The IMO's decision to implement a 0.50 percent global sulfur cap on marine fuel from 2020 could result in an overall increase in emissions of CO2.
That’s the conclusion drawn by Gustav Krantz, author of a new study published by Trans Oleum, an independent consulting company providing services on fuels, transportation and environment.
A majority of ships operating in the Baltic Sea, the North Sea and the English Channel switched to marine gas oil or marine diesel from January 2015 to comply with sulfur emission control area regulations.
As a consequence, air borne sulfur emissions have decreased drastically. The fuel sulfur content does not generally add to the heat value of the fuel so is not correlated to emissions of CO2. Simply switching fuel should therefore only have minor effects on overall CO2 emissions from a “tank-to-propeller” perspective.
Several studies indicate only minor changes in greenhouse gas emissions as a result of the fuel switch. However, the CO2 equation changes when refinery operations required to meet the demand for low sulfur fuels are considered, says Krantz. The increase in CO2 emissions can be detected when observing refinery crude oil intake, pre and post the new regulation as demand switches from a low value to a high value oil product.
Krantz argues that the increase in indirect emissions of CO2 has been severely underestimated, with a theoretical increase of 112 million tons of CO2 and statistical support for 93 million tons of CO2 per annum caused by the fuel switch.
Shipping companies that have installed scrubbers do not contribute to increased indirect CO2 emissions, says Krantz. Incentives for reducing CO2 should therefore be directed to increase the use of scrubbers.
The study is available here.