Sustainability of cruise ship fuel systems: Comparison among LNG and diesel technologies

https://doi.org/10.1016/j.jclepro.2020.121069Get rights and content

Highlights

  • Sustainability assessment of LNG and diesel fuel systems for cruise ships was carried out.

  • Sustainability evaluated through environmental, economic, and safety impact indexes.

  • LNG systems offer better sustainability profile than diesel fuel (35% impact decrement).

  • Reduced environmental (41%) and economic (31%) impact of LNG compared to diesel.

  • Safety index 62% higher for high pressure LNG systems compared to diesel.

Abstract

Liquefied natural gas (LNG) is becoming a viable, “green” alternative to marine fuel oil for ship propulsion. The present study investigates the expected impact on sustainability of innovative ship fuel systems based on the use of LNG. For the sake of comparison, conventional technologies for ship fuel systems, based on marine fuel oil, were considered in the analysis. A specific methodology was adopted to support the sustainability assessment, based on the evaluation of key performance indicators addressing three fundamental domains: environmental impact, economic feasibility and inherent safety of the fuel system. The results obtained allow determining a sustainability fingerprint of the alternative fuel systems considered and a performance ranking. The LNG-based fuel system technologies show a better sustainability performance than the conventional marine fuel technologies. The relevant environmental benefits associated with LNG fuel systems point out the critical role of environmental impact reduction in driving the design of innovative fuel systems for marine applications.

Introduction

By the end of the twentieth century, the International Maritime Organization (IMO) started addressing the environmental impact caused by marine activities, adopting MARPOL Annex VI, which introduces emission limits for SOx and NOx (Thomson et al., 2015). Viable solutions to achieve the emission reduction goals can be the adoption of exhaust gas treatment systems, the switch towards alternative cleaner fuels (Horvath et al., 2018), or measures aimed at the improvement of energy efficiency (Zhang et al., 2019). Recent trends in international emission regulations, technology development and shipping economics make liquefied natural gas (LNG) an increasingly attractive marine fuel, especially for the Mediterranean area (INERIS, 2019). Switching to natural gas can allow a relevant reduction in SOx emissions, along with negligible emissions of NOx and particulate matter (PM). Moreover, a CO2 emission reduction up to 25% may be achieved if LNG is used since it is less CO2-intensive than fuel oil (Helfre and Boot, 2013). However, as pointed out by Gilbert et al. (2018), lifecycle emission of LNG also include possible methane slips, which have an extremely high greenhouse effect potential. Thus, comprehensive evaluations of potential environmental impacts are crucial for the widespread utilization of LNG-based technologies (Gilbert et al., 2018; Jeong et al., 2018; Mallapragada et al., 2018).

Since 1970’s, LNG was used as a fuel in LNG carriers. In these applications, the boil off gas produced inside the LNG tanks is used in traditional boiler/steam turbine systems (Curt, 2004). More recently, the Baltic region states have pioneered the use of LNG as a ship fuel in ferries and offshore service vessels for the oil and gas industry (Canadian Natural Gas Vehicle Alliance, 2015). Moreover, North Sea states and especially Norway played an important role in the widespread utilization of LNG for ship applications in the last 13 years. According to DNV GL (2019), 43% of the total LNG-fuelled ships were based in Norway in 2016. The number of LNG-fuelled ships is growing and large vessels, including bulk carriers and cruise ships are under construction (Speirs et al., 2019).

According to the International Energy Agency (IEA, 2019), due to the growing power demand of Asian countries, an overall market growth is occurring, requiring production diversification on the supply side. For instance, the exploitation of cost-competitive shallow gas will increment the LNG exportation from USA, potentially reaching current levels of Qatar and Australia (McKinsey, 2018). This trend induces the evolution of contracts and prices, with potential fuel costs reduction. Speirs et al. (2019) estimated that the higher capital costs for dual fuel or gas propulsion systems may be recovered between 5 and 16 years payback period for ships considering current price regimes.

