It’s a Weird Time to be Alive

It is certainly unprecedented in human history to have anytime, on-demand access to almost any type of food, prepared in any way imaginable. Yet, as residents of the developed world in the 21^st century, we find ourselves in this strange situation. Most of us are not exceedingly wealthy by American standards but are among the wealthiest of the wealthiest humans that have ever lived. Each day you and I have the option to dine on some of the best-tasting foods ever made. Let’s take a minute to reflect on the fact that on any given day any of us can taste something that is objectively more delicious that anything Alexander the Great tasted in his lifetime. We also have access to any kind of food, any time. For instance, my kids ate watermelon for dessert last night. In February. We all know watermelon is a summer treat. It’s a weird time to be alive, indeed.

The Costs of Privilege

Of course, this unmatched privilege comes with costs, as do all good things. Tremendous advancements in agriculture over the past two centuries have allowed for unprecedented human flourishing, but have also contributed, in part, to climate change which threatens to alter our environment for years to come. But, as we look for potential solutions, it would probably be a good idea to glance back from time to time to learn from our predecessors.

I often think about a picture I’ve looked at many times of my childhood home. The house was built in 1929 on an experimental farm in south Alabama. The actual focus of the picture I’m referring to is a couple of farm workers alongside their trusty mule, but the house I grew up in can be seen a few hundred yards in the background, standing alone, surrounded by hundreds of acres of farmland. The key word in the previous sentence is “alone”. Every tree in view of the camera had been cut down. This was common in the early 20^th century, and before. We can look back with 21^st century glasses and scoff at this practice, but it would be foolish to do so without at least considering the mindset of the farmers in the picture. Did they know all the consequences of clear-cutting the land? Certainly not. Did they believe they had done the right thing by “freeing up” all that good land for crops? Probably so. Fast forward nearly 100 years and we can clearly see that those farmers did not know the best way to steward the land. There is a common phrase about hindsight that comes to mind here. I bring up this anecdote not primarily as an example of how ignorant or backwards our great-great-great-grandparents were, but as how ignorant we may one day look to our great-great-great-grandchildren. Those farmers in that picture didn’t know what they didn’t know and neither do we. So, with that in mind, let’s humbly look at our current and future situation.

Bad News and Good News?

Agricultural production is a major source of greenhouse gas emissions. When looking at the linked graphic, one can easily see that “food type” is the most important factor determining the environmental impact of agriculture. We can also clearly see that, for the most part, plant-based production systems account for far lower emissions than do other types of systems, the most notable exceptions being chocolate, coffee, and various oils of plant origin. Overall, grain and vegetable production systems account for a small percentage of ag-based global emissions. This is good news! Let me explain.

First off, plant-based diets are often cited in the literature as healthful for humans. To be sure, animal meats and fats can also be good for you when enjoyed in moderation. As Michael Pollan, author of many books including “The Omnivore’s Dilemma” and “In Defense of Food: An Eater’s Manifesto,” eloquently and succinctly puts it “Eat food. Not too much. Mostly plants.”  Secondly, most diets across the globe are, in fact, plant based. I often pose the question “how do we feed the world?” to my students at the beginning of each semester. When I ask the question, I’m not looking to learn the mechanisms of farming practices. I am trying to discern whether my students really know where human sustenance comes from. Where do most humans derive their life-sustaining calories? The most correct answer is “grains.” Wheat, rice, and corn to be more direct. There are many reasons for this, but we can summarize them by pointing out that grains are nutritional “powerhouses” in dryable, shippable form. Nearly the perfect energy source. The students in my classes are often surprised by this question and answer combo, because I teach classes focused on vegetable production. In particular, my “HORT 2060: Hydroponics” class covers production of vegetables in small-footprint, enclosed, environmentally controlled structures like greenhouses and vertical farms (more on that later). Grains are row crops produced on vast tracts of land, much of which is in the Midwestern U.S., and exported all over the world. As we have already seen, grains are still only accountable for a small portion of ag-related greenhouse gas emissions. Vegetables are an even smaller contributor then to climate change. So, what’s the point? The point is that although vegetable production contributes only a small proportion of greenhouse gas emissions from agriculture, not all vegetable production is created equal.

Veggies of the Past and Present

For centuries, vegetable production has been practiced in a similar fashion to row crop (grains, et al.) production. Soil-based vegetable farming was and is the source of most of the world’s vegetables. Most of the vegetables traded globally and domestically are field-grown and although vegetable production is possible almost anywhere, certain locations have become major production centers due mainly to their ideal climates. Supportive infrastructures have followed, and incredibly large, centralized markets have developed. For example, in terms of value,  nearly 60% of the vegetable crop in the United States in 2017 was produced in California. However, weather patterns are changing and the vegetable production sector is evolving both domestically and globally.

Controlled Environment Agriculture (CEA), which can be defined as “plant production in (semi)controlled environments such as greenhouses, which use natural light and/or supplementary artificial light, or fully-enclosed environments such as warehouses and shipping containers, which allow for full control of environmental conditions but rely solely on artificial light” has made more localized vegetable production possible throughout the developed world because it helps negate some climate-related production issues like hard freezes and low light. Greenhouses have been used to produce fresh vegetables for decades, especially in northern climates. The most advanced greenhouses in the world originated and have continued to develop in the Netherlands (Holland) and have made their way to North America. Dutch growers exported their technology to North America in the 20^th century to Canada first, then the U.S.

