MORE than 30 years after governments first started to regulate nitrogen oxide (NOx) emissions from shipping, international experts are increasingly concerned that the rules developed are simply not working.

A complex series of policy flaws, data manipulation, compliance failures and industry avoidance tactics are thought to lie behind the various failures.

But as governments race to address the likely increased output of NOx and nitrous oxide from a sector-wide shift towards zero-carbon fuels yet to enter the market, the mistakes of the past are now jeopardising the roll-out of policy yet to be drafted.

Strict limits on NOx emissions from marine diesel engines have been in place internationally since 2016, when amendments to the International Convention for the Prevention of Pollution from Ships (Marpol), first started in 1991, entered into force.

The revisions effectively applied NOx limits to ships built after 2000 on a tiered basis, with the most stringent measures (Tier III) applied to engines installed on ships with keels laid on or after January 1, 2016.  

However, the warning signs that those rules have not been working properly have been bubbling up through technical reports for several years and have now triggered a wholesale regulatory review.

Compliance loopholes

In February 2023, a report submitted to the International Maritime Organization by Canada examined the effect of low-load operation on the performance of NOx Tier III technologies.

The results raised serious questions regarding the difference between the assumptions made in the NOx Technical Code and the real-world operation of ships within Emissions Control Areas.

The data suggest that ships spend between 25% and 35% of their operational time below 25% engine load, where NOx emissions-reduction technology may be completely disengaged or operating inefficiently.

That implies the engine test cycle standards, as they are set up today, are completely inadequate and failing to control emissions below 25% power.

Ship operation analysis for 2021 submitted to the IMO by the US shows that approximately 38% of Tier III engine operation was below 25% load, where the various technologies that reduce NOx are likely to be disengaged.

The NOx Technical Code allows for the so-called ‘selective catalytic reduction’ (SCR) — a  technology that can help meet NOx Tier III standards — to automatically disengage when the engine power drops below 25%.

While the SCR unit may be capable of operating below that power point, there is a cost incentive for owners not to use it, because disabling the SCR at low power means the ship operator does not need to use reductant during that operation — thus saving on operational costs within the letter of the regulations as they are written.

There was also a commercial loophole built into the various cut-off points for rules to apply to ships, linked to the date a ship’s keel is laid.

When the North American ECA was adopted, there was some concern that shipowners would forego building Tier III-compliant ships, choosing instead to send their older ships to the US and Canada. While that behaviour did occur, it was to a much lesser extent than expected.

Instead, the bigger problem was that shipyards took advantage of compliance being linked to keel laying to lay massive numbers of keels in 2015 to avoid having to install Tier III engines in ships being built from 2016.

Despite the compliance loophole being well documented, the same issue was still in place for 2020 keels to avoid the Tier III standards in the Baltic and North Sea NOx ECAs.

Then there were the various compliance issues that have repeatedly highlighted the gap between paper compliance and real-world implementation of regulations.

While continuous emissions monitoring was considered during the discussions of the original 2008 amendments to the rules, the final programme opted for a certificate-based approach via the standard Engine International Air Pollution Prevention (EIAPP) certificate.

“Unfortunately, this approach has proven to be quite ineffective, as port State control officers are often limited to paperwork inspections to verify compliance, even in those cases where there are reasons to believe there was non-compliance based on remote sensing or other information,” concluded a report submitted to the IMO earlier this year by the rapidly growing coalition of states concerned about NOX rules.

That group now includes Belgium, Canada, Denmark, Germany, Ireland, Netherlands, Norway and the US, with various other states also now starting to voice serious concerns. 

The weak compliance approach can motivate emissions violations, argue the concerned states — especially if the violations cannot be detected through paperwork.

Tier II engines are also limited to paperwork compliance, even though modern electronically controlled engines can also be adjusted just by another engine operational profile to fall out of compliance.

“In sum, shortfalls in the compliance procedures means that it is difficult to detect possible violations by ships that are equipped with Tier III, and/or even Tier II engines and their NOx-reduction technology, even in cases where high NOx emissions are observed through remote sensing,” concluded the IMO submission.

Fraudulent testing

The shortfalls in the paperwork compliance approach were also highlighted earlier this year, when the Japanese government was forced to order a sector-wide investigation into fraudulent fixing of engine test data among manufacturers.

Four Japanese manufacturers have admitted to falsification of fuel consumption data measured during test runs dating back as far as 1999.

The Japanese government investigation is ongoing; however, the evidence already published makes clear that manufacturers were manipulating specific fuel consumption data to align with promised customer specifications.

While NOx emissions data were not the intended target of the falsifications, the changes made to fuel figures essentially rendered the NOx numbers, at best, unreliable — and, in some cases, a work of fiction.

The engine data scandal is not simply a matter of commercial reparations and the outcome of the Japanese government ultimate investigation; it points to a significant conflict between flag states and their designated ‘recognised organisation’ — generally speaking, classification societies.

The certificates or approved documents are issued by the flag state, or by one of its ROs and the established NOx technical code clearly outlines the survey and certification scheme that ROs must follow.

However, ROs are not in a position to act in the same way as official authorities for policing alleged fraudulent behaviours.

Senior class officials point out that the regulations are designed to be adopted and implemented on the basis they will be adhered to. “If there is outright fraud, as is alleged, the system breaks down,” explained the class official.

Rip it up and start again

The net result of these various loopholes and policy failures have prompted the IMO to undertake a wholesale review of the rules, which several governments have now stated openly are not having the intended effect.

That review, however, will not commence until a sub-committee gets around to considering the issue in 2026.

Retrospectively amending flawed policy is only a minor part of the agenda being pushed by those states concerned that the regulations are not working.

The more immediate concern is having an effective NOx control programme in place before the shipping industry starts moving rapidly towards zero- and near-zero-carbon fuels.

As the Belgium paper submitted to the IMO has already pointed out, “at least some alternative fuels (fatty acid methyl ester biodiesel, methanol, hydrogen, and ammonia) may have different NOx emissions than marine diesel fuel, which could affect compliance with both the Tier II and Tier III standards”.

It is also now a serious concern that nitrous oxide (N2O), which is a by-product of combustion, is generally recognised as having much greater global warming potential than CO2 — and its emissions can be adversely affected by improperly designed NOx-reduction technologies.