Vertical Farming: The Good, the Bad and the Ugly

By now, the images of shelves full of perfect greens in hulking warehouses, stacked floor to ceiling in sterile environments and illuminated by high-powered LED lights, have become familiar. Food futurists and industry leaders say these high-tech vertical farming operations are the future of agriculture — able to operate anywhere, virtually invincible against pests, pathogens, and poor weather, and producing local, fresh, high-quality, lower-carbon food year-round.

But it’s time we start asking questions. And the first question that comes to our minds is why we need to shift our base from cropland to rooftops?

THE GOOD

Locally Grown Food

As the farm-to-table movement takes hold globally, a technology-enabled revolution is brewing that could fundamentally change the way we source fresh produce.

Out of tiny shipping containers, on rooftops or in converted steel mills, these climate-controlled farms are producing everything from micro greens and leafy lettuces to mushrooms and tomatoes.

The produce can be delivered to restaurants and locality just hours after harvest and year round. There are no variables for weather or global warming; no need for pesticides or herbicides. In fact, in some cases, there’s no soil involved.

This also means no transportation cost or carbon emission.

Space Optimization

You know the story till now; but in case, here’s in a nutshell; less land to grow food; more mouths to feed. Big problem!

But, increasingly, forward-thinking farmers are eschewing the confines of agriculture and growing on what’s traditionally been considered unused space; city rooftops. With decreasing use of cropland, and stacking our crops on vertical layers, the productivity of a farmed surface is increased by a factor of four to six. Vertical farming quite literally, suggests that the sky’s the limit for growing crops. While it’s for further study whether Vertical Farming can be adopted for all kind of crops, but as of now we know that there are crops that are quiet effectively grown in it. So from this we can infer that it will ultimately optimize the space for crops that are grown traditionally.

“The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human being.” This saying by Masanobu Fukuoka has always been one of the most important but neglected aspects of farming.

Adds Up to the Social Relations

Farming is about the hard work we sow, the care we show and the friendships that we cultivate. There is no greater bond than bonding over food. Along with beatifying human relationships it beautifies our city. This fresh gush of wind purifies the ever polluted cities with its calming presence. It also puts to use our abandoned buildings to give them a purpose as well. Though the amount of food produced by vertical farming requires study it sure does produce a lot of valuable social relationships.

So far so good. Then why are crops still grown on open farms?

THE BAD

The Unnecessary Hype

Before we dive into vertical farming, let’s take a pause and spare some thought. Remember what we learnt about farming in our childhood days? Farming back then was a simple affair, simple but efficient. Our ancestors used whatever was naturally accessible; the water down the sky, animals that could plough the land and produced the food. Now if we fast forward to modern day agriculture, we are digging up the soil for ground water, burning fossil fuels to run machineries and chemicals to double up the yields. Our agriculture changed to survive.

But the question arises whether this survival can sustain? This survival will actually lead us to extinction. So we came up with a solution. A solution where we can produce our foods locally almost without water and even without soil. And we thought we have made everything all right. But have we really?

Vertical Farming has been hyped as if it’s the answer to all our problems, when the vertical farms have a lot of questions about itself being unanswered.

Carbon Footprint

As we move further let us ask ourselves what is the most important point that we have been missing? While getting excited about less water no soil and vertically stalked farms in indoors, we may have completely ignored the most important factor in the yield of a field; the energy that goes in into the farms; the sunlight. The yield is studied to be 2 to 5% of the energy that goes into the farming. And that sunlight is not available in this farming.

Study suggests an average passenger car in US emits 5100 kg of CO2 per year, also in vertical farming nearly 8 kg of CO2 is released per kg of lettuce. So if we divide 5100 by 8 its 636 kg of lettuce; 636 kg of lettuce is equal to 4000 heads of lettuce, which is in turn generally a 3 day production of a vertical farm. Yes that’s right 3 days production is all it takes to produce carbon emission equal to that of a car in an entire year.

There can be a point of confusion that why can’t we use solar panels and photovoltaic cells to power the artificial lights. Well this is a good alternative measure proposed. But since you’ve read through this we can assume you understand that we can’t put solar panels on each layer of the vertical stacks they can only be on the top layer. And trust us when we say that’s simply not enough.

Take two different scenarios a greenhouse farm with open access to sunlight and a vertical farm lit by best in market LEDs powered by the most efficient solar voltaics. Now visible light at solar noon is about 2000 micro-moles/m^2. This drives photosynthesis and plant growth. On the other hand total solar radiation is 1000 W/m^2 which drives solar voltaics. Both are the same energy with different units. When greenhouse takes up 70% transmission, the solar voltaics are only 15% efficient, and the LEDs can produce 1.74 micro moles/joule. Plain mathematics is all it takes to understand 5.4 acres of solar panels are required to produce 1 acre of sunlight equivalent.

Not for Everyone

In 1970 on the world’s first Earth Day, leading ecologist, Dr. Barry Commoner laid out four basic rules for human’s relationship to the environment. One of them was “There is no such thing as a free lunch”. Simple Google search reveals such incredible conceptual drawings and some wonderous advantages of vertical farming. But where do its

Let’s talk about bread.

New York City residents each consumed about 24kg of bread per year. It would take about 8.6m square metres of floor space stacked three high per floor, to grow New York City’s wheat. That’s equal to nearly three Empire State Buildings. It might seem very efficient to produce all the bread in three large buildings, but constructing and running them will have their own environmental footprint.

