Options for CO2 cutting fuels

Reducing CO2 from vessel operations through performance improvements only gets you so far on CO2 – in due course, shipping companies will need to consider options for different fuels. ABS considers three options - light gas (LNG / hydrogen), heavier (LPG / methanol), and liquids (bio/synthetics)

By Georgios Plevrakis, Director of Global Sustainability, ABS


The shipping industry is being challenged daily by the need to improve its environmental performance and reduce its contribution to climate change.

The debate is welcome, but the result is often a welter of competing voices discussing solutions that are still far from commercial availability.

Rather less attention is paid to what owners can do in the shorter term to begin to manage the transition to a carbon neutral future.

This confusion is more than theoretical; a situation in which owners weigh their options for the future risks a slowdown in newbuildings at a time when new orders are already close to historical lows.

Although the IMO will announce its final decision for the implementation of the 2030 and 2050 carbon reduction deadlines by 2023, there are several facts that are already known.

There will be no ‘cheap fuel’ in future. The IMO 2020 regulation has begun this process, but the industry needs to accept that carbon neutral and zero carbon fuels could be two to three times more expensive than those currently used.

The technical developments for producing the fuels that shipping needs are still in progress, however, the industry has some options to begin reducing carbon. Choices which fall into pathways that will ultimately bring them to sustainability.

The vessel type and trade pattern will play a significant role in determining the choice of pathway to sustainability; different fuels suit different vessel applications, whether large or small, coastal or deepsea.

As such ABS is fuel and technology agnostic; we are working with owners and shipyards to identify the right path for their specific vessels and business case to deliver safe, practical, and simple solutions.


Three pathways

ABS has identified three fuel pathways potentially open to shipping.

The first can be defined as ‘LNG or light gas’, using generally light, small molecule fuels with high energy content, but more demanding, mainly cryogenic fuel supply systems and storage. This group includes the relatively mature methane (as LNG) solution leading towards bioderived or synthetic methane, and ultimately to hydrogen as fuel.

On this pathway, if methane slip is discounted [methane which slips through the engine without combusting], LNG can reduce CO2 emissions by 20 per cent. Bio-methane can be carbon neutral, while hydrogen is a zero carbon fuel.

Methane slip is starting to receive detailed scrutiny and though is not at present subject to regulation, this is expected to change in the near future.

As a result, there is intense industry focus on minimizing methane slip. Whether this can be achieved in the context of potential regulatory changes could be a defining factor for the future of LNG as fuel.

Hydrogen can serve as the ultimate solution along this pathway, but it will necessitate significant technical advances, which may require a decade or more, until it becomes a practical solution. Although hydrogen has lower volumetric energy density than methane, it has far higher energy content, almost three times that of LNG and HFO.

The second pathway is defined as ‘LPG/ Methanol’, by using generally heavier, more complex molecules with lower energy content, but with less demanding fuel supply and storage requirements than the light gas pathway. This group includes LPG, methanol and ethanol, leading to bio-derived or synthetic LPG/methano and ultimately to ammonia.

The fact that most of these fuels have a lower energy content imposes constraints on the types of vessels, trades, and routes they can be used on but in their first generation are already mature.

LPG and methanol are parts of the existing technology mix. On this pathway, methanol can reduce CO2 by 10 per cent, while bio-methanol can be carbon neutral, and ammonia is a zero carbon fuel.

While ammonia shows considerable promise as a fuel, the technology for its storage and application still needs to be developed, and regulations must account for its particular safety considerations.

The third pathway hinges on bio/synthetic fuels that are derived from renewable sources and can produce liquid fuels.

These fuels have similar properties to diesel oil and thus are much less demanding in terms of new infrastructure and technologies onboard and can be utilized with minimal changes to current ship designs.

Currently, the most widely used bio-derived fuel is biodiesel (also known as FAME). The use of FAME is included in the latest ISO 8217/2017 fuel specification for marine fuel blends, which allows for 7 per cent biodiesel by volume, though some owners are known to be testing richer blends with up to 20 per cent or higher.

First generation, plant-derived biofuels face challenges such as competition with food crops and high carbon intensity during production, but second generation biofuels, such as hydro treated vegetable oil (HVO), can overcome these challenges while offering similar energy content to MGO.

In the future, a third generation of biofuels, such as lignocellulosic or algae-based fuels could potentially provide the industry with almost 500 million tons of fuels annually, more than the current annual bunker demand. This group includes electro/synthetic Gas-to-Liquid (GTL) fuels produced though either carbon capture and electrolysis, or from converting biomass to syngas and then to liquid fuels such as methanol or diesel.

The main challenge in gas to liquid production is to make it economically attractive. If so, it can produce higher grades of hydrocarbon fuels which can be readily used in the engine, thus requiring the lowest capital investments for the ship of any of the three pathways.

Short term actions

The selection of the most appropriate fuel pathway and related technology is certainly a challenge, which includes considerations of the vessel’s size and design, as well as evaluation of whether lower or higher energy content fuels will best match its operational profile.

For owners considering vessel orders in the next five years, the choice is effectively between LNG, methanol and LPG since these will provide a pathway to carbon neutral and ultimately zero carbon fuels. By 2030, owners can expect that the options of carbon neutral fuels will be sufficient to provide them with the required blending capacity.

However, owners can take some steps to future-proof their vessels, starting with designs that assume the greater use of electrical propulsion to reduce the fuel consumption of the vessels. This philosophy assumes that the electricity can be produced from any fuel pathway and can be used for propulsion or power generation onboard, using batteries or fuel cells for full or partial load operation.

Forward-looking owners and charterers are already starting to look at electrical installations, whether to optimize the prime mover or for more efficient generators to minimize the carbon footprint of the vessels. It is already possible to specify a portion of electrical propulsion or specify the layout of the engine room for future retrofitting. The technology is still evolving but evaluating how to use electrical drives that are agnostic of fuel supply can be an effective way to future proof a design.


Decarbonization is a significant challenge, arguably the biggest the industry has ever faced, but it must be addressed; shipowners should not be bystanders in this process and they cannot arrive at the decarbonization targets alone.

By studying future fuels and by considering the degree to which electrical propulsion systems and new energy efficiency technologies will play a role in future, the shipowners can best position themselves in the marketplace.
Our approach is to simplify this complex problem and enable shipowners to make informed decisions about the fuels and systems that are right for their assets and operation.

At ABS, we see our role as a continuum by supporting the industry in understanding the nature of this challenge, helping our members, clients, and other industry stakeholders to assess the emerging landscape and ultimately the regulations with which they must comply.

Most importantly the transition to an era of new fuels must be accomplished safely, with development, testing, and implementation of new fuels along with propulsion systems subject to the same analytical rigour as any previous or existing maritime technology.






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