During the last 10 years, a number of different studies addressed environmental impact associated with ship emissions (Trozzi, 2010; Maragkogianni and Papaefthimiou, 2015; Anderson et al., 2015; Feenstra et al., 2019) and related environmental benefits of LNG as marine fuel (Banawan et al., 2009; Burel et al., 2013; Baresic et al., 2018; Deniz and Zincir, 2016; Hansson et al., 2019). Technical economic and environmental studies were proposed for LNG fuelled ships (Livanos et al., 2014; Schinas and Butler, 2016; Stoumpos et al., 2018), and sustainability studies based on lifecycle assessment were proposed (Brynolf et al., 2014; Ren and Liang, 2017; Trivyza et al., 2018).

Despite the growing interest in the analysis of LNG fuel ship sustainability fingerprint and performance (Burel et al., 2013; Ren and Liang, 2017; Ren and Lützen, 2017; Hansson et al., 2019), the available technical and scientific contributions mainly focus on single aspects of the potential impact of switching towards LNG-based technologies. A comprehensive assessment of economic, environmental and safety aspects of alternative LNG-based fuel systems is still lacking and the contribution of each aspect to the overall sustainability performance of such technologies was not yet evaluated. Moreover, a structured comparison among LNG fuel systems and conventional technologies, based on marine gas oil (MGO), is not present in the literature considering the holistic assessment of environmental, economic and safety aspects.

The present study focuses on the comparison of the sustainability performance of alternative fuel systems for large cruise ships. Several alternative technologies based on LNG and conventional fuels, such as MGO, were evaluated. The sustainability performance was defined as the integrated profile of environmental, societal and economic performance of the alternative fuel systems (Sikdar, 2003). In order to achieve the integration of the three aforementioned domains, a specific methodology based on the definition of key performance indicators (KPIs) was adopted. Reference criteria were developed to normalize and aggregate the performance indicators. An overall sustainability indicator was defined to compare LNG and MGO alternatives in order to rank the sustainability performance of alternative reference fuel systems and to identify critical elements in each option.

Section snippets

Overview

A specific approach was adopted to compare safety and sustainability of alternative ship fuel systems for large cruise ships, providing guidance in early-stage design. The approach was derived from a previous study (Tugnoli et al., 2008b), aimed at the assessment of manufacturing processes. A specific set of impact indicators was defined, covering the three main domains considered for sustainability assessment, i.e., environmental, societal and economic domain. The detailed description of the

Definition of reference schemes for alternative fuel systems

In order to provide a common basis to compare the sustainability of different fuel systems, a reference ship category and type was selected. A Hyperion-class cruise ship (The Maritime Executive, 2016) was chosen as a representative case study. Table 4 reports the ship characteristics considered in the following, obtained from vessel register database (DNV GL, 2018). Data in Table 4 were used to define the reference technology schemes of the alternative fuel systems considered.

In particular,

Single impact (level 1) indicators

The details on the assessment of single impact (Level 1) indicators and related input data are reported in Appendix A, based on the methods described in Section 2.2. A summary of Level 1 indicators (not normalized) for the alternative fuel systems is shown in Table 5.

The environmental indicators clearly point out the advantage of LNG-based fuel systems (Schemes 1, 2 and 3) in reducing the pollutant emission with respect to conventional technologies (Scheme 4). In particular, total SOx emissions

Discussion

The calculated KPIs show the overall excellent performance of LNG-based technologies compared to MGO (Scheme 4), in accordance with previous studies dealing with the sustainability assessment of alternative marine fuels (Burel et al., 2013; Ren and Liang, 2017; Hansson et al., 2019). This is due to the negative environmental profile of Scheme 4, which also downgrades its economic appeal due to the taxations considered.

Comparing the single LNG-based alternatives, Scheme 1 (low pressure dual

Conclusions

A sustainability assessment was carried out to compare the early design of alternative ship fuel systems based on either LNG or on conventional diesel fuel (MGO). A multi-criteria analysis was performed, considering the three main domains of sustainability: environment, economics and safety. KPIs were calculated and further aggregated into an overall sustainability impact index.

The results showed that LNG-based technologies offer a better sustainability performance than MGO (scheme 4). Low

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Authors gratefully acknowledge the European Commission for financial support received under the Adriatic-Ionian Programme INTERREG V-B Transnational 2014–2020. Project #118 – SUPER-LNG “SUstainability PERformance of LNG-based maritime mobility”.

