Environmental assessment of alternative marine fuels and installations

Abstract

The rise in fossil fuel consumption has made global warming an inevitable outcome. Fossil fuels emit harmful air pollutants such as black carbon (BC), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), nitrogen oxide (NOX), organic carbon (OC), particulate matter (PM), sulfur oxide (SOX) and volatile organic compounds (VOCs). The primary contributors to climate change are greenhouse gases (GHGs), including CO2, CH4, and N2O. Besides, BC, OC, and VOC emissions have an impact on global warming. Moreover, acid rain, changes in the ecosystem, health issues, and alterations in ozone are the other effects of emissions. Stricter regulations have been introduced in land, aviation, and maritime transportation to limit the impacts of emissions. This thesis particularly focuses on the ship-based emissions side. Regulations have been adopted in the maritime sector for years under The International Convention for the Prevention of Pollution from Ships (MARPOL), but in the last decades, constrictor rules have been introduced. One of which is the NOX Technical Code adopted on 10 October 2008 to limit the NOX emissions produced by ship engines. Additionally, on 1 January 2013, new sets of rules were announced, namely the Energy Efficiency Design Index (EEDI) and Ship Energy Efficiency Management Plan (SEEMP), which are aimed at decreasing CO2 emissions. Moreover, on 1 July 2015, Monitoring, Reporting, and Verification (MRV) and on 1 March 2018, the Data Collection System (DCS) entered into force to mitigate CO2 pollutants. Besides, on 1 January 2020, a new sulfur limit was set for the ships sailing in the Emission Control Area (ECA) and outside ECA zones. Also, on 1 January 2023, the Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII) became effective, focusing on CO2 emission. In addition, a recent update on the GHG strategy of the International Maritime Organization (IMO) was made on 7 July 2023. The revision now targets a 20% reduction in GHG emissions by 2030, intending to reach 30%, and aims for a 70% decrease by 2040, striving for 80% compared to 2008 levels. Also, by 2050, total decarbonization is targeted. Moreover, on the same date, a Life Cycle Assessment (LCA) Guideline was announced to evaluate the emissions of marine fuels from a well-to-wake (WTW) perspective. Additionally, on 1 January 2024, a new regulation entered into force named the European Emission Trading Scheme (EU ETS). EU ETS is currently focusing solely on CO2 emission, but in the upcoming years, it will also involve other GHGs. Furthermore, on 1 January 2025, the FuelEU rule will be enforced to mitigate GHG emissions, and each five-year interval GHG intensity will be reduced. In order to comply with the regulations, various means of emission abatement measures have been proposed. While some of those measures involve modifications on a ship, some are operational solutions. For instance, slow-steaming, weather routing, ballast water operation, trim-draft optimization, autopilot improvement, smart propulsion control system, planned maintenance, hull-propeller cleaning, and artificial intelligence predictive maintenance are operational ways of mitigating ship-based emissions. On the other hand, pre-swirl stator propeller, propeller cap, propeller nozzle, propeller and rudder optimization, hull optimization, exhaust gas recirculation, water and steam injection, use of alternative fuel, engine and machinery modification, air lubrication system, hybrid power systems, fuel cells, electric ship, renewable energy, waste heat recovery system, shaft generator, carbon capture system, selective catalytic reduction system and sulfur scrubber are the measures require modifications on a vessel. Despite many emission abatement means being available, alternative fuels became a promising way to meet the limits enforced by the regulations. In the literature, many studies were conducted on alternative marine fuels, yet there are limited papers regarding the whole life cycle emissions of the fuels. Hence, this thesis study considered the WTW emissions of ammonia, biodiesel, dimethyl ether (DME), Electro Fischer-Tropsch Diesel (E-FT-Diesel), Electro-Methanol (E-Methanol), Fischer-Tropsch Diesel (FT-Diesel), hydrogen, liquefied natural gas (LNG), liquefied petroleum gas (LPG), marine bio-oil, methanol, pyrolysis