There are around 6,000 cargo vessels out on the ocean right now, carrying 20,000,000 shipping containers, which are delivering most of the products you see around you. And among all the containers are a special subset of temperature-controlled units known in the global cargo industry, in all seriousness, as reefers.

70% of what we eat passes through the global cold chain, a series of artificially-cooled spaces, which is where the reefer comes into play.

Dunedin, first clipper ship to complete a successful shipment of refrigerated meat byFrederick Tudgay

Prior to the rise of mass containerization, cooled goods on a bulk cargo ship were stored together in a single space. That zone could be kept at just one temperature, so it could only carry one product at a time.

When goods arrived in port, the local economy would be flooded with that single commodity, be it fresh produce or frozen meat. Prices dropped, food was wasted, and consumers got fed up with eating too much of one product at a time.

Containers in transit by SounderBruce, Roland Tanglao and Claudio

Containers in general, but especially the intermodal variety, were pioneered by trucker Malcolm McLean, and they changed the shipping game forever. Intermodal boxes were built to move by various forms of transit, able to be easily picked up from ships and dropped on trucks or trains without loading or unloading the contents. Goods moved faster and costs were reduced, as fewer workers were required throughout the process.

Unloading a container ship in Vancouver by Ruth Hartnup

For dry goods (those needing no refrigeration) the standard shipping container made transport easier right from its start. For goods needing temperature-controlled environments, the situation was more complex , as early refrigerated containers yielded mixed results.

No one knew why some shipments of perishable goods made it through to their destination port unscathed, while other shipments were partially or entirely rotted, or, conversely, frozen solid. Companies would pack tons of produce into refrigerated containers, send them on their way, and effectively hope for the best.

A refrigerated shipping container used to be like a scientific black box, where only inputs and outputs were observed.  Shipping companies made efforts to tweak temperatures and rearrange goods inside the container, but ports on the receiving end still opened containers full of frozen or spoiled fruits and vegetables. The reefers needed some additional analysis, and shipping companies needed some way to keep tabs on goods in transit.

Barbara Pratt, then and now, in mobile reefer lab and snow via Maersk

Thus, before it was cool to convert cargo containers into habitable architecture, some scientists created their own mobile laboratory inside a shipping container. This research lab had to be transported alongside cargo-filled containers as they made their way through the supply chain, from train to truck to ship. Installing the lab within a container was a natural choice.

One of these scientists, Barbara Pratt, is now the head of Reefer Services forMaersk, but in the 1970s she was a recent college graduate commissioned by General Foods to study container refrigeration. For seven years, she traveled with 40-foot converted steel box workspace that contained a giant computer, as well as a shower, microwave, bunk beds and, of course, a refrigerator.

The container lab connected to the other cargo containers on the ship with 150 sensors on the ends salt-resistant cables. These cables connected to the giant computer and monitored temperature, humidity levels, and gas concentrations of the goods in transit.

On ships, Pratt and her colleagues would stay in crew quarters, but they would cycle through the lab regularly, sometimes sleeping in their container alongside the computer.

As it turns out, a good reefer doesn’t just keep a consistent temperature– it also regulates airflow and controls internal atmosphere. The results of Pratt’s research impacted every aspect of shipping by reefer, from how goods are packed to how cool air is pumped into containers (from below rather than above).

The industry has continued to evolve in the decades since Pratt’s stint cruising the world on cargo vessels, and many innovations have grown out of her work. In today’s high-tech containers, the process of ripening fruit can now be slowed down or sped up, timed to coincide with the dates on which produce will hit the supermarket shelves. Even fragile goods (like fish and flowers) are regularly sent inside these precisely-controlled reefers.

Container ship in San Francisco Bay by Steven Straiton

There is no doubt that containers have revolutionized the way we ship and consume goods around the world. While locavores may lament the globalization of food and associated environmental implications, the global shipping industry, Pratt argues, encourages to eat more healthily. In many climates, fresh fruits and vegetables would not be available year-round without the artificial cryosphere: the vast global networks of refrigerated shipping and storage spaces. For better or for worse, reefers are an integral part of our modern existence.

Cargo container stacks by Russell Street, modified by Kurt Kohlstedt

Meanwhile, for some containers, shipping is still not quite the end of the story. The globally-standardized shipping module has inspired some fresh architectural applications, and reefers in particular are ideal candidates for adaptive reuse, as they are already insulated and designed around airflow.

Container house by m-louis

Steel containers, while robustly constructed, are inevitably damaged and even slightly defective units are generally removed from the supply chain. Containers also tend to pile up in places with more imports than exports, (aka the West) so it’s often easier for companies to offload old containers locally than to ship them back empty.

APAP OpenSchool by LOT-EK Architects

As a result, industrious individuals and professionals have converted surplus containers to homes, offices, schools, and more. In turn, ancillary industries have sprouted to support this movement, supplying standardized ways to connect containers with utilities and otherwise modify them for alternative uses.

Some architects have taken to specializing in containerized dwellings, offering container-specific prefab plans and design services. In their second lives on land, human-habitable containers still raise questions of temperature control; even now, there may be more to learn from Pratt’s time in a shipping container at sea.

Freitag retail store in Zurich by Alicia Bramlett

For this story, Nicola Twilley, reporter and founder of Edible Geography and co-host of Gastropod, spoke with Barbara Pratt, Director of Refrigerated Services at Maersk. Learn more about containers near you in The Container Guide by Craig Cannon and Tim Hwang. Lead image by Håkan Dahlström.