Assuming the use of efficient red-blue LEDs at $0.10 per kilowatt-hour, production alone would cost about $327 per square metre per year. If turned into bread it would cost $11 per loaf of bread to cover the lighting cost.

The elite market is being targeted here who are both capable and willing to indulge in a bread loaf for $11.

Another aspect that we have been ignoring since the inception of the hype of this kind of farming is that; this is going to take a lot more than being just a farmer to grow crops in vertical stalks, it requires architects, and engineers, and biologists. So a lot of farmers are going to lose their jobs, which is absolutely not something we are aiming at.

THE UGLY

Not the Answer to Global Food Security

Global food security is one of the main threats we face in today’s world. Genuine food security means that when the ice road is closed, or the airplane can’t fly, the community can still feed itself the staple foods needed for survival and basic health. The vast majority of these systems produce only vegetables, and especially low-calorie vegetables like lettuce, kale, chard, spinach, herbs, etc. because most of those plants’ weight can be sold and eaten. Human beings cannot survive on these types of foods. If potatoes, tomatoes or green beans were being grown, much precious building space and costly electricity would go into producing inedible leaves, stems and roots. So if you think vertical farming will provide us with food security then think again or may be start taking basil for breakfast, lettuce for lunch and spinach for dinner.

Non Caloric Food

We said earlier that growing plants with higher dry weight is not really feasible in indoor farming. To get a better idea let’s analyze some numbers.

Let’s think of photons and food; how much photons it takes to make food. Well we have a really simple calculation to understand the stuff.

1 mole of photon gives out 1gm of biomass. And 1gm of biomass is equivalent to 1/2gm of yield. Now the analysis:

• First we have the absorption of 1 mole of photons during photosynthesis by leaves, let’s take an optimistic value, say 90%.
• Then we have the quantum yield, this is nothing but the moles of carbon fixed/mole of photons absorbed; studies suggest the ratio can be as high as 0.07.
• Now the conversion efficiency in respiration is 65%. Keeping account of the fact that plants exhale CO2 at night.
• Next we have the harvest index; for those who don’t know what that is, it is basically the ratio of harvesting crop to the total shoot dry matter. It is 85% for lettuce.

Therefore, by sequential multiplication we have 0.035 moles of carbon/moles of photons. Transferring moles of carbon into dry weight, we have about 42% of carbon in lettuce. Now we have 12gm of lettuce/mole of carbon. So, we have 1gm of dry weight of lettuce/mole of carbon.

On the next level we have the electricity charges, in US it is 10 cents/KWH. With best efficiencies of LEDs in market, we have:

$32for electricity/kg of dry weight.

It was alright if it would have been for a plant with 95% of water. But what about crops like wheat. What is its worth $3 to $4? Okay for the sake of local producers let’s say a $9. Well electricity for wheat will cost 32 cents/kg of dry weight. That’s 100 times of the actual cost of wheat.

What we mean here is this is not a sci-fi movie like The Martian, where an astronaut is growing potatoes on such a sparse lighting set up on any planet. It is about time we get to know the reality, plants like potato or tomato that produce a fleshy food product require about 1,200 kilowatt-hours of electricity for each kilogram of edible tissue they produce, not counting the water stored in the food. That requirement approximates the annual electricity consumption of the average American home refrigerator; and that’s a big energy bill to produce just two and a quarter pounds of food dry matter. At that rate, producing America’s annual vegetable crop (not counting potatoes) in vertical systems under lights would require well over half of the electricity this country generates every year.

The Economy does not Add Up

There is an interesting circular logic in vertical farming: that we would use solar arrays and wind farms to convert sunlight’s energy into electric current that would feed lamps that would convert a portion of the electrical energy into artificial sunlight to shine on plants so they can convert that light energy into food. Yes the economic system of vertical farming is such a spiral hub. Leave the energy loss at each junction think about the cost at each level of such a system.

In addition to the hefty electricity bills due to lights we have a few other factors that require attention as well. One of the most striking features of vertical farming is the abnormally less use of water in farming. When we say traditional farming takes up about 70% of Earth’s water, we are like oh my god! We must be wasting it terribly; we won’t have water left to drink.

But it’s far from reality, it is true crops specially the high value ones take in a lot of water, but it’s what they require to give a proper yield which is restored in environment enough through transpiration. But to stop this wastage of water indoor farms use dehumidifier, that dehumidifies the water from the air, condenses it and puts it back into the roots. Great! But what about the latent heat of condensation of water which is enormous and the electricity it takes is 14 bucks/cubic liter.

Then there are things like coolers, refrigerators. By claiming to be “revolutionary,” vertical-gardening advocates are seeking to be viewed as part of such a transformation. But thanks to their hefty electric bills and limited crop range, they will have a hard time venturing beyond the elite market, let alone reducing their climate impact.

Urban agriculture is the future, the people’s interest in growing their own food and being connected to it is admirable. But it is not supposed to be under artificial lights, we must find a way to optimize the use of sunlight. Every photon is precious, let’s seize it and grow food. Don’t live under the impression that buying electricity to grow crops is going to save the world. Vertical farming though can be excellent supplemental solution. We now need a broad-based political, economic and ecological uprising — and that will neither start nor finish in high-rise vegetable factories. We at FarmatroniX believe in preserving the essence of farming while amalgamating it with new age technology. Come and join us, may be together we can make things happen.