oil, renewable diesel and straight vegetable oil (SVO). Furthermore, marine diesel oil (MDO), marine gas oil (MGO), and ultra-low sulfur fuel oil (ULSFO) are included in the study to enable a comparison chance with the currently utilized fuel choices. To investigate the WTW emissions of the fuels, the LCA method was employed. This analysis was conducted on a general cargo vessel equipped with a 2500 kW main engine and three auxiliary diesel engines, each with a power output of 220 kW. The WTW emissions were determined in two stages. At first, well-to-pump (WTP) results were obtained from the GREET Model 2023 software according to the assumptions made. In the second stage, pump-to-wake (PTW) emissions were calculated considering the voyage data received from the ship management company for the general cargo ship. Additionally, an Environmental Impact Assessment (EIA) was conducted using the OpenLCA program to evaluate the environmental impacts of the fuels. The EIA was carried out in nine different categories, which are acidification potential, climate change, freshwater ecotoxicity, marine eutrophication, terrestrial eutrophication, non-cancer human toxicity, particulate matter, photochemical oxidant formation, and photochemical ozone formation. Besides the LCA, a Life Cycle Cost Analysis (LCCA) was done to evaluate the fuels cost-wise. The LCCA involves Capital Expenditure (CapEx), life cycle fuel cost, and life cycle maintenance cost of each fuel and power installation. The LCA analysis reveals that in the acidification potential criterion, LNG is the prominent choice followed by DME. In the climate change environmental impact category, hydrogen, E-Methanol, and E-FT-Diesel are the superior options. In the freshwater ecotoxicity potential category, hydrogen is the dominant choice with a quiet margin. In marine eutrophication and terrestrial eutrophication, LNG is having a promising result, followed by DME. In the non-cancer human toxicity criterion, hydrogen once again emerges as the best fuel. Moreover, in the particulate matter impact category, LNG, LPG, and hydrogen have the lowest impact. In photochemical oxidant and ozone formation criteria, LNG prevails. The LCA results indicate that there is not a single fuel choice to mitigate the environmental impact of the fuels, but some of them have the potential to reduce overall environmental harm. LNG, DME, LPG, hydrogen, methanol, E-FT-Diesel, and E-Methanol are the most attractive options considering the LCA analysis. On the other hand, regarding the current trends of the regulations on GHG emissions, E-FT-Diesel, E-Methanol, hydrogen, and LPG have a lesser effect on climate change compared to MDO, considering the WTW results. In addition, LPG cannot meet the 2030 limits; thus, it can only benefit in the short term. Besides, hydrogen possesses the lowest impact on climate change, yet the NOX emission is an issue because of the NOX Technical Code. On the contrary, E-FT-Diesel and E-Methanol have better performance in each impact category with respect to MDO. The LCCA analysis shows the other essential point of the fuels. The primary contributor to the life cycle cost is the fuel cost, while maintenance and CapEx have similar impacts. According to the findings, MDO, ULSFO, and FT-Diesel have the lowest life cycle costs with $8.91M, $8.93M, and $9.43M, respectively. E-FT-Diesel, which is one of the prevailing fuels according to LCA, has the twelfth highest life cycle cost with $18.11M, while E-Methanol is the fifteenth with $32.81M. The difference between the E-FT-Diesel and E-Methanol is $14.70M, with a slightly lower environmental impact of E-Methanol. Therefore, E-FT-Diesel becomes the most cost-efficient fuel choice. When making a final decision, other important aspects include the ship type, age, and sailing region. For instance, for cruise and roll-on-roll-off (Ro-Ro) ships, safety gains importance, while for cargo ships, the amount of carried cargo is essential. In addition, younger vessels will have to comply with upcoming regulations and thus are required to utilize cleaner fuels, while investments in older ships need to be lower. Furthermore, vessels sailing in less developed areas may have issues related to infrastructure and scarcity of fuel. Considering those, E-FT-Diesel, E-Methanol, LNG, LPG, and methanol can provide the desired conditions for the vessels.