Hong Kong's enthusiasm for clean air has spread to neighbouring Shenzhen, where the government plans to spend RMB200m ($32.6m) a year on cash rebates to encourage shipping lines to switch to low sulphur fuel while at berth, local media reported.

Emulating Hong Kong's earlier subsidies scheme, the Shenzhen government will subsidise 75% to 100% of the extra costs incurred by the lines in the voluntary scheme. It will kick in next month and last for three years.

"We are learning from the experiences in Hong Kong where companies have volunteered to switch to low sulphur fuel and the government provides subsidies for extra costs incurred," Dong Yangze director of Construction Management Office of Shenzhen municipality's Transport Commission was quoted as saying.

In addition, Shenzhen is also pushing to set up an emissions control area that would cover the Pearl River Delta by 2018, Li Shuisheng deputy director of Shenzhen's Human Settlements and Environment Commission said.