In its proposal to the 82nd meeting of the IMO’s Marine Environmental Protection Committee (MEPC 82), China has sought a provision to restrict residue or sludge to a minimum of <1%, according to Engine Technologies.
China argues that this is required to ensure that sludge or residue will not affect the total fuel oil consumption data that goes into calculating a vessel's CII rating.
“The maximum quantity of residue/sludge to be subtracted from the fuel oil consumption of a certain reporting period should be less than [1%] of fuel oil consumed,” China’s proposal reads.
Currently, the quantity of fuel oil residue or sludge may vary based on fuel oil quality, type of operation and other factors, China claims.
China conducted a study on fuel oil residue or sludge from 13 ships sailing internationally. It found that the proportion of oil residue or sludge was in the 0.39%-2.26% range, and was likely to increase due to the poor quality of some blended fuels.
The country argues that since it was difficult to determine an accurate estimate, an "upper limit" is therefore recommended for the fuel oil residue or sludge. With this recommendation, China asserts that a vessel’s fuel consumption data during the data collection phase can be corrected to avoid errors during CII calculation.
The annual fuel oil consumption is one of the factors used to calculate a vessel’s carbon intensity indicator (CII). The CII rating assesses a vessel’s carbon emission intensity over a period of time.
Sludge content in fuel oil is not directly regulated, but it is indirectly controlled using various other parameters, such as total sediment potential (TSP), which influence sludge formation in the fuel.
As per the ISO 8217 2017 fuel standard, the maximum TSP content by volume has been set at 0.10% for marine residual fuels. High TSP levels can make fuels unstable and cause sludge to form in fuel tanks, treatment and injection systems, potentially causing engine damage.
China’s proposal will be discussed at the IMO’s MEPC 82, which will convene in London between 30 September and 4 October.