Container lines are tapping a longer alternative route for the backhaul leg of their Asia-US east coast and Asia-north Europe services on the back of lower fuel prices, cutting costs by avoiding charges they have to pay if they sail through either the Panama or Suez Canal, Copenhagen-based SeaIntel Maritime Analysis said.
Despite the longer distance, the move is economically viable due to the drop in bunker fuel prices, the research group said. Carriers are able to speed up on the backhaul journey and keep the number of vessels and the round-trip length unchanged.
“In what seems to be a major deployment change largely unnoticed by industry followers, carriers have started re-routing the backhaul legs of most Asia to  US east coast services around the south of Africa, as opposed to the traditional routing through either the Panama or Suez canals,” SeaIntel said.
"While a major blow to the two canals, the economics behind this model is quite sound," SeaIntel added.
Among the Asia-North Europe services, the NE5 and NC6 operated by the CKYHE alliance and the FAL8/AEX1/AEC1 operated by the Ocean Three alliance recently used the south of Africa route on the backhaul leg, according to SeaIntel. 
Since the end of October 2015, 115 vessels deployed on Asia-USEC and Asia-north Europe services made the trip back to Asia by sailing south of Africa rather than through the Suez and Panama canals, which they sailed through on the headhaul leg, SeaIntel said.
SeaIntel said that the drop in the number of containerships transiting the Suez Canal in 2015 can be partially attributed to carriers sailing south of Africa on the backhaul.
The number of laden container vessels passing through the Suez Canal in 2015 dropped 2.8% from the previous year to 5,894, based on data posted on the Suez Canal Authority website.
SeaIntel identified 14 USEC-Asia services that could potentially save money by using the south of Africa route while keeping the same transit time and rotation of the original service. Of the 14, eight currently sail through the Panama Canal and six through the Suez Canal on the headhaul.
Of the six USEC-Asia services sailing through the Suez Canal on the headhaul, using the south of Africa route on the backhaul can mean savings on average of about $380,000 per voyage. The savings assumed the bunker fuel price of $150/tonne, an additional 1,500nm sailing distance on average and a faster speed of 15.7 knots on average using the south of Africa route instead of the average 13.7 knots using the Suez Canal.
The cost reduction will amount to $19m per service annually assuming that these Suez services sail 50 out of the 52 weeks of a year, SeaIntel estimated.
Carriers on average pay $465,000 for the passage through the Suez Canal of vessels deployed on the Asia-USEC services, according to SeaIntel citing sources. Hence, the Suez Canal would need to cut toll prices roughly in half to offset the cost reduction.
SeaIntel said that there are eight north Europe-Asia services that can incur savings using the south of Africa route. The services will incur an average extra fuel cost of $328,000 for going south of Africa but it will still be more economical compared to the average Suez Canal bill of roughly $730,000 per voyage for the vessels used.
While carriers are currently using the south of Africa route for the backhaul legs and retaining the transit time, SeaIntel said that switching to the said route on the headhaul “is going to look alluring for some carriers” given their current financial situation and the ease of implementing slow steaming.
“Not only would the carriers save the canal charges on the headhaul - slowing down the services by a week in each direction to go around Africa would soak up a potential 60-80 vessels, of which half would be mega-vessels,” SeaIntel said, pointing out that the move will address the current overcapacity.
SeaIntel added that if the longer-term bunker prices are expected to remain low, carriers may adopt the route change even on the headhaul, keeping fuel consumption and service speeds low by adding one to two weeks to the round trip.
Tapping the south of Africa routing on the backhaul leg of the Asia-USEC and Asia-north Europe services, however, comes with a cost to the environment. 
A vessel on USEC-Asia normally using the Panama Canal would emit an additional 5,100 tonnes of CO2 by sailing south of Africa while a ship sailing through the Suez Canal would  emit an additional 1,700 tonnes of CO2.
For the north Europe-Asia services where it is economically viable to switch to the south of Africa route, an additional 6,800 tonnes of CO2 on average would be emitted per voyage, SeaIntel added.