{"id":94531,"date":"2022-06-15T12:00:00","date_gmt":"2022-06-15T10:00:00","guid":{"rendered":"https:\/\/industry-science.com\/?post_type=article&p=94531"},"modified":"2024-04-11T16:09:47","modified_gmt":"2024-04-11T14:09:47","slug":"green-fuels-in-maritime-shipping","status":"publish","type":"article","link":"https:\/\/industry-science.com\/en\/articles\/green-fuels-in-maritime-shipping\/","title":{"rendered":"Green Fuels in Maritime Shipping"},"content":{"rendered":"\r\n

Roughly 2.5% (940 million tons of CO2<\/sub> per year) of global CO2<\/sub> emissions are emitted by the maritime transportation sector [1]. This number is higher than the total CO2<\/sub> emissions of Germany (739 million tons in 2020) [2]. In an effort to stabilize and reduce global warming, many national and international measures limit the use of conventional fuels.<\/p>\r\n\r\n\r\n\r\n

The International Maritime Organization (IMO) Green House Gas Strategy targets a 50% reduction of CO2<\/sub> emissions by 2050, taking 2008 values as a baseline, and aims to reduce this to 0% as soon as possible [3]. In November 2021, the International Chamber of Shipping (ICS) declared its intention to IMO of climate neutrality by 2050. Additionally, worldwide limitations on sulfur dioxide emissions for ships outside the emission control areas (ECAs) were reduced from 3.5% to 0.5 % as of January 2020 [4].<\/p>\r\n\r\n\r\n\r\n

Aside from CO2<\/sub> emissions, other air- polluting emissions like nitrogen oxide (NOX<\/sub>), sulfur oxide (SOX<\/sub>) and fine dust (particulate matter and soot) must be reduced. Many regulations, such as the IMO\u2019s TIER I and TIER II emission standards, apply to ships calling at offshore ports or terminals in international waters or using inland waterways. The SOX<\/sub> limit, which applies to SOX<\/sub> Emission Control Areas (SECAs) in the North Sea, Baltic Sea, North American coast and US Caribbean, has been 0.1% since 2015. NOX<\/sub> emissions must be reduced by 80% as per the TIER I directive in the NECA (NOX<\/sub> Emission Control Areas). The NECA also applies to the North Sea, Baltic Sea, North American coast, and the US Caribbean.<\/p>\r\n\r\n\r\n\r\n

These regulations bring the air-polluting emissions generated by the cruise industry into public focus. The cruise industry can work towards a greener public image by implementing emission-reducing technologies and environment friendly green fuels.<\/p>\r\n\r\n\r\n\r\n

An initial step of combining of fuel types and usage of aftertreatment technologies can go a long way towards emission reduction. But the energy used to produce ship fuels also has a large impact on emission (from well to wheel). In the following sections, this article compares fuel types, production chains and cleaning technologies, particularly with regards to their levels of air-polluting emissions. Future fuel prices for conventional ship fuels could steeply increase due to price increases for CO2<\/sub> emissions and limitations in oil production.<\/p>\r\n\r\n\r\n\r\n

\"Green\r\n
Figure 1: Air-polluting emission levels for a) nitrogen oxide (NOX<\/sub>), b) sulfur oxide (SOX<\/sub>), c) fine dust (PM), and d) carbon dioxide (CO2<\/sub>) for various fuel types and treatment technologies. <\/em> Legend: HFO = Heavy Fuel Oil, MDO = Marine Diesel Oil, LNG = Liquefied Natural Gas, SCR = Selective Catalytic Reaction. Data source [5].<\/em><\/figcaption>\r\n<\/figure>\r\n\r\n\r\n\r\n

State-of-the-art technologies for emission reductions<\/h2>\r\n\r\n\r\n\r\n

Air-polluting emissions like nitrogen oxide (NOX<\/sub>), sulfur oxide (SOX<\/sub>), fine dust (particulate matter and soot) could be reduced with a two-part technological approach. Scrubber technology ensures reduction of fine dust, particulate matter and sulfur dioxide, while SCR (selective catalytic reduction) technology is employed to reduce nitrogen oxide emissions.<\/p>\r\n\r\n\r\n\r\n

Figure 1 shows the levels of air-polluting gases present when a variety of fuel types and treatment technologies are used. The control scenario, which displays a 100% value, uses HFO (heavy fuel oil) without any treatment technology.<\/p>\r\n\r\n\r\n\r\n

The emission reduction achieved depends on the production chain, e.g. conventional LNG vs. green LNG. Ammonia, like hydrogen, is defined as a green fuel if the production chain utilizes green electrical energy. Additionally, ammonia is considered a green fuel when obtained as an industrial byproduct.<\/p>\r\n\r\n\r\n\r\n

The NOX<\/sub> emissions of HFO or Marine Diesel Oil (MDO) in fuels which are combined with treating technologies (Figure 1a) show no difference compared to conventional LNG. It is also clear that green LNG and green methanol do little to reduce NOX<\/sub> emissions. Only use of green hydrogen fuel reduces NOX<\/sub> emissions to zero.<\/p>\r\n\r\n\r\n\r\n

The sulfur oxide emissions (Figure 1b) can be reduced to ca. 20% of the control scenario value by using conventional fuels with treatment technologies. SOX<\/sub> emissions can also be significantly reduced by using green fuels.<\/p>\r\n\r\n\r\n\r\n

In Figure 1c, the particulate matter (PM) can be nearly eliminated by utilizing Scrubber technology in MDO or HFO. For particulate matter, the additional advantage offered by applying green fuels on top of treatment technology is very low, as it only reduces PM levels by a further 3 percent.<\/p>\r\n\r\n\r\n\r\n

