Methane Slip Emissions from Ships:

summary based on measurement data

Sergey Ushakov, Norwegian University of Science and Technology

Dag Stenersen, SINTEF Ocean

Per Magne Einang, SINTEF Ocean

2

Outline

• Introduction– Global shipping overview

– Regulations and future solutions for lower emissions

– LNG as marine fuel and available gas engine technologies

• Study on methane slip from ships– Overvier and limitations

– Results for LBSI and LPDF engines

• Summary and conclusions

Image source: www.iea.org International Energy Agency, photo: Getty Images

3

Global shipping

Image source: Balcombe et al. How to decarbonize international shipping: Options for fuels, technologies and policies. Energy Conversion and Management

182 (2019) 72-88.

• Shipping is responsible for 80-90 % of

the world’s trade

• Most cost- and energy-efficient way of

commercial transport– 3.2 Mt of NOx emitted ( <5% of global)

– 2.3 Mt of SOx

– 1.1 Gt of CO2 (around 3% of global)

• Diversity of ship classes/sizes operating

with different operating profiles– Biggest vessels are the most efficient in terms

of gCO2/tonne-km, but are the biggest

pollutants

4

Regulations and

emission reduction

• SOx emissions

– Tightening global sulfur cap: 0.5% S from 2020

– More Emission Control Areas (ECAs)

• NOx emissions

– Tightening regulations: Tier III for new-built

• CO2 emissions– Energy Efficiency Design Index (EEDI): design measures

– Ship Energy Efficiency Management Plan (SEEMP):

operational measures

– IMO’s 2050 50% GHG emission reduction target

• Market growth should be considered

• New (lower carbon/zero carbon) fuels have to be used

5

Transition paths

Sources (upper left, * data): N. Olmer et al. Greenhouse gas emissions from global shipping, 2013-2015. ICCT, 2017

(lower left): Psaraftis and Kontovas, CO2 emission statistics for the world commercial fleet, WMU Journal of Maritime Affairs, 2009

Crude oil carriers

86%

HFO

HFO

HFO

Diesel

HFO

Biofuel /(bio) LNG / NH3 /H2

SCR

EGR + scrubber

IMO’s CO2 target for 2050 is 50 % reduction per tonne-km

≈3% of global

CO2 emissions*

HFO Fuel cell (H2)

HFO Battery

ICEs

non-ICEs

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Feasibility of available solutions

7

LNG as alternative marine fuel

(Right chart *) - numbers are based on seach algorithm through the final programmes using the keywords gas, methane, dual fuel, lean burn, etc.

*

Methane slip

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Three main gas-fuelled engine

concepts• LNG is the only alternative fuel currently

available for deep-sea shipping

• Fuel flexibility is essential for bridging

technologies towards carbon-free shipping

• HPDF concept is fuel flexible and has no

methane slip-related issues

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Key characteristics of

gas engine concepts

• LBSI, medium speed– Rolls-Royce Bergen Engines (NO)

• LBSI, high speed– Mitsubishi (JP)

• LPDF, medium speed– Wärtsilä (FI)

• LPDF, low speed– Win-GD (CH)

• HPDF, medium speed– Wärtsilä (FI) – on-land application only

• HPDF, low speed– MAN Diesel and Turbo (DE)

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Frames of current measurement

study• Marine gas engines

– Medium speed, 4-stroke

– LBSI and LPDF

– Different gas technology generations

• Methane slip– Additional measurements of NOx and

other emissions

• Measurement data– Test-bed vs. on-board

– E2 and E3 cycles

• Different fuel composition– Methane number variation considered

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LBSI engines

• Same engine model– Test-bed: LBSI9 (E2), LBSI10 (E3)

– On-board: LBSI8

– LBSI1 – old gas engine technology (prior 2010)

• Expected emission trends– With load increase: better combustion due to

increasing fuel-air ratio

– NOx ↑, CO and CH4 ↓

– Tier III requirements are fullfilled

• Challenging low load conditions– Incomplete combustion due to very lean

conditions

– Additional effect from variation in fuel

composition, operational state, etc.

• Important to consider vessels’

operating profile (vessel type)– LBSI1 – passanger/car ferry

Overview

Same engine model, different ships

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LBSI engines (cont.)

LBSI9 LBSI8

• No evidence of methane slip in case of

test-bed measurements– CH4 emissions peak only at 10% load

– Laboratory infrastructure: better control of test

conditions and possibilities for tuning

• Possible LBSI8 engine «overtuning»

for low NOx

– Final engine tuning, based on on-board

measurements under real operation, can be

proposed

• Good stability of measurement results

for the most of the considered engines– Extensive planning and equipment preparation

– Shipowners are interested in results in order to

optimize engine/ship performance

– Need for field testing for better evaluation of

different gas technologies

Same engine model

13

LPDF engines

• Test engines– Test-bed: LPDF2

– On-board: LPDF1 (E3), LPDF3 (E3)

– LPDF1 and LPDF2 – same engine model

• Challenging low load conditions – also

for presise measurements– Unstable combustion (keep in mind amount of

pilot fuel) and effect of actual load variation

– Below 25% load - large variation in results

• Expected emission trends (as for

LBSIs)– With load increase: better (and more stable)

combustion due to increasing fuel-air ratio

– NOx ↑, CO and CH4 ↓

– Tier III requirements are fullfilled (with the

exception of LPDF1)

Overview

Same engine model

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LPDF engines (cont.)

• Generally higher NOx emissions that

from LBSI engines– Effect of pilot fuel (important for maintaining the

stability of the combustion)

– Although, controlling the amount of pilot fuel

injection can be used to control methane slip

• Clear indication of low NOx tuning at

75% load– Highest weighting factor (0.5) according E2

and E3 test cycles – need for compliance

– Lower margin can be used – possibility for

optimization

• Variation in cylinder power rating has

only a minor effect on methane slip at

loads above 50%– Considerable effect at lower loads

– The opposite effect on NOx emissions

Same engine model

Same engine model

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LBSI and LPDF: summary

• Test engines– Modern LBSI and LPDF

– Older (prior 2012) LBSI

• Both LBSI and LPDF engines achieve Tier 3

compliance without aftertreatment– Tuning of engine for low NOx has to be used

• Higher NOx emissions from LPDF engines– Amount of pilot fuel has to be considered

• Higher methane slip from LPDF engines– Major part is believed to be a consequence of lean

operating conditions

– Fuel quality (methane number) is also essential

• Huge progress in gas technology during the

last 5 years– Methane slip has been reduced for both LBSI and

LPDF engines by around 50%

• Methane slip regulations in the future?

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Summary

• LNG as marine fuel is one of the most promising options («transition fuel» towards full decarbonization)

– Technology is available (only infrastructure is delayed)

– Fullfilling both NOx and sulfur regulations, lower CO2 emissions

– Methane slip is one of the problems to be solved (??? use of HPDF ???)

• Large difference in both NOx and methane slip emissions measured in lab and at sea

– Low loads (below 25%) are especially challanging

– Better control of test conditions in laboratory and possibilities for additional engine tuning

• Overtuning of the engine for lowest NOx results in excessive (and unnecessary) methane slip

– Minimize margins used

• Standard E2 and E3 test cycles is not a perfectsolution for covering all vessel types

– Operational pattern is vital to consider

Image source: www.klawlng.com, LNG vessel bunkering, accessed May 2019

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Thank you for your attention!

Any questions?

Image source: www.toonpool.com