Suggested Citation:
Wan, Zheng, Mo Zhu, Shun Chen, Daniel Sperling (2016) Pollution: Three Steps to a Green Shipping Industry. Nature 530 (7590), 275 - 277

Ever bigger container ships carry 90% of global consumer goods such as clothes and food (non-bulk cargo). The seaborne container trade has grown from 100 million tonnes in 1980 to about 1.6 billion tonnes in 2014. Standardized 20-foot (6-metre) containers are moved using automated systems that connect seaports, airports and train stations. Bigger ships carry more containers, ideally consuming less oil and releasing fewer pollutants for each unit of goods carried.

Nonetheless, the human and environmental costs of shipping are vast. Low-grade marine fuel oil contains 3,500 times more sulfur than road diesel. Large ships pollute the air in hub ports, accounting for one-third to half of airborne pollutants in Hong Kong, for example. Particulates emitted from ships cause 60,000 cardiopulmonary and lung-cancer deaths each year worldwide. Expanding harbours to take vast ships destroys coastal ecosystems. And scrapping fleets of obsolete smaller ships pollutes seas and soils, and damages workers' health, especially in the developing world.

The industry is at a crossroads. The expected profits from larger ships are being undermined by excess capacity, slowing trade and plunging transport prices. In 2015, container freight rates for the world's busiest shipping route — between Asia and northern Europe — dropped by nearly 60% in three weeks. A dozen shipping companies went bankrupt, including Denmark's Copenship and China's Nantsing. Even the giant container-conveying Danish conglomerate Maersk announced that it would lay off 4,000 employees by 2017 and delayed or cancelled orders to build mega-ships.

Companies face a dilemma. If they buck the trend of scaling up, they risk being less competitive. Yet running mega-ships only part full wipes out the benefits of economies of scale. Ships use more fuel per container when half loaded than for a full cargo.

The future is green shipping: efficient marine transport with minimal health and ecological damage. Cleaner practices — especially on ship scrapping, emission control and port management — are needed. Achieving this will require heroic efforts by the industry and its engineers in collaboration with regulators, port authorities and communities. Environmental impacts should be considered in determining optimal routes and modes for delivery of goods.