Applying treating technologies (Scrubber and SCR) to conventional fuels does not reduce carbon dioxide (CO2<\/sub>) emissions (Figure 1d). Conventional hydrogen, which is based on fossil coal and natural gas, offers a CO2<\/sub> reduction potential under 25%. However, green methanol, green ammonia and green hydrogen all enable significant CO2<\/sub> reduction. The fuel production chain (well to wheel) is a key factor that influences the CO2<\/sub> emissions and can be an obstacle to their reduction. In addition, it is crucial to remember that use of LNG or other methane fuels in combustion engines can result in a methane slip. The methane slip can be up to 2% in dual fuel engines. The impact of methane on global warming is 25 times higher than that of carbon dioxide. Methane slip can be eliminated by a high-temperature or catalytic exhaust treatment.<\/p>\r\n\r\n\r\n\r\n

General outcome of the fuel type comparison: In order to operate in a \u201cgreen and clean\u201d way, the cruise and general maritime industry must adopt green fuels.<\/p>\r\n\r\n\r\n\r\n

\"Green\r\n
Figure 2: Specific ship engine power by weight (kW\/ Gt) and potential energy consumption reduction (%) for selected cruise ships. Data source [5].<\/em><\/figcaption>\r\n<\/figure>\r\n\r\n\r\n\r\n

Highly efficient technologies<\/h2>\r\n\r\n\r\n\r\n

By increasing the overall efficiency of an element, e.g. the propulsion drive of a cruise ship, the energy consumption specific to that element can also be reduced. Figure 2 shows the specific ship engine power of a selection of cruise ships by weight (kW\/Gt).<\/p>\r\n\r\n\r\n\r\n

The cruise ship Radiance of the Seas serves as the benchmark or baseline with 0.44 kW\/Gt. Over 17 years, the installed specific power was reduced by -55% to 0.20 kW\/Gt on the ship AiDAnova. Also, the time needed to increase efficiency rapidly decreases from 7 years to 4 years.<\/p>\r\n\r\n\r\n\r\n

Physical laws and technologies limit the increase of efficiency. Modern passenger ships already have energy-saving electric components installed, meaning there is limited potential to further decrease energy consumption by reinstalling new equipment.<\/p>\r\n\r\n\r\n\r\n

On the one hand, if energy efficiency increases, the specific amount of energy needed decreases. On the other hand, bigger ship sizes and a growing number of ships worldwide increases the total energy consumption of the cruise industry. This phenomenon is known as the rebound effect. Therefore, further increases in efficiency or reductions in energy consumption cannot be expected. Employing new technologies can nonetheless optimize the overall emission levels of a ship\u2019s energy supply systems.<\/p>\r\n\r\n\r\n\r\n

General outcome of energy efficiency technologies: Energy efficient technologies reduce CO2<\/sub> emissions, but do not eliminate them entirely.<\/p>\r\n\r\n\r\n\r\n

Green fuel production chain<\/h2>\r\n\r\n\r\n\r\n

Electrical energy can support the mobility or transport sector with power lines, batteries, hybrid systems or green fuels. For the maritime sector, hybrid systems (system combination e. g., green fuels and batteries) or green fuels are most practical due to the weight and distances involved.<\/p>\r\n\r\n\r\n\r\n

Figure 3 shows the green fuel production chain. Due to conversions steps, e.g. from electrical energy to hydrogen, 30%-40% of the energy is lost. Renewable electrical energy (wind or photovoltaic) is transferred to other energy forms like green hydrogen, green SNG (Synthetic Natural Gas), green LNG (Liquefied Natural Gas) or green methanol. Green ammonia (NH3<\/sub>) could be also used as a future green fuel for maritime sector.<\/p>\r\n\r\n\r\n\r\n

\"Green\r\n
Figure 3: Green fuel production chain based on renewable electrical energies e. g. wind, being fed into an electrolyser, followed by different synthesis steps and resulting in methanol as the final product [6].<\/em><\/figcaption>\r\n<\/figure>\r\n\r\n\r\n\r\n

Green hydrogen could thus be delivered to end consumers, i.e. ships. Otherwise, green hydrogen could be transformed into green fuels like methanol or SNG with CO2<\/sub> through different synthesis steps. Green SNG is the basis for green LNG. Green CO2<\/sub> could be extracted from biogas plants or in the future captured from air.<\/p>\r\n\r\n\r\n\r\n

Storage problems for green fuels<\/h2>\r\n\r\n\r\n\r\n

Bunkering green fuels effectively is a task that will play a role in the future of industry. The energy density (gravimetric and volumetric) of liquid or gaseous fuels plays an important role.<\/p>\r\n\r\n\r\n\r\n

In Figure 4, standardized energy densities (gravimetric: MJ\/kg and volumetric: MJ\/m3<\/sup>) of different fuel types are shown, using diesel as a benchmark. High energy density is reached with diesel. This sort of energy density is needed for long-distance travel and big propulsion drive systems with a high energy consumption.<\/p>\r\n\r\n\r\n\r\n

\"Green\r\n
Figure 4: Standardized energy densities (gravimetric: MJ\/kg and volumetric: MJ\/m3<\/sup>) of different fuel types, with diesel as a benchmark.<\/em><\/figcaption>\r\n<\/figure>\r\n\r\n\r\n\r\n
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Explanation of Figure 4:<\/strong><\/h4>\r\n\r\n\r\n\r\n