The global merchant fleet currently consumes around 330 million tonnes of fuel annually, 80-85 per cent of which is residual fuel with high sulfur content. Shipping must change, and we must contribute technical measures, operational measures and alternative fuels to meet the challenges we are tackling. While renewable energy, particularly solar and wind, may have some potential to mitigate carbon emissions, this is not seen as a viable large-scale alternative for commercial shipping.

—Christos Chryssakis, DNV GL senior researcher and position paper project manager

To date, the paper notes, the shipping industry has not acted decisively to realize its potential to reduce emissions via low carbon energy due to a number of reasons, include capital cost, patchwork regulations, lack of standards, lack of appropriate infrastructure and uncertainty regarding long-term availability of fuel.

That is, owners will not start using new fuels if infrastructure is not available, and energy providers will not finance expensive infrastructure without first securing customers. Breaking this deadlock will require a coordinated, industry- wide effort and the political will to invest in the development of new infrastructure.

—“Alternative Fuels for Shipping”

DNV GL is studying a number of alternative fuels or energy carriers that are already used or could be potentially used in shipping in the future. These fuels are: liquefied natural gas (LNG); liquefied petroleum gas (LPG); methanol and ethanol; di-methyl ether (DME); synthetic fuels (Fischer-Tropsch); biodiesel; biogas; use of electricity for charging batteries and cold ironing; hydrogen; and nuclear.

For each one of these fuels, DNV GL is collecting: physical and chemical characteristics; production, availability and cost: information on production methods, current production volumes and prices, infrastructure, and future forecast, where available; applications and current status: applications in the maritime and in other sectors, with an overview of technology including engines and storage tanks; safety considerations; and emissions and environmental considerations.

Over the next four decades, it is likely that the energy mix will be characterized by a high degree of diversification. LNG has the potential to become the fuel of choice for all shipping segments, provided the infrastructure is in place, while liquid biofuels could gradually also replace oil-based fuels. Electricity from the grid will most likely be used more and more to charge batteries for ship operations in ports, but also for propulsion. Renewable electricity could also be used to produce hydrogen, which in turn can be used to power fuel cells, providing auxiliary or propulsion power. If drastic reduction of GHG emissions is required and appropriate alternative fuels are not readily available, carbon capture systems could provide a radical solution for substantial reduction of CO₂.

—“Alternative Fuels for Shipping”

Broadly, in the long term, DNV GL expects short sea shipping to take advantage of locally produced fuels such as biogas, biodiesel, methanol, shoreside electricity and hydrogen. Deep sea shipping needs globally available fuels and so will tend towards LNG and biodiesel, if it becomes available. Nuclear energy suffers from public perception problems but may come to the fore sometimes in the future if it will be perceived as a safe alternative.

LNG. LNG as fuel eliminates SO_x emissions, significantly reduces NO_x and particulate matter, and also reduces GHG emissions—although not to the levels that would be required for addressing climate change.

There are currently around 40 LNG fueled ships (excluding LNG carriers) in operation worldwide, according to the paper, while another 40 new buildings are now confirmed. LNG bunkering for ships is currently only available in a number of places in Europe, Incheon (Korea) and Buenos Aires (Argentina) but the world’s bunkering grid is developing. The number of ships is increasing fast and infrastructure projects are planned or proposed along the main shipping lanes of the world.

Barriers include the increased demand for fuel tanks, leading to a decrease in payload capacity and the relatively high capital cost of the system installation.

LNG engines currently being produced cover a broad range of power outputs. Engine concepts include gas-only engines; dual fuel 4-stroke; and 2-stoke. Methane slip during combustion is practically eliminated in modern 2-stroke engines, and further reductions should be expected from 4-stroke engines.

DNV GL expects LNG uptake to grow quickly in the next 5 to 10 years, first on relatively small ships operating in areas with developed gas bunkering infrastructure, where LNG prices are competitive to HFO (heavy fuel oil) prices. They will then be followed by larger ocean-going vessels when bunkering infrastructure becomes available around the world.

Ship electrification and renewables. Ship electrification holds significant promise for more efficient use of energy. Renewable power production can be exploited to produce electricity to power ships at berth (cold ironing), and to charge batteries for fully electric and hybrid ships.

Enhancing the role of electricity on ships will contribute towards improved energy management and fuel efficiency on larger vessels. For example, shifting from AC to on board DC grids would allow engines to operate at variable speeds, helping to reduce energy losses. Additional benefits include power redundancy and noise and vibration reduction.

If renewable energy from the sun or wind is not readily available for electricity production on shore, conventional power plants can be used. In this case GHG and other pollutants will still be emitted, but they can be reduced through exhaust gas cleaning systems or carbon capture and storage. Alternatively, nuclear power on shore could be used for emissions-free electricity production, to be used for charging of batteries on board.

Energy storage devices are critical for the use of electricity for ship propulsion, while they are also important for optimization of the use of energy on board in hybrid ships.

