The number of nitrogen (N2) filled containers sailing across the Pacific Ocean has increased recently, with the sustainability of fresh fruit and vegetables during shipping processes becoming a hot topic in Japan.

Shipping services using controlled atmosphere (CA) containers, which are filled with N2, are becoming more popular in the North Pacific rim country, according to the National Federation of Agricultural Cooperative Associations (JA ZEN-NOH), developing into a rapid, widespread adoption.

Encouraging increased usage of CA containers forms part of the Japanese Government’s Trans-Pacific Strategic Economic Partnership (TPP), which aims to export ¥1 trillion ($9.38bn) of agricultural, forestry and fishery products in the near future.

CA prevents the deterioration of fruit and vegetables when they are harvested for transport and the N2 atmosphere as the CA containers are optimised for quality control standards. Previous methods of refrigeration techniques were used before the introduction of CA, but the re-emergence of this method is fast becoming the preferred method of shipping in Japan.

Food, peppers, apples, vegetables

In Aomori and Nagano, which are famous apple producing regions, apples are currently being stored in warehouses which are using N2 pressure swing adsorption (PSA) generators to maintain optimum levels of 90% N2, 5% oxygen (O2) and 5% carbon dioxide (CO2) in the atmosphere.

Nippon Yusen Kaisha Line (NYK Line), the largest maritime transport company in Japan, is advocating the use of CA storage in marine transportation. Last year, NYK Line invested in 5,500 40ft containers – 700 of which were CA. The company has also begun to develop 20ft containers in order to easily handle smaller exports.

Kenji Tamura, Director and General Manager of the Marketing Group at the Monohakobi Technology Institute (MTI), who is responsible for developing shipping technology, noted, “With the improvement in CA container technology, not only can quality be maintained, but the cost of transportation by ship could be reduced to a tenth of the cost of transportation by air.”

“There is a large, underlying need to shift air transportation over to sea transportation, so it is predicted that CA container transport will increase.”

Tamura explained the three different types of CA containers; passive, active and maxtend. N2 is used in the active and maxtend types.

Last year, we recorded sales of a few containers for use mainly in trial transportation but we have high hopes and anticipate that an increase will happen in transportation from Japan to Asia

During the shipping process, fruit and vegetables ‘breath’ as they continuously release CO2 once harvested. Passive CA containers use inbuilt O2 and CO2 sensors along with modules to intake fresh air, so that when the CO2 density rises, the containers automatically intake fresh air to maintain preservation levels inside the vessels.

Active CA containers, which are the most popular, utilise an inbuilt N2 generator and are typically used as additional facilities to the passive containers. By actively inserting N2, O2 and CO2 levels are lowered which suppresses the ‘breathing’ of fruit and vegetables. This repository also allows for extended transportation by automatically controlling the storage area’s atmosphere levels using sensors combined with a constant, recurrent supply of N2.

The Maxtend method inserts N2 in advance into a reefer container after raising the air-tightness and decreasing the concentration of O2. The device utilises a polyvinyl chloride curtain to make it airtight before N2 is administered. Then by using the O2 and CO2 sensors at its air circulation window and control facility, the interior of the container is turned into a CA environment. For a 40ft container, approximately 50m3 of N2 is needed.

This type of container was developed by Mitsubishi Australia, with its N2 supplied by cylinders. It is understood that Mitsubishi Australia developed these containers at the request of the Australian government because CA containers were in short supply around the world in 2000.

NYK Line owns around 1,000 CA containers, divided into a 50/50 split between active and passive varieties, which are used to import bananas and avocados.

Daikin Industries manufactures both containers and PSA N2 generators, which use zeolite as its adsorption agent, in Japan. The company has also cultivated its PSA technology to be used in O2 concentrators for home O2 therapy (HOT).

Daikin has developed a PSA unit that uses a vacuum regeneration method which intakes N2 with the zeolite. It generates N2 with a purity of 95% and produces 10 litres per minute and is generally equipped as standard in active CA containers.

Additionally, Daikin holds around 20% of the total reefer container market – second to only US firm, Carrier. The corporation is widely regarded as having put CA containers on the map, after being adopted by NYK Line in Japan.

A spokesperson from the Cryogenic Division of Daikin Industries commented, “Right now, the only active type of CA containers at this level of practical use are ours. We are aiming to sell 1,000 containers this year.”

Future developments

With regards to the Maxtend variety, Japanese company, Yusen Logistics has entered into an agency agreement with Mitsubishi Australia to develop a CA container business. For this service in Japan, Air Water, along with other local gas distributors, will supply the N2 using cylinders with a filling pressure of 2.75MPa.

A spokesperson from the Business Development and SCM Solution Department of Yusen Logistics stated, “Right now, we are engaged in supplying Maxtend services in five ports; Yokohama, Shimizu, Nagoya, Kobe and Hakata. Last year, we recorded sales of a few containers for use mainly in trial transportation but we have high hopes and anticipate that an increase will happen in transportation from Japan to Asia.”

Fellow Japanese corporation, Kuraray Chemical, is currently developing a circulation type N2 PSA for use with CA storage. From November 2015 to February 2016, Kuraray delivered roughly 20 of these units, which have a capacity of under 10m3 an hour to be used with smaller CA storage.

The Gas Review explained that there was a stable demand from shipping companies in Central and South America that want to switch to using CA containers. The publication concluded, “Old and new CA storage technology will most certainly be thrust back into the limelight.”