There are no seasons in an insulated freight container - so every FreightFarm is able to produce several hundred heads of lettuce or other leafy greens each week, year-round, no matter the location.

FreightFarms, the Boston-based brainchild of entrepreneurs Jon Friedman and Brad McNamara, started in 2010 by buying used refrigeration containers - also known as reefers - and turning them into ready-to-go hydroponic indoor farms.

"We tear all the refrigeration gear out of the reefers, but leave the insulation," said Caroline Katsiroubas, who joined the company as its first employee two and a half years ago. "Then we refurbish them and install the hydroponics equipment, climate controls and other parts of the system."

By the time FreightFarm is done setting up a complete hydroponic system in a refurbished reefer, it's priced at $82,000. That price includes a mandatory two-day training program in Boston, where newbies are shown how to manage the farm.

So far, Katsiroubis told DW, the company has sold 54 FreightFarms to urban-farmer clients like former teacher Connie Cooney and her husband Shawn, a baby-boomer couple in East Boston, who started Corner Stalk Farm in the city a couple of years ago and now operate five FreightFarms containers.

Seedlings await transplant to the vertical ZipFarm growing racks where they'll be grown out to harvestable size

While the setup is great for locally growing fresh vegetables, less clear is whether the high energy use ultimately makes this an eco-friendly option. If renewable energy could be brought into the mix, modular hydroponic systems like FreightFarms could become ubiquitous - if they could become affordable enough.

Environmental advantages

FreightFarms doesn't skimp on the tech - the package includes a smartphone app allowing them to monitor the temperature, humidity, CO2 and nutrient flow levels remotely, and to view the inside of the container by connecting to a built-in monitoring camera.

There's also the option of having seeds, nutrients, and growing medium delivered to their door, and even built-in speakers in the containers to enable music to smooth the day's work-flow. Each container entails about 15 to 20 hours of labor per week, according to Katsiroubas.

No doubt, FreightFarms containers work well in terms of producing green veggies. The system is set up so that not very much can go wrong: Given water and power hookups, if FreightFarmers get on with their work, they'll get their fresh greens.

On the positive side environmentally, FreightFarms use up-cycled refrigerated freight containers, or reefers, that have been dropped from the cargo fleet. Used 40-foot reefers in decent shape can be had for around $5,000 - about a quarter of the price of new ones.

Inspecting the seedlings prior to transplanting them into the ZipFarm growing racks

Moreover, if greens are produced locally year-round, most of the transport and refrigeration costs normally associated with providing fresh greens in groceries fall away. So there'd be no need to burn fossil fuels to move greens in refrigerated trucks from southern California or Mexico to the rest of the country during an American winter, for example.

Question of cost

In terms of costs, first there's the initial price of the system: $82,000, plus the cost of having a FreightFarm delivered to the client's location. Next, there's the cost of operating the farm: Electricity, fertilizers, seeds, water, boxes for transport to local customers, and other minor costs.

According to FreightFarms, the basic operating cost of a typical container under US conditions is currently about $13,000 a year, excluding labor, minor expenses, and any provision for renting the land on which the container sits.

FreightFarms are optimized to grow leafy greens like herbs (mint, basil, oregano), lettuces (bibb, romaine, arugula), brassicas (cabbage, mustard greens, Brussels sprouts, kale). The price obtained for the greens depends on who the customer is - for example, an urban farmer might target upscale restaurants that put a premium on freshness.

Greens growing out in the ZipFarm vertical growing racks, close to harvest size

"On a weekly basis, you can expect to harvest over 500 full-size heads of lettuce, or more than 1,000 heads of baby lettuce," the company says. But they won't specify revenue estimates, since production revenues vary from place to place and time to time, as well as according to crop choices.

The power question

Aside from labor, the biggest item on the list of operating costs is electricity: a single FreightFarm uses about 30,000 kWh of electricity a year. That's a lot - equivalent to the amount needed to power six or seven single-family homes in Germany per year.

Since in places like Germany, the retail price of electricity is quite a lot higher than in the US, buying power from the grid could quickly make the cost of operating a FreightFarm in Germany prohibitive - although that concern remains irrelevant for now, since the company only sells FreightFarms in the US and Canada so far.

And if that electricity were to be supplied by coal-fired power plants, that's certainly not an environmental win. But could a FreightFarm be powered by renewable electricity?

In ideal North German conditions, "It would take at least 150 square meters of high-efficiency solar photovoltaic panels to provide 30,000 kWh over the course of a year," said to Volker Quaschning, a renewable energy expert in Berlin.

FreightFarms says the percentage of container-grown greens that are marketable is about 93 percent, in contrast to 75 percent on field-grown greens

"The electricity consumption is so high that I'm skeptical this makes sense," Quaschning told DW.

One FreightFarm would take an area at least five times the size of its own footprint to be powered with solar panels. That might be feasible if the panels were set up on the roof of a grocery store, and the store's staff operated a container farm set up on the abundant land in its parking lot.

Then the fuel burned to transport the fresh greens to point-of-retail would drop away, again making a good environmental case.

Although the financial costs involved might not provide a compelling business case for FreightFarms around the world at this point in time, as the price of renewable energy continues to go down, fresh greens being grown in hydroponic container farms could yet become a routine part of the grocery business.

In Berlin, there's a variation on the same idea: An urban farm combining aquaponics, or fish farming in tanks, with hydroponic greenhouses for growing greens, tucked away on a lot behind a post office and hardware store. But unlike FreightFarms, Berlin-based "Ecofriendly Farmsystems" is not based on using freight containers, and the greenhouses are made of glass, so the plants grow primarily in natural light.