Zero Carbon Cruising

Aida Cruises launched the AIDAnova in 2018. Built by the Meyer Werft shipyards, it was the world’s first cruise ship to run on liquefied natural gas (LNG) and, as such, illustrates the shipping industry’s commitment to reducing its carbon footprint. Although the road will be long, the trend is irreversible.

Historically shipping has used heavy fuel oil (HFO) for propulsion, which is a heavy fraction distilled from crude oil. As this so-called “bunker fuel” is made from petroleum refining residues, it contains compounds, in particular sulphur, which make it more polluting. The combustion of heavy fuel oils results in emissions of CO2, sulphur oxides (SOx), nitrogen oxides (NOx) and particulate matter. Maritime transport represented just under 3% of global CO2 emissions in 2018, the equivalent of Germany’s annual emissions.

The International Maritime Organization has decided to react and has set ambitious targets to curb greenhouse gas emissions (at least 50 % below 2008 levels by 2050). Since 2015, the IMO has also imposed a progressive reduction in the maximum permitted Sulphur content (from 3.5 % in 2015 to 0.5 % in 2020) in the bunker fuels of some 50,000 ships in circulation worldwide. In the Sulfur Emission Control Areas (SECA), which include the North American coasts and the seas of Northern Europe, even stricter limits apply with a maximum sulphur content of 0.1% as of 2015. Different solutions are available to shipowners to help them comply with requirements. The first consists in replacing heavy fuel oils with marine diesel or low Sulphur fuel oils, which requires some minor modifications to the ship’s engines to make them compatible. However this option involves significant additional operational costs (lowsulphur alternatives are much more expensive). Price and availability are key issues and the former will rise as demand increases, however this will initially be the most widely adopted solution as it does not require large investments.

Choose your weapons

Another avenue is to continue burning high sulphur fuels, but to reduce pollution levels by installing exhaust gas cleaning systems, also called “scrubbers”, which remove and collect sulphur. However this solution is not necessarily suitable for all ships. More importantly, it only eliminates sulphur emissions (and not NOx and other pollutants) and so it only addresses part of the problem. In terms of cost, this solution offers the best return on investment, but it is not without risk as it raises the question of how to dispose of the sulphur residues.

In addition, the carbon footprint of exhaust gas cleaning systems is disappointing; in fact operating this equipment increases the ship’s overall fuel consumption and therefore its greenhouse gas emissions. On 1 May 2019, less than 2,400 ships were equipped with exhaust gas cleaning systems.

The last option is to change over to an entirely new fuel, which for shipowners with a longterm strategy usually involves investing in a new vessel. Today, heavy fuel oils are being replaced by LNG and even, and we will come back to this later, by bio-LNG or hydrogen. As demonstrated by the AIDAnova, LNG is currently the most widely used new fuel source. Indeed, LNG complies with all environmental requirements as it has zero sulphur and particulate matter emissions, reduces NOx emissions by 80% and CO2 emissions by 20%. LNG is also available in large quantities and LNG engines for ships of various tonnages are available, however constraints exist because the logistics of LNG distribution are not adapted to this usage yet and the return on investment is also longer. With fewer than 400 ships powered by LNG in service or on order, this can still be considered to be a niche market, but some studies predict an annual potential for LNG-fuelled ships of 35 million tonnes by 2035, in other words a market share of approximately 10%.

In 2017, ENGIE joined forces with Mitsubishi, NYK line and Fluxys to launch the outfitting of the ENGIE Zeebrugge bunkering vessel. With a capacity of 5,000 m3, it will be able to supply LNG to ships of any type operating in Northern Europe from its base in the port of Zeebrugge (Belgium), which it will do from 2020 under the brand name “Gas4Sea”.

Better Than LNG

To address this new market, ENGIE has launched several ambitious research programmes that focus on the production of green gases and their use in the maritime transport sector. One of them addresses the fact that the thermodynamic behaviour of LNG is completely different to that of other fuels because LNG is a cryogenic liquid whose chemical composition changes as it evaporates into natural gas, which is then burned by the engines.

The changes that take place during the voyage are reflected in the evolution of parameters that are essential for the operation of the engines, including the methane number (a number linked to the composition of the gas that reflects combustion quality). A gas chromatograph could be installed to continuously monitor LNG composition, but such a device is expensive. Other solutions now exist: ENGIE Lab CRIGEN has developed Smart gauge, an algorithm that calculates the composition of the LNG in the ship’s storage tanks throughout the route based on real-time pressure and temperature measurements and the initial composition of the LNG.

Despite its low environmental impact, LNG does not completely eliminate CO2 and NOx emissions, however two new fuels could provide the solution. The first is bio-LNG (or liquid biomethane) i.e. liquefied biogas, which reduces CO2 emissions by 90% compared to heavy fuel oil and does not require any additional investment for LNG-powered ships. The development of bio-LNG is however hindered by its higher production costs. Building on more than 60 years’ experience in the field, ENGIE Lab CRIGEN has launched a research program aimed at using innovative processes to reduce the cost of the liquefaction of biogas by 40%. In 2020, tests will be carried out at the CRIGEN site in Stains and then at the LNG terminal in Montoir-de-Bretagne to validate the new technology. The objective for 2021 is to install the solution at the site of an ENGIE partner. Bio- LNG could replace LNG by 2030.

In the longer term, liquid hydrogen could be a suitable fuel source for maritime transport. In fact, as long as it is produced from renewable sources, it does not generate an greenhouse gases, nor does it emit NOx, Sox or particulate matter. Today available solutions for producing, storing and transporting liquid hydrogen are limited. ENGIE has launched a research program that aims to halve the costs of producing and transporting hydrogen by developing new liquefaction processes Projects are also underway in South America to provide industry with hydrogen-based maritime transport solutions.

Contrary to its reputation as a rather conservative industry, maritime transport is well on the way to becoming carbon neutral. Several solutions are available and ENGIE is supporting the key players to help them reduce the industry’s carbon footprint. 

One day soon, we will be able to cruise with a clear conscience.