The biggest competitor to the ISO tank container is the flexitank, which is essentially a large plastic bag that goes inside a standard 20-foot dry box.
Wine shippers, in particular, have gravitated to flexitanks in recent years as their choice for transporting bulk shipments to overseas markets for bottling.
'Some wineries have the perception that stainless steel tank containers protect wine better, but that's not really true,' said Bob Bruns, president of Lodi, Calif.-based JIB International, which specializes in the transportation of wines. 'Flexitanks protect it just as well.'
Flexitanks can hold up to 24,000 liters of wine per load. 'We request that the ocean carriers stow these containers below deck for a more constant temperature in transit,' Bruns said.
The best part about the flexitanks, proponents say, is that there's no cleaning required after discharging the product. 'You simply dispose of the bags when you're done,' Bruns said.
Several years ago attempts were made by some flexitank manufacturers and users to clean the bags for reuse. Many shippers rebelled against the concept. 'The winemakers went nuts. They worried about tainting their wine loads,' Bruns said.
However, like the ISO tank containers, flexitanks also have their logistics challenges. For instance, railroads will not accept containerized flexitanks due to concerns that the bags of wine may rupture and leak in transit due to the motion of the trains. Truck is still the only way to efficiently move these containers from the wineries to the ports for vessel loading.
The American Association of Railroads and the wine industry continue to explore ways to remedy the problem with flexitanks so these containerized shipments can also take advantage of the country's mini-landbridge services.
Another problem with flexitanks is that they're limited to non-hazardous liquid commodities. For example, shippers of spirits cannot use them due to the high alcohol content.