The benefits of greenhouses for vegetable production are numerous. A few examples are as follows: greenhouses are essentially solar collectors that maximize light, and CO₂ in some cases, the two primary drivers of plant growth and yield. In addition, plant-essential nutrients (N, P, K, etc.) can be delivered directly to plant roots via drip irrigation or similar technologies, using complex, computer controlled, re-circulating systems which allow for extremely high water- and nutrient-use efficiencies and savings. Finally, greenhouses can be located in places where traditional agriculture is impossible, including urban, peri-urban, or suburban areas. This significantly shortens the supply chains for fresh vegetables. Maybe more importantly greenhouse technology increases the quality of produce. As an example, tomatoes that are commonly available in American grocery stores or restaurants are usually picked “mature green”, shipped from their place of origin (mostly likely California or Mexico, but sometimes Florida), and ripened in large storage bins or shipping containers with ethylene. While there is nothing dangerous about this at all, the fact remains that tomatoes that are treated in this way simply do not taste as good as their vine-ripened counterparts. Growing tomatoes in greenhouses, closer to their destination, allows them to ripen on the plant, vastly improving their flavor profile. If you think you don’t like the taste of fresh tomatoes, I highly encourage you to try some greenhouse-grown snacking tomatoes available at any large retail grocery store. You just might discover why Thomas Jefferson affectionally called tomatoes “love apples.”

The factors that make greenhouses so great for plant production also cause some drawbacks. For example, greenhouses are covered with highly transmissive materials, usually either glass or plastic to maximize light transmission. The high amount of sunlight transmitted through these materials promotes plant growth by collecting solar energy which is either utilized by plants for photosynthesis or converted into heat energy which is naturally trapped inside the greenhouse (hence the term “greenhouse effect”). This is an excellent scenario for producing warm-season vegetables in the cool season, but much of the heat energy trapped inside the greenhouse must be released when temperatures rise above what is optimal for plants. Heat energy is often so high in greenhouses that solar radiation must be reduced via shading, which in turn reduces yields unless supplementary light is provided. Another drawback to greenhouses is that transmissive coverings have very low insulation values, so additional heat energy is often required to keep temperatures inside the greenhouse high enough for warm-season plants when it is cold outside. Heat must then be produced, usually by burning fossil fuels. Low photosynthetic activity during short days of the cool season must also be overcome by using high-energy supplemental light. As a result, it is often impossible to absolutely maximize plant yields in greenhouses without purchasing significant amounts of energy for light, heating, or cooling.

Veggies of the Future?

Vertical farming is the newest technology on the scene, which is promising to revolutionize food production as we know it. But can it deliver on its promises? There are numerous advantages of vertical farming that can be found at the attached link. Probably the most drastic “advantage” of vertical farms can best be visualized in Figure 1. Vertical farms essentially allow for tremendous gains in production per area, and in energy, water, and nutrient-use efficiencies. They also drastically reduce supply chain length, thereby potentially reducing food waste considerably.

Figure 1: Photo credit: https://www.eitfood.eu/blog/post/is-vertical-farming-really-sustainable

This sounds really good right? But it’s not the whole story. Not even close. The visualized data in Figure 1 are for lettuce production. Americans eat a lot of lettuce. But as we now hopefully realize, lettuce does not feed the world. Lettuce also represents a tiny fraction of the global greenhouse gas emissions from food crops. So, why not grow other crops in vertical farms? Because the physics simply do not work well. For vertical farms to provide such crazy high yields, plants must be stacked “vertically” several levels high. Lettuces and other food crops of similar stature make the most sense. Plus, lettuce is relatively valuable which is a must because even though vertical farms are incredibly efficient, all their energy must currently be purchased.

What’s wrong with purchased energy? Well, as a reminder, there just so happens to be a gigantic flaming ball of gas nearby which “produces the equivalent of 38,460 septillion watts (3.846×1026 W) per second. To put that in perspective, this is the equivalent of about 9.192×1010 megatons of TNT per second, or 1,820,000,000 Tsar Bombas – the most powerful thermonuclear bomb ever built!” Seems like a lot. In vertical farms we have decided to shun the sun, as it were, in order to completely control the growing environment of the plant. We use highly efficient LEDs to provide all the light the plant needs and HVAC systems to keep temperature and humidity dialed in. Okay, but no matter how efficient LEDs become, they will never be as efficient as THE SUN^TM.  This is all of course very tongue-in-cheek and maybe a bit too sarcastic, but I think I’ve made the point that vertical farming may have a role to play in food production moving forward, but its role will be limited unless we figure out how to do cold fusion (Here’s looking at you Senator Warren…).

In all seriousness though, there are a tremendous number of new and possible technologies that will greatly improve CEA sustainability. A few of my personal favorites, in no particular order, are large-scale geothermal energy, solar-powered greenhouses, and new co-generation projects.

The Survey Says…?

So, what’s the verdict? Are controlled environments the future of food production? I certainly believe they have a role to play, but I think we should understand that “food production” is a big issue. We need grains. We need meat, but maybe not as much as we currently have… We need field-produced vegetables to keep prices low. We certainly want people to be able to afford vegetables for a healthful diet. We need greenhouses to shorten supply chains and to provide us with incredibly high-quality, tasty vegetables with longer shelf lives. This will reduce food waste which is a huge problem we barely covered in this post. We will probably need vertical farms in some cases as well. I say all this knowing full well that we might be one or two technological advances away from solving all our problems, but that’s not very likely. Remember, we probably don’t know as much as we think we do. As we continue to make progress let’s be humble in our approach to food production, so that our great-great-great grandchildren won’t be too embarrassed when look at pictures of us standing in front of our shiny, new vertical farm.

Post contributed by Assistant Professor of Horticulture Daniel E. Wells