The Ministry of Ecology and Environment will introduce new regulations on ship exhaust smoke limits and measurement methods to strengthen the control and management of pollutant emissions from in-use ships.
Reporters learned from the Ministry of Ecology and Environment that the national ecological environment standard “Ship Exhaust Smoke Limits and Measurement Methods (Draft for Comments)” has begun public consultation and is expected to be introduced in the near future. The standard is undertaken by the China Classification Society, with participating units including the Chinese Research Academy of Environmental Sciences, the Tianjin Research Institute for Water Transport Engineering of the Ministry of Transport, and the Shanghai Academy of Environmental Sciences. This standard applies to ships navigating or berthing in waters under the jurisdiction of the Chinese government, targeting black smoke emissions caused by improper maintenance of diesel engines and improper matching of the ship, engine, and propeller during ship operation.
According to statistics from the “2024 Statistical Bulletin on the Development of the Transport Industry,” by the end of 2024, the country had 110,200 water transport vessels, completing a total of 9.811 billion tons of commercial freight volume throughout the year, an increase of 4.7% over the previous year. By the end of 2024, the navigable mileage of national inland waterways was 128,700 kilometers, an increase of 528 kilometers from the end of the previous year. By the end of 2024, there were 22,219 port production berths nationwide, an increase of 196 from the end of the previous year.
During operation, ship engines generate a large amount of exhaust gas due to fuel combustion. The exhaust contains pollutants such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), sulfur dioxide (SO₂), and particulate matter (PM), which pose serious threats to the environment and human health.
According to statistics from the “China Mobile Source Environmental Management Annual Report (2024),” in 2023, ship emissions of HC, NOx, and PM were 111,000 tons, 1.6186 million tons, and 64,100 tons, accounting for 27.4%, 35.7%, and 28.6% of the total non-road mobile source emissions, respectively. The above statistics show that the total amount of major air pollutants emitted by ships is on an upward trend.
“Black smoke emissions from ships will significantly increase the particulate matter content in ship exhaust, seriously affecting ambient air quality. Therefore, it is very necessary to control air pollutant emissions from ships, especially to control particulate matter and even black smoke emissions from operating ships,” stated the drafting instructions for the征求意见稿.
Ship Air Pollutant Emission Control Areas have already implemented stricter standards. The picture shows the chimney of an ocean-going cargo ship. /Ke Zhang
The drafting instructions explain that in recent years, with the implementation of emission regulations, the emission levels of newly produced ships have gradually improved, playing an important role in strengthening source prevention and control of ship emissions and promoting progress in emission control technology. In particular, the release and implementation of “Limits and Measurement Methods for Exhaust Pollutants from Marine Engines (China Phase I and II)” (GB15097-2016) have effectively improved the emission control levels of inland river and coastal ships.
However, the current standards do not account for severe exceedances of diesel engine smoke density in actual ship use due to improper maintenance or improper ship design and selection, leading to visible black smoke. Furthermore, according to the current standards, testing exhaust smoke density requires boarding the ship and installing testing equipment on the ship’s diesel engine exhaust pipe. The testing method is complex, enforcement is difficult and costly, making it hard to implement in maritime supervision or environmental protection oversight.
Industry experts explain that there are three main reasons for ship black smoke: a sudden increase in diesel engine load, causing a temporary excess of fuel over air in the cylinder and incomplete combustion; unreasonable matching of the ship, engine, and propeller, causing the diesel engine to be overloaded; and improper maintenance of the diesel engine, such as severe wear of the fuel injection pump plunger or valve, poor fuel injector atomization, or clogged intake pipes.
According to the draft for comments, to meet the demand for stricter standards in Ship Air Pollutant Emission Control Areas, the new standard stipulates that relevant emission control areas may choose to implement Ringelmann smoke number (an indicator for assessing soot emission concentration) level 1. Regions with adequate enforcement conditions are encouraged to adopt stricter limit standards. The standard recommends using Ringelmann smoke number level 2 as the compliance standard. Within emission control areas, depending on the maturity of conditions, Ringelmann smoke number level 1 may be chosen as the compliance standard.
The drafting instructions state that if Ringelmann level 2 is used as the compliance standard, based on the 110,200 water transport vessels nationwide reported in the “2024 Statistical Bulletin on the Development of the Transport Industry,” approximately 220 merchant ships might not meet the standard limit requirements, which would have little impact on the shipping market. The implementation of this standard will promote the normal maintenance level of ships, reduce black smoke emissions, and thereby improve ambient air quality, especially in port cities.
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