Restrictions imposed by IMO (International Maritime Organization) on the content of sulfur oxides in the ship's fuel are inevitably approaching. It is obvious that the transition from high sulfur fuel oil (3.5%) to the distillate (0.5% sulfur content) will not be one-stage around the world, and certainly will add work for seafarers.
However, it is too late to make amendments (changes are possible only through the MARPOL VI); and Edmund Hughes, Head of Air Pollution and the IMO Energy Efficiency, believes that 96% of the vessels, mostly larger vessels will comply with the new requirements already January 1, 2020.
Some shipowners, who install scrubbers on ships, will continue to use high-sulfur fuel oil; some will switch to fuel oil with low sulfur content to meet the requirements. Meanwhile, there is a third way. We have prepared an overview of the alternative types of marine fuel that can replace the traditional oil. They have almost no SOx and can significantly reduce emissions of other greenhouse gases.
LNG - fuel for ships
Scrubbers lead in the preparatory technology race to the IMO Sulphur Cap 2020, and already in October 2019, 3023 vessels were equipped with scrubbers or have ordered installation. However, in the league of alternative fuels liquefied natural gas is in the first place. As of February 2019 there were 143 vessels in the world, running on LNG, and a further 135 were under construction.
The use of the liquefied natural gas in the ship's engine requires a moderate amount of modifications. However, there is a number of advantages and disadvantages of the LNG propulsion system:
Pros of LNG fuel
- Liquefied natural gas is the cleanest fuel, because it produces the least amount of GHG (greenhouse gas).
- LNG is used as fuel for ships since the early 2000s, so the technology is already developed, and there are many suppliers of the market. Competition also drives prices down .
- In addition, the cost of LNG is comparable to the price of traditional fuel. Liquefied natural gas is not yet able to compete with masut because of logistics, and other expenses; however, unlike other alternative fuels, LNG will become a complete substitute for oil in the near future. According to experts, the share of LNG will reach 23% in the total volume of marine fuel in 2050 (it is now about 0.3%).
- Piston engines, gas turbines and supplies to them, as well as special cryogenic fuel systems are commercially available and are freely available for LNG.
Cons of LNG fuel:
- LNG has a higher energy density compared with fuel oil, but the energy content per unit volume is only 43% of the high sulfur fuel oil. Therefore, fuel tanks take up to 3-4 times more space compared to vessels operating on the traditional fuel.
- Problems in bunkering. General reluctance to introduce LNG-fueled engines in shipping industry was partly due to the logistical difficulties. Liquefied natural gas for the marine engines isstill to be found only in a limited number of ports around the world, and this does not suit the majority of players. Often the ships have long routes, not defined in advance where the next point is, and therefore, the fuel must be available at any port. So often companies take a wait for new technologies.
Methanol - a promising marine fuel
Waterfront Shipping Company recently celebrated the addition in the fleet - two ships for the transportation of methanol working on two types of fuel. Mari Couva and Mari Kokako have 49,000 tons deadweight, and will use diesel and methanol, testing its ability as ship fuel.
In fact, CH3OH (methanol) is second in the ranking after LNG promising alternative fuels. In addition, this gas has advantages that make it more convenient for use in the marine industry:
- Methanol is liquid at a temperature of from -93 C to + 65 C (at atmospheric pressure), which eliminates the need for complicated confinement systems, cryogenic (cost fuel system using methanol, is about 1/3 of the price of the system for LNG ship engine).
- It can be produced from natural gas, coal and renewable sources. There are technologies that produce methanol directly from harmful emissions, and it appears most promising in view of COx emissions.
- NOx emissions depend on the type of engine. In the case of two-stroke diesel engine, a reduction in emissions will be 30% (compared to the high sulfur fuel oil), while the use of a four-stroke engine will reduce emissions by 60%.
Ammonia - new fuel for ships
The Dutch C-Job Naval Architects company recently proposed concept tanker carrying ammonia which uses its own cargo as fuel. Their research showed that NH3 may be another option of an alternative marine fuel in the case of the adoption of certain security measures. Key findings are as follows:
- Solid-oxide fuel cells are the most efficient power generation technology for ammonia fuel, but there are some practical problems (low specific power output, the engine response to load), and the high cost of the system, which prevents its conversion into a working model.
- Ammonia fuel does not contain a carbon component, therefore, does not emit COx. At the same time, the NOx emissions are kept at a reasonable level, so it is a reasonable choice in terms of environmental protection.
- Safe handling of ammonia on board ships, not intended for the transport of NH3 goods, require installation of complex and expensive protective equipment (detectors, shut-off valves for isolating leaks, fuel systems with double walls, t. D.)
- At the same time, ammonia fuel there will be no problems with bunkering, since it is produced throughout the world and is transported through the majority of ports.
Ships on hydrogen fuel
H2 - another interesting option of an alternative marine fuel, which is currently under consideration. For use on ships, liquefied hydrogen (cryogenic fluid has a temperature of -240 ° C) is placed in compression tanks, or stored as a chemical compound.
Currently H2 is produced from natural gas, as well as by electrolysis. The latter can be carried out on solar and wind power together with power generation. Produced from renewable sources of energy, hydrogen has become one of the most clean fuel with zero emissions of greenhouse gases.
The most effective energy generator for H2 are fuel cells. Production of hydrogen and fuel cells is well developed, but they still remain uncompetitive on price with conventional marine engines.
Meanwhile, the port of Antwerp has ordered «Hydrotug», the first tug working on H2. They found a compromise so the tug will use hydrogen and capabilities of the internal combustion engine. Hydrotug will boast ultra-low emissions, since it combines 2-fuel technology and sophisticated particle filter.
The tug will be built by Compagnie Maritime Belge (CMB) in two years.
Biofuels
Have you ever wondered what the vessels can use biodiesel or biogas as a fuel? Marine Engineers in Norway and Netherlands have developed concepts working on biofuel from hydroprocessed vegetable oil, fatty acid methyl ester (FAME) or liquefied biogas. This is mainly passenger ships, ferries, offshore and specialized vessels.
The main component of bio-fuel is methane, so its behavior is very similar to the use of LNG or methanol. However, biofuel production is now much more expensive.
The scientists also foresee some problems with the bunkering. Today, biofuels are only available in certain ports of Norway, Netherlands, USA and Australia. Thus, these projects are developed at the local level, but biofuel is already included in the DNV GL evaluation of alternative fuels. It has been studied extensively and is seen as a real option of an alternative marine fuel for future vehicles.
