Countries that import refrigerated cargo like food or flowers often do not export the same amount of refrigerated cargo out of the country.
However, refrigerated containers still have to get back to where they're needed so they can start their use cycle again. For carriers, the cost of re-positioning an empty, unused container is significant. The last thing carriers want to do is load their ships with empty reefer containers because they're not generating revenue.
To incentivize the use of these containers, the carriers offer a discount to shippers for the use non-operating reefer (NOR) containers to transport dry goods. With the refrigeration off, reefer containers can be used like regular containers, with a few limitations.
Reefer containers are slightly smaller inside than regular containers because of the refrigeration equipment, and are also more susceptible to damage. Because of this, certain types of cargo can't be transported in NOR containers. Things like garments, toys, furniture, and paper materials are all safe to transport.
So if you have cargo that can be safely transported in a NOR container, you can save money on your next shipment. The repositioning generates revenue for the carriers, the containers get back to where they need to be to start their cycle again, and exporters have the opportunity to ship cargo at a discounted rate. It's a win-win for everyone.