development, I think aquaponics (especially when designed vertically) will outpace it easily.

I will note that this isn't true for many staple crops like corn, soy, or wheat. But that's not the point. You would need to compare specialty crop production, not commodity crop production.

This makes a tacit assumption about roof loading, which, by default, cannot support the load of an aquaponics installation (the logical choice). The ability to source some greens locally is useful, but as many have pointed out the win comes when you can locally source something like rice or beans. The water requirements for rice make it especially heavy on a per square foot basis. The folks in Watsonville [1] were trying it on flat ground first, it doesn't seem they were successful [2]

[1] http://www.santacruzsentinel.com/general-news/20130810/futur...

[2] http://www.viridisaquaponics.com/

Jason here, CEO at Edenworks.

Roof load is a question we get a lot, and it turns out not to be a dealbreaker if you can distribute weight on the building's columns effectively. Our next greenhouse will be ~ 110 lbs/s.f., which is heavy but nothing a little dunnage can't deal with. On a side note, a research team at Columbia conducted this awesome study showing there's over 5,000 acres of rooftop space feasible for urban farming in NYC (also recommended for any ArcGIS fans): http://urbandesignlab.columbia.edu/files/2015/04/4_urban_agr...

Regarding grains and legumes, you're right and I wouldn't recommend rooftop aquaponics for it - you simply need too much land. I do believe however that urban aquaponics can play a bigger role in supporting a growing, global middle class, which is consuming more vegetables and protein and is especially sensitive to food safety in some regions.

This article is about much larger scale stuff but it's interesting timing since we're about to put a roof deck on our townhouse (flat roof) and I've been researching some of the various "DIY EarthBox" plans out there.

My goal isn't so much to become self-sustaining by starting a rooftop farm but we'll have this big, flat, sunny area and I'm thinking if I put these or some other type of quality container garden around the perimeter, I can have a bunch of fresh vegetables during a good portion of the year and also make it feel a little more like a garden than just a hot, sunny, wooden platform in the middle of a city.

Any suggestions or experiences with this stuff? I've done smaller bucket type container plants on the patio but I'm interested in this for aesthetics, food production, and just for the learning experience.

Maybe work on high tech ways to grow high value foods like sweet potatoes, soybeans and wheat indoors. Aeroponics with additional support structures maybe.

Are these techniques likely to be all that different from the techniques used to grow marijuana indoors? I was under the impression that a decent amount of R&D already went toward this.

There is a fair amount of R&D for indoor growing, but not much emphasis on those high-value foods, especially for the most advanced techniques like aeroponics. And marijuana growers don't have the same goals in terms of energy efficiency or cost-effectiveness.

> And marijuana growers don't have the same goals in terms of energy efficiency or cost-effectiveness.

Huh??

They may have additional goals, but they surely share the goals of energy efficiency (this would actually be a much higher priority for them than it would be for legal growers, as you can get caught based on your energy signature) and cost-effectiveness.

Jason here, CEO at Edenworks.

Sweet potatoes, soybeans, and wheat are very much the purview of traditional big ag. They're highly commoditized, which actually makes them not very valuable. Compare a pound of flour (not even wheat crop itself @ $0.50 retail) to a pound of salad greens ($10-15 retail) or a pound of basil ($15-45). The reason the latter products are so expensive is because they're delicate. They don't travel well, have high shrink rates, and can be premiumized due to freshness. On a unit basis, fresh and highly perishable foods are the high value food. They're also the most nutritious.

OK, sorry, the word "value" is the issue here.

https://www.washingtonpost.com/lifestyle/food/why-salad-is-s...

Salad greens are not very nutritious. They are good business though.

Its very very tough to do (impossible with current techniques), but local/little/vertical/urban/high tech ag needs to take on big ag in commoditized foods if we are going to increase food security and decrease water and energy usage.

Sweet potatoes, soybeans, and wheat are the type of staples that provide a good source of calories and nutrition.

Its sort of like Tesla saying they can only focus on luxury vehicles. At first that's true, but at some point the tech needs to break through to the larger market in order to make a big impact.

I don't expect you or any other high tech growers to take on that challenge though, because it is very difficult research and engineering and marketing and extremely hard (next to impossible) to make the numbers add up with so much commodity competition. But our current agricultural approach for commodities wastes water and land.

Until we get to that point its mainly just hipster wankery (like Tesla).

On the opposite end of success we have a rooftop greenhouse in Vancouver being sold on craigslist: http://www.cbc.ca/news/canada/british-columbia/craigslist-va... (http://vancouver.craigslist.ca/van/bfs/5133023654.html).

>There is an ongoing lawsuit between the City, EasyPark (managers of the parkade) and Clay Haeber (a former board member of Alterrus and the current owner of the farm) over a deal that would have seen the business taken over by Affinor, a Montreal-based medical marijuana firm.

Yep, definitely Vancouver.

Is this related to verticrop on kickstarter: https://www.kickstarter.com/projects/verticrop/verticroptm-t...

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