Reduction in greenhouse gas and other emissions from ship engines: Current trends and future options

Päivi T. Aakko-Saksa (Corresponding Author), Kati Lehtoranta, Niina Kuittinen, Anssi Järvinen, Jukka Pekka Jalkanen, Kent Johnson, Heejung Jung, Leonidas Ntziachristos, Stéphanie Gagné, Chiori Takahashi, Panu Karjalainen, Topi Rönkkö, Hilkka Timonen

Research output: Contribution to journalReview Articlepeer-review

35 Citations (Scopus)
253 Downloads (Pure)


The impact of ship emission reductions can be maximised by considering climate, health and environmental effects simultaneously and using solutions fitting into existing marine engines and infrastructure. Several options available enable selecting optimum solutions for different ships, routes and regions. Carbon-neutral fuels, including low-carbon and carbon-negative fuels, from biogenic or non-biogenic origin (biomass, waste, renewable hydrogen) could resemble current marine fuels (diesel-type, methane and methanol). The carbon-neutrality of fuels depends on their Well-to-Wake (WtW) emissions of greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4), and nitrous oxide emissions (N2O). Additionally, non-gaseous black carbon (BC) emissions have high global warming potential (GWP). Exhaust emissions which are harmful to health or the environment need to be equally removed using emission control achieved by fuel, engine or exhaust aftertreatment technologies. Harmful emission species include nitrogen oxides (NOx), sulphur oxides (SOx), ammonia (NH3), formaldehyde, particle mass (PM) and number emissions (PN). Particles may carry polyaromatic hydrocarbons (PAHs) and heavy metals, which cause serious adverse health issues. Carbon-neutral fuels are typically sulphur-free enabling negligible SOx emissions and efficient exhaust aftertreatment technologies, such as particle filtration. The combinations of carbon-neutral drop-in fuels and efficient emission control technologies would enable (near-)zero-emission shipping and these could be adaptable in the short- to mid-term. Substantial savings in external costs on society caused by ship emissions give arguments for regulations, policies and investments needed to support this development.

Original languageEnglish
Article number101055
JournalProgress in Energy and Combustion Science
Publication statusPublished - Jan 2023
MoE publication typeA2 Review article in a scientific journal


  • Ammonia
  • BC
  • Black carbon
  • Carbon-neutral fuels
  • CH
  • Climate
  • CO
  • Emission control
  • Environment
  • Exhaust
  • Exhaust aftertreatment
  • External costs
  • Formaldehyde
  • Greenhouse gases
  • Health
  • Heavy metals
  • Marine engines
  • Methane
  • NO
  • NH
  • PAHs
  • Particle number
  • Particulate matter
  • PM
  • PN
  • SO
  • Warming


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