Report: Scrubbers Have Lower Climate Impact Than Low-Sulfur Fuels

As the shipping industry continues to debate the best means of meeting the 2020 sulfur reduction regulations, the independent environmental research consultancy CE Delft is releasing a new study that concluded that the use of exhaust scrubbers produces slightly lower CO2 emissions versus using very low sulfur fuel oil (VLSFO) on a range of vessels.

According to Delft, the objective of the study was to compare the CO2 emissions of two ways to comply with the sulfur regulation: using the technology commonly referred to as scrubbers in combination with high-sulfur fuels or using low-sulfur fuels. The comparison was conducted on a well-to-wake basis, implying that all GHG emissions over the lifecycle of both compliance options are considered. In this way, a full-integrated comparison of the CO2 emissions of both options has been carried out.

Acknowledging that preceding studies demonstrated uncertainty about the environmental impacts of the use of scrubbers, both about which environmental impacts are relevant, how large the impacts are, and about how they should be judged, Delft set out to provide factual input to the debate. The study was commissioned by three major scrubber suppliers.

“This study provides a comprehensive overview of the climate impacts of different options to reduce sulfur emissions,” says project leader Jasper Faber. “It shows that in many cases, the carbon footprint of using a scrubber is lower than low-sulfur fuels.” 

The comparative analysis of using low-sulfur fuel versus deploying scrubbers was carried on five reference ships that Delft reports are a good reflection of the main ship types that currently have installed scrubbers or which have a large demand for scrubbers. They include: 100,000 GT cruise ship; 4,000 TEU container ship; 18,000 TEU container ship; 80,000 dwt bulk carrier; and 200,000 dwt oil tanker. The report models two primary cases looking at a range of variables in fuel quality and scrubber installation and operation.

The CO2 emissions associated with using an exhaust gas cleaning they judge as varying between 1.5 and 3 percent. However, they find that in many cases, the emissions caused by producing low-sulfur fuels for these ships are higher, depending on the quality of the low-sulfur fuel, the refinery, and the crude oil slate. 

Both options however result in an increase of well-to-wake CO2 emissions according to Delft. They outline that a scrubber requires energy which is generated by engines running on fuel oil and thus produces CO2. Also, there are emissions associated with manufacturing scrubbers and emissions from the seawater. The analysis determines that the use of scrubbers results in an increase of CO2 emissions between one and a half and three percent for a range of representative ships. 

Desulphurization in a refinery on the other hand requires hydrogen which is generally produced from methane, emitting CO2 in the process, as well as energy. They note that desulphurization leads to an improvement in the fuel quality in terms of aromatics content and viscosity. They, however, conclude that the increase of emissions associated with desulphurization in a refinery is higher than one percent and in many cases multiple times higher, depending on the quality improvement of the fuel, the refinery layout, and the crude used.

The complete report with a detailed analysis is available to be downloaded on the CE Delft website.