DNV GL expects significant growth in hybrid ships, such as harbor tugs, offshore service vessels, and ferries after 2020. After 2030, improvements in energy storage technology will enable some degree of hybridization for most ships. For large, deep sea vessels, the hybrid architecture will be utilized for powering auxiliary systems, maneuvering and port operations to reduce local emissions when in populated areas.

Biofuels. Biofuels derived from waste have many benefits, but securing the necessary production volume is a challenge. The land required for production of 300 M tonnes of oil equivalent (TOE) biodiesel based on today’s (first- and second-generation biofuels) technology is slightly larger than 5% of the current agricultural land in the world.

Algae-based biofuels seem to be the most efficient and the process has the added benefit of consuming significant quantities of CO₂, but more work needs to be done to identify alga strains that would be suitable for efficient large scale production. Concerns related to long-term storage stability of biofuels on board ships, and issues with corrosion also need to be addressed.

Biofuels will have only limited penetration in the marine fuels market in the next decade, according to the paper. By 2030, biofuels will play a larger role, provided that significant quantities can be produced sustainably, and at an attractive price.

Hydrogen. Compressed hydrogen has a very low energy density by volume requiring six to seven times more space than HFO. Liquid hydrogen on the other hand, requires cryogenic storage at very low temperatures (-253 °C or 20K), associated with large energy losses, and very well insulated fuel tanks.

Although operational experiences have shown that fuel cell technology can perform well in a maritime environment, further R&D is necessary before fuel cells can be used to complement existing powering technologies for ships.

Challenges include high investment costs, the dimensions and weight of fuel cell installations, and their expected lifetime. Special consideration has to be given to storage of hydrogen on board ships, to ensure safe operations. Significant improvements in technology, accompanied by cost reductions are required if fuel cells are to become competitive for ships.

DNV GL sugests that fuel cells can become a part of the future power production on ships, and in the near future it might be possible to see successful niche applications for some specialized ships, particularly in combination with hybrid battery systems.

Other liquid or gaseous fuel options. A number of liquid fuels can be used in dual fuel engines, as substitute for oil. Some of the fuels that can be used are Liquefied Petroleum Gas (LPG), methanol, ethanol, and di-methyl ether (DME). Most of these fuels offer significant reductions of NO_x and PM emissions, while they are sulfur free and can be used for compliance with regulations.

Due to the limited availability of all these fuels, DNV GL does not expect them to penetrate deep sea shipping sectors in the near- to medium-term future. However, they can become important parts of the fuel mix in local markets.

Nuclear. To avoid the possibility of making weapons out of the nuclear material, nuclear-powered ships would need to run on low-enriched nuclear material. Nuclear power can be used for propulsion on very large ships, or on vessels that need to be self-supporting for longer periods at a time. The Russian ice-breaker fleet, operating in the northern sea route, is one example where nuclear power is fully adapted.

Several nuclear powered navy vessels are in operation today; however, very few nuclear-powered merchant ships have ever been built, and all without commercial success.

Given the public opposition to nuclear power in most countries, and fears related to potential consequences from accidents, it seems very unlikely that nuclear propulsion will be adopted in shipping within the next 10-20 years. Nuclear power generation on land will stay at today’s levels, mostly due to developments in China. This picture could change after 2030, provided that societal acceptance increases, and other efforts to reduce GHG’s do not prove as effective as desired.

—“Alternative Fuels for Shipping”

“Well-to-propeller.” An evaluation of “well-to-propeller” greenhouse emissions, rather than just shipboard potential to reduce emissions, demonstrates some major drawbacks for some of the options, as does an evaluation of potential availability. For example, the availability of land to grow biofuels is a significant barrier to its widespread use, with an area the size of Greece required to produce 50 million tonnes of biodiesel.

At present, LNG represents the first and most likely alternative fuel to be seen as a genuine replacement for HFO for ships built after 2020. The adoption of LNG will be driven by fuel price developments, technology, regulation, increased availability of gas and the development of the appropriate infrastructure. The introduction of batteries in ships for assisting propulsion and auxiliary power demands is also a promising low carbon energy source. Ship types involved in frequent transient operations (such as dynamic positioning, frequent maneuvering, etc.) can benefit most from the introduction of batteries through a hybrid configuration. Moreover, energy storage devices can be used in combination with waste heat recovery systems to optimize the use of energy on board. Cold ironing could become a standard procedure in many ports around the world.

The pace of development for other alternative fuels, particularly biofuels produced from locally available waste biomass, will accelerate, and may soon compliment LNG and oil-based fuels. Indeed, it is likely that a number of different biofuels could become available in different parts of the world after 2030. However, acceptance of biofuels in deep-sea transportation can only take place if these fuels can be produced in large volumes and at a competitive price around the world.

—“Alternative Fuels For Shipping”

Resources

• Christos Chryssakis, Océane Balland, Hans Anton Tvete, Andreas Brandsæter (2014) Position Paper 17-2014: Alternative Fuels For Shipping