Are scrubbers really good for the environment?

THERE are two main challenges facing shipping that relate to emissions. In just over four months' time, a global sulphur limit of 0.5 per cent for marine fuels will come into force. That is centre stage right now.

In the longer term, the much more challenging task will be to drastically cut CO2 (carbon dioxide) emissions from ships.

These are different challenges but there are clear policy overlaps for governments and for shipowners. For example, the use of liquefied natural gas (LNG) has been mooted as not only solving the sulphur problem but also acting a bridging fuel towards a carbon- free future.

There have been challenges to this view, often based on the issue of "methane slip" where a portion of the natural gas escapes into the atmosphere during the extraction process. However, LNG is certainly making significant headway as the "green" alternative.

On the other hand, the idea of continuing to burn high-sulphur fuel oil (HSFO) and then using a scrubber to remove sulphur particles from the emissions stream has generally not received an enthusiastic response from the environmental campaign groups. Usually, it is at best seen as a pragmatic short-term, relatively cheap way of meeting the regulations.

That is why some research findings from one of Europe's largest independent research organisations, Norway's SINTEF, are likely to be controversial. SINTEF's chief scientist Elizabeth Lindstad has concluded that the continued use of heavy fuel oil with a scrubber is the most environmentally beneficial means of meeting global greenhouse gas (GHG) emissions targets.

That will be not well received by those advocating the LNG option. They consider LNG to be the most beneficial of existing options. However, it must be said that Dr Lindssrad did not look specifically at the LNG option nor said that it is not an effective way forward.

These findings are being publicised by the Clean Shipping Alliance 2020 (CSA 2020). Formed in September last year, it describes itself as representing a "large group of leading companies from the commercial and passenger shipping industries that have been leaders in emission control efforts through significant investments in research and analysis, funding and committing resources to comply with 2020 fuel requirements through the development and use of exhaust gas cleaning systems (EGCS)".

Not surprisingly Dr Lindstad's conclusions have gone down very well with CSA 2020 members.

Full-scale testing

According to CSA 2020, after detailing findings from research involving full-scale testing on a number of newbuild vessels, Dr Lindstad found that " two-stroke engines with Exhaust Gas Recirculation (EGR) and scrubbers represent the most cost- and GHG-effective way of meeting both IMO (International Maritime Organization) Tier 3 NOx (nitrogen oxides) rules and the 2020 sulphur cap".

Dr Lindstad said that based on the energy consumed during the global production of distillate fuels, the continued use of residual fuel would have a positive impact on global GHG emissions, given that the energy required to produce distillates would result in higher levels of CO2 being released into the atmosphere.

She explained: "With new modern refineries set up to convert crude into higher-priced products, HSFO will, from 2020, be delivered from existing refineries where its share of energy consumption can be considered to be next to nothing. The explanation is that the heavy bunker oil coming out from the refinery is the bottom of the barrel. If we acknowledge the lower energy consumption in delivering HSFO and deduct the refining, we get 9-10 g of CO2 equivalent per MJ (megajoules) for HFO (heavy fuel oil), rather than 13 to 15 of CO2 equivalent per MJ for LSFO/MGO (low sulphur fuel oil/marine gas oil)."

Dr Lindstad also believes that emissions abatement rules need to be reviewed to consider pollution problems in different areas. "To meet climate targets, that is, reduce global GHG emissions, we can no longer afford to have standards that are strict in areas where we do not have local pollution problems, while areas with high pollution may need even stricter rules than today," she told CSA 2020.

Ian Adams, executive director of CSA 2020, said the industry has long realised that there is an energy penalty differential in the production of fuels. He said: "Using higher sulphur fuels with an exhaust gas cleaning system will have a beneficial impact on the global reduction of sulphur and nitrogen oxides emissions, and also on greenhouse gas emissions."

According to Mr Adams, there is also a significant benefit from reduced particulates in emissions. "With reduced particulates in exhaust emissions of 75 per cent or more, the combination of dramatically reduced SOx (sulphur oxides) and particulates makes a big difference in improved air quality and lower health risks," he said.

"This study provides further scientific evidence that both local SOx and NOx to air and global CO2 emissions will be reduced by the expanded use of HFO with exhaust gas cleaning systems in the marine fleet, with benefits to the marine and port environments and, of course, human health," concluded Mr Adams.

Well, stand by for a counter blast from the alternative fuels lobby. Still, Dr Lindstad's findings will be good news for those shipowners who have chosen the scrubber route 2020 compliance.