Is emissions policy on the wrong track?

Not a commercial debate

Dr Lindstad argued that while in theory using LNG reduces GHG emissions by about a quarter compared with MGO or HFO, larger emissions from the LNG supply chain and uncombusted methane from the ship’s engine can actually nullify GHG gains.

Currently, low-pressure Otto-cycle-based dual-fuel LNG engines represent the cheapest option in terms of capex for meeting regulations such as the EEDI’s energy efficiency requirements. However, Dr Lindstad said that such low-pressure LNG options actually increase global warming, having 137% of the WTW emissions of diesel marine gasoil (which Dr Lindstad used as a reference fuel) and not reducing GHG emissions at all.

Using as an example vessel a medium-range, 183 m-long tanker with a design dwt of 37,000, of which there are approximately 1,500 such vessels globally, Dr Lindstad noted that the best LNG technology available – high-pressure dual-fuel engines operating on the diesel principle – meet all regulatory requirements at a cost of about US$9M-US$10M. However, the cheaper option – the low-pressure Otto cycle – only costs about US$5M.

“With the current regulation, where CO₂ is the only gas included in the EEDI, with this option we meet all the requirements and we get the certificate saying that we have a 25% lower EEDI, but we will not save any GHG at all.”

She continued: “Business for manufacturers of these engines is booming but we’re not actually achieving our climate target; we’re on totally the wrong track.” Dr Lindstad agreed that “commercially, it makes sense”, but she emphasised “we’re not having this debate about what makes commercial sense; it’s about the need to try to limit global warming.”

By using HFO along with scrubbers, exhaust-gas recirculation systems and improved ship design – such as hydrodynamic enhancement and high-efficiency hullforms – fuel consumption could be reduced by 10%-20%, with comparable reductions in GHG emissions. This means such setups can play a part in reaching IMO’s 2050 targets. Dr Lindstad added: “The basic message is large diesel engines with scrubber and EGR, and after-treatment of the exhaust gas, allow us to run the engine on HFO and meet all the emission regulations.”

But a high-pressure dual-fuel LNG engine operating on the diesel principle, while more expensive than low-pressure Otto dual-fuel LNG, not only meets all regulations but gives a 15% GHG emissions reduction on its own, Dr Lindstad explained. When combined with more slender hullforms and hydrodynamic design, it can reduce fuel consumption by 10%-20%, depending on ship type, and reduce GHG emissions by 25%-35%, making a key contribution to IMO’s 2050 goals.

Beyond the sulphur cap: Energy-efficiency requirements out to 2050

• Energy Efficiency Design Index (EEDI)

Aimed at promoting use of more energy-efficient equipment and machinery, the EEDI has been introduced in several phases with more stringent requirements each time, which require vessels to demonstrate a minimum tonne-mile energy efficiency level, calculated depending on vessel size and segment. Phase 3 was originally scheduled for introduction in 2025 but has been brought forward to 2022, meaning vessels constructed after that date will need to demonstrate a design efficiency at least 30% lower than the reference line.

• Ship Energy Efficiency Management Plan (SEEMP)

Developed alongside the EEDI, the SEEMP is a ship-specific tool that is used by vessel operators to assess the current energy efficiency of a vessel and plot out how its performance can be optimised. Once the plan is in place, it is monitored using the Energy Efficiency Operational Indicator, a tool introduced by IMO that allows operators to assess fuel efficiency and the effect of changes in operation, such as improved voyage planning, more propeller or hull cleaning, or the use of other technical measures.

• NOx Tier III emission controls

Applicable to vessels operating in Emission Control Areas (ECAs) since January 2016, NOx Tier III emission standards also apply to vessels constructed after that date and from 2021 will apply to vessels larger than 24 m but below 500GT. NOx emission limits for a vessel are determined using a calculation based on a vessel’s construction date and engine speed.

• IMO’s 2050 carbon target

In April 2018, IMO’s MEPC committed to reducing the maritime sector’s CO₂ output by 50%. An interim target of a 40% reduction in carbon intensity in shipping by 2030 has also been set.