Alternative Sources of Power
Maritime transport has traditionally relied on the use of conventional fossil fuels. However, regulatory developments aiming to reduce air emissions, including air pollutants, and the need to contribute to greenhouse gas reductions have led to an increased focus on low-sulphur or -emission technologies, alternative or low-carbon fuels and other sustainable fuel and energy-efficient technologies.
This page gives an overview of some of the emerging alternative fuel technologies that are either being used or are being investigated for further use in the maritime industry.
The use of liquefied natural gas (LNG) as ship fuel can substantially reduce the release of air pollutants like sulphur oxide (SOx; a reduction of up to 90%), particulate matter (PM; a reduction of up to 90%) and nitrogen oxides (NOx; a reduction of up to 80%) compared to traditional fossil fuels. In 2020, a total of 59 ports in the EU had LNG installations, totalling 71 facilities.
Biofuels are fuels that are derived from feedstock resources such as oil and sugar crops, forest or agricultural residues or algae (i.e. biomass). These feedstocks undergo several processes before being converted into a biofuel.
Of the various biofuels, biodiesel can be used as a substitute for MGOs, marine diesel oils and other marine fuel oils in low- to medium-speed diesel engines, which are normally installed on tugboats, small carriers or cargo ships. However, they are currently more commonly used as a fuel additive and are poured directly (drop-in) into blended fuels.
The use of biodiesels (i.e. fatty acid methyl ester or FAME) in automotive diesel engines has been shown to reduce SOx, carbon monoxide and unburned PM emissions. Second-generation biofuels, such as hydrotreated vegetable oils (HVOs), are growing in importance in the maritime fuel mix.
Hydrogen (H2) as an alternative fuel can be used on board ships using two separate energy conversion technologies: fuel cells or in internal combustion engines.
In fuel cells, H2 is combined with oxygen in a process that is the reverse of electrolysis. As a result of the exothermic electrochemical reaction, both heat and water are by-products of electricity generation. No air pollutant emissions are formed during this process.
In an internal combustion engine, H2 can be burned in the presence of air in the same way as traditional fuel oils or LNG, but in this case the combustion will produce NOx as one part of the exhaust gas stream.
Ammonia (NH3) has the potential to be used as an alternative fuel on ships based on its physical and chemical properties. Its widespread use in industrial and agricultural processes may also facilitate its distribution using the existing infrastructure and supply chains.
On board ships, NH3 can be used in combination with internal combustion engines and fuel cells. In combination with internal combustion engines, its expected performance is similar to that of conventional fuels in relation to power density and load response. However, due to its toxicity and more stringent storage and handling requirements, NH3 engines are still at the development stage.
Fuel cells are an energy conversion system, not a fuel per se. They transform the electrochemical potential energy of hydrogen (H2) into electrical energy, which is then either consumed directly or, as in most cases, indirectly stored in batteries.
Fuel cells are primarily H2 consumers. Several technical arrangements exist whereby different fuels are directly fed into the fuel cells, such as LNG or methanol, which are used as chemical carriers/sources of the H2.
However, as the safety provisions for the use of fuel cells in shipping are still under development, the current deployment of fuel cells in the maritime transport sector is still limited.
EMSA has carried out a number of studies related to alternative fuels, including a study on LNG, a study on biofuels, a study on the use of fuel cells in shipping, and a study on the use of ethyl and methyl alcohol as alternative fuels in shipping. Further studies are underway including on the use of ammonia and hydrogen.
EMSA also provides support to the European Commission, through technical assistance and data, on the FuelEU Maritime Initiative.