References (71)

  • T. Iannaccone et al.

    Inherent safety assessment of alternative technologies for LNG ships bunkering

    Ocean Eng.

    (2019)
  • S. Jafarzadeh et al.

    LNG-fuelled fishing vessels: a systems engineering approach

    Transport. Res. Transport Environ.

    (2017)
  • B. Jeong et al.

    An effective framework for life cycle and cost assessment for marine vessels aiming to select optimal propulsion systems

    J. Clean. Prod.

    (2018)
  • B. Jeong et al.

    Investigation on marine LNG propulsion systems for LNG carriers through an enhanced hybrid decision making model

    J. Clean. Prod.

    (2019)
  • N. Khakzad et al.

    Cost-effective fire protection of chemical plants against domino effects

    Reliab. Eng. Syst. Saf.

    (2018)
  • G.A. Livanos et al.

    Techno-economic investigation of alternative propulsion plants for Ferries and RoRo ships

    Energy Convers. Manag.

    (2014)
  • D.S. Mallapragada et al.

    Life cycle greenhouse gas emissions and freshwater consumption of liquefied Marcellus shale gas used for international power generation

    J. Clean. Prod.

    (2018)
  • A. Maragkogianni et al.

    Evaluating the social cost of cruise ships air emissions in major ports of Greece

    Transport. Res. Transport Environ.

    (2015)
  • R.A.O. Nunes et al.

    The activity-based methodology to assess ship emissions - a review

    Environ. Pollut.

    (2017)
  • J. Ren et al.

    Measuring the sustainability of marine fuels: a fuzzy group multi-criteria decision making approach

    Transport. Res. Transport Environ.

    (2017)
  • J. Ren et al.

    Selection of sustainable alternative energy source for shipping: multi-criteria decision making under incomplete information

    Renew. Sustain. Energy Rev.

    (2017)
  • E. Santoyo-Castelazo et al.

    Sustainability assessment of energy systems: integrating environmental, economic and social aspects

    J. Clean. Prod.

    (2014)
  • O. Schinas et al.

    Feasibility and commercial considerations of LNG-fueled ships

    Ocean Eng.

    (2016)
  • S. Stoumpos et al.

    Marine dual fuel engine modelling and parametric investigation of engine settings effect on performance-emissions trade-offs

    Ocean Eng.

    (2018)
  • H. Thomson et al.

    Natural gas as a marine fuel

    Energy Pol.

    (2015)
  • N.L. Trivyza et al.

    A novel multi-objective decision support method for ship energy systems synthesis to enhance sustainability

    Energy Convers. Manag.

    (2018)
  • A. Tugnoli et al.

    Sustainability assessment of hydrogen production by steam reforming

    Int. J. Hydrogen Energy

    (2008)
  • E. Tzannatos

    Ship emissions and their externalities for the port of Piraeus - Greece

    Atmos. Environ.

    (2010)
  • Y. Yan et al.

    Multi-objective design optimization of combined cooling, heating and power system for cruise ship application

    J. Clean. Prod.

    (2019)
  • S. Zhang et al.

    An alternative benchmarking tool for operational energy efficiency of ships and its policy implications

    J. Clean. Prod.

    (2019)
  • M. Anderson et al.

    Particle- and gaseous emissions from an LNG powered ship

    Environ. Sci. Technol.

    (2015)
  • A.A. Banawan et al.

    Environmental and economical benefits of changing from marine diesel oil to natural-gas fuel for short-voyage high-power passenger ships

    Proc. Inst. Mech. Eng. Part M J. Eng. Marit. Environ.

    (2009)
  • J. Bare et al.

    Development of the method and U.S. Normalization database for life cycle impact assessment and sustainability metrics

    Environ. Sci. Technol.

    (2006)
  • D. Baresic et al.

    LNG as a Marine Fuel in the EU: Market, Bunkering Infrastructure Investments and Risks in the Context of GHG Reductions. London

    (2018)
  • Bunker Index

    Europe regional bunker prices

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