If you’ve been keeping up, you know I don’t claim to have a lot of answers. Sometimes I give suggestions, sometimes I express intentions and sometimes I just get hope it’s not too late. It’s not very often when I’m able to give a solid answer that has a real chance of making things better for a lot of people. Today is one of those days, so thank you for being here to share it with me. And today is even better, because this one answer helps resolves not just one question, but three. The questions will come shortly. But first, let me introduce you to the answer.

What is a hydroponic greenhouse?

Boy, am I glad you asked. One of the coolest things about plants (deception and diet notwithstanding) is the fact that they don’t actually need soil to grow. Despite what your ninth-grade biology teacher told you, plants only require three things: light, water, and nutrients. Notice how neither soil nor classical music are on that list. A hydroponic greenhouse takes full advantage of that fact, giving plants what they crave without all the unnecessary dirt. There are a few different ways it can do this. Here are the most popular.

Water culture

A water culture is probably the easiest to set up. You stick the plant into a growth medium (like perlite or coarse sand) and float it on top of a tank of water with an air pump at the bottom. Piece of cake, right? I dunno. Ask my daughter’s dead cabbage. Her father can’t grow squat.

Drip

I’m sure you can guess how this one gets the plants the water. It’s pumped to a little drip line and then falls down onto the plant, which is still in a growth medium. From there, you can choose to recover the water in a tank at the bottom, or not. For our purposes, let’s do the recovery part.

Nutrient Film Technique

This is one of my favorites. The plants’ roots just dangle free into the tray and a nutrient solution is pumped across them, keeping them fed and (probably) tickling a little in the process.

Aeroponics

Because hydroponics didn’t sound high-tech enough. An aeroponic system also gives the plants full freedom. Every few minutes, a fine nutrient mist is sprayed onto the roots. It’s basically the ante mortem equivalent of the vegetable mister at the supermarket. Those sound pretty fancy, right? But what advantages do they have over regular farms? We’ll talk more about that when we explore the three questions, starting with ….

How can we conserve more water?

Remember during water conservation week when we talked about the Ogallala Aquifer? To recap, it’s losing 32 ½ trillion gallons of water each year. Most of it goes to agriculture. Traditional agriculture has a pretty simple irrigation model. It goes like “put a bunch of water on the field and hope it sticks!” So, you end up with gigantic sprayers, crouching mantis-like over the field and shooting water out when the timer tells it to. Seems pretty inefficient, doesn’t it? Well, it is. This type of sprinkler irrigation has an efficiency rate of about 75 percent. It loses a full quarter of its water through evaporation or runoff before it can even get to the roots. Depending on the type of growth system you’re using, a hydroponic greenhouse can lose as little at 1 ½ percent of its water per day. This is where the recovery part comes in. After it’s passed over the plant’s roots, the water is recaptured, re-nutrient-ed and reapplied to the plant’s nether regions. Because of this recirculation, a hydroponic system requires significantly less water than a traditional setup. Most estimates put it at about 90 percent less. And since the United States uses about 80 percent of its water for agriculture, that amounts to some pretty significant savings.

How can we reduce the environmental impact of farming?

Agriculture, as it turns out, is the leading cause of river and lake pollution in the US. After the crops get sprayed with water like a hapless crowd in a mobster movie, the bullets that don’t hit a plant collect up all the nastiness on the ground and take it with them. Agricultural runoff carries soil, fertilizer, pesticides, salts and metals into the same freshwater sources we drink from. We’re literally sacrificing our drinking water in order to eat. And that’s not even considering the effects it has on the plants and animals that call the lakes home. When you dump fertilizer into a lake, it doesn’t stop being fertilizer. All of those nutrients are still just itching to do some fertilizing. And algae is just waiting to snap them up. Farm runoff has a nasty habit of causing algal blooms, which grow until they literally consume all the oxygen in the area, leaving none for the fish or other plants. Jerks. Y’know where the runoff goes from a hydroponic farm? If you guessed nowhere, give yourself a pat on the back because I’m too broke to send prizes. Putting the water directly on the plants’ roots and recirculating what isn’t used until it is means there’s no runoff (unless there’s a leak, which does happen, but on the scale of irrigation).

How can we feed more people?

Earth is crowded, if you haven’t noticed. People are just stinkin’ everywhere. And they all have one thing in common. They’re hungry. Between 2012 and 2014, 11 percent of the world’s population suffered from undernourishment. That’s 805 million people. Part of the problem is poverty, part of it is conflict, and part of it is hunger itself. Hungry people don’t work or think very well, which means they end up even hungrier when they don’t get paid. Most victims of hunger come from developing countries that are already water-stressed. They live in African or Asian nations where clean water is even scarcer than food. Without adequate clean water, crops grow poorly, if they grow at all. If only there were some sort of magical system that used less water. Then water-stressed people wouldn’t have to choose between drinking and growing. Crops could be grown basically anywhere. Speaking of which… Cropland makes up 11 percent of Earth’s surface. Another 68 percent is used for other stuff, like livestock and cities and junk. That leaves 21 percent of the surface of our rock basically sitting idle. We can’t grow crops there, because the soil is bad or it’s too cold or too hot or too dry or too whiny or some excuse that doesn’t matter because a greenhouse can work anywhere! Sure, it may take some heating if we’re gonna cover Antarctica with greenhouses staffed entirely by penguins. But it could be done. Plants would grow, people would be fed. And they’d be fed at a ridiculous rate. Because hydroponic greenhouses don’t have to worry about pesky things like seasons, they can produce year-round. Depending on the time it takes the plants to bear fruit, you could see three or four extra growth cycles. That is, if the plant ever stops producing. If that wasn’t enough extra food, why not go for almost three times more yield per acre? Because they don’t have to worry about dumb things like the ground, hydroponic farms can be planted vertically. Plants can grow in layers, each layer producing just about as much food as a traditional, single-story farm. So, let’s math that. Let’s say we only use the land we’re currently farming on, ignoring the 21 percent that’s unused, and the 9 percent that’s urban area (where we can grow on rooftops and in living rooms). On our 11 percent of land, we’ll go low and assume we can get three growth cycles average per year. That’s three times more food. But, if we stack three layers of plants and run those through three “seasons” we’re looking at nine times as much food just from the land we’re using now. I don’t know if you noticed, but I’m pretty excited about hydroponic farming. It may not be the absolute global solution to every problem, ever, but it sure does come close.