On a recent walk one afternoon in Manhattan, I stumbled upon a shipping container. Parked on a small patch of concrete next to a subway exit in Soho, the steel box took up about the same amount of space as several parked cars. It was noticeable for its novelty but otherwise unobtrusive. I peered inside and saw electric pink lights and column after column of leafy greens.

The shipping container, it turns out, contained a hydroponic farming system capable of producing between two to four tons of produce each year. I turned the corner to the other side of the container and was promptly handed a bag of dinosaur kale, plucked just the day before from inside that very shipping container.

This particular container was created by a company called Freight Farms. According to its website, the box, called a Leafy Green Machine, "is capable of growing lettuces, herbs, and hearty greens at commercial scale in any climate or location." Produce can be grown year-round, using less than five gallons of water a day.

The farms are hydroponic systems, which means the plants are grown in liquid nutrients rather than in soil. The low water usage of the containers is partially due to the fact that leftover water gets recirculated. The neon pink lighting I noticed were the LED lamps that provide the plants with the right amount of light and can even affect how the plant looks and tastes. The light tends to appear pink or purple because chlorophyll, the pigment in plants that soaks up energy from light, absorbs red and blue light.

While the concept of shipping container farms was novel to me, they aren't new — and Freight Farms is far from the only company selling these farms-in-a-box to hopeful growers. Local Roots, Modular Farms, and Growtainer are just a few of the other major players in the space. Though these farms seem a natural fit for urban environments that are short on space, they aren't just cropping up in New York City. One farmer purchased a shipping container farm for her plot of land in Montana — a place with significantly more space than downtown Manhattan — because she says it allows her to grow fresh food year-round despite Montana's cold winters. Shipping containers are also getting parked in the Arctic, allowing people to grow fresh produce in the frigid climate and avoid the high costs and long waits associated with shipments from far-away farms. Furthermore, the food they are getting is more nutrient dense, as food can lose up to 45 percent of its nutritional value during transport.

Recently, NASA awarded a grant to Freight Farms and Clemson University to look into the possibility of growing food in space. Freight Farms says the innovations "could also be applied to other industries in need of a stable food supply, such as disaster relief, military bases, mining, and offshore industries." The Washington Post's Maura Judkis pointed out that "the flexibility and scalability of the farms has huge implications for food desserts" as well.

While these farms boast compactness, transportability, ready availability, and sustainability, there are challenges associated with them. Though shipping container farms seemingly make it easy for novice farmers to become green thumbs, these farms aren't an inexpensive investment — and it isn't always paying off, Vox reported recently:

Farming well requires deep know-how and expertise; it has proven extraordinarily difficult to expand vertical farms in a way that holds quality consistent while driving costs down. Optimizing production at a small scale is very different from doing so at a large scale. The landscape is littered with the corpses of vertical-farming startups that thought they could beat the odds (though several are still alive and kicking). [Vox]

Another issue is that not all fruits and veggies can be easily grown in a shipping container system. "Hydroponics and controlled-environment agriculture lends itself to certain types of produce, like highly perishable leafy greens, salads, herbs, and vining crops like tomatoes, cucumbers, and peppers," Viraj Puri, CEO of Brooklyn-based urban farming company Gotham Greens, told The Wall Street Journal. "But a lot of other ag staples can't be grown in a commercially profitable way, like grains, root vegetables, and tropical fruit." Puri predicts that these shipping container farms would be more of a complement to traditional farms rather than a replacement.

But even still, with a projected 2.4 billion more mouths to feed by 2050, an alternative source of fresh produce is certainly a mouthwatering prospect.