The shipping industry and shipowners are facing challenges in reducing exhaust gas emissions while maintaining efficient fuel and energy consumption. In the maritime decarbonization process, the focus is on alternative marine fuels that have the potential to achieve sustainable and green shipping. However, their implementation process is not easy due to high cost, handling and storage complications, and availability issues. This research analyses additives in marine diesel fuels and their impact on the emission reduction process. The analysis focuses on a comparison between traditional additives and SulNOx marine additive, a fuel conditioner product that is relatively new to the maritime sector. The key benefits of SulNOx are emission reductions, an improved combustion process (more efficient combustion), lower fuel consumption, improved lubricity and reduced carbon deposits on cylinder liner and piston rings. A more efficient combustion process is achieved with the secondary atomization method due to the presence of glycol ether in the additive, which also reduces soot formation in the cylinder, resulting in reduced particulate matter emissions. In terms of economic aspects and energy efficiency, SulNOx’s fuel savings could improve the Carbon Intensity Indicator (CII) of a ship and could reduce EU ETS costs. The average fuel savings and CO2 reduction in metric tons per year are presented with a simple calculator, where users can gain insight into how much savings they may achieve when using SulNOx. Exhaust gas emissions standards in the maritime sector are becoming more stringent and difficult for the shipowners to meet them. Currently, the majority of ships are powered by marine diesel engines that use diesel fuel oils, due to their high efficiency. The products of combustion process in diesel engines are harmful gases such as carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM). Nowadays, there are many technologies to reduce exhaust emissions from diesel engines, but the most efficient solution is to replace diesel fuels with environmentally friendly alternative fuels. However, this transition is not easy to achieve due to the high costs of alternative fuels when compared with traditional diesel fuels, and it requires modification of engines and holding tanks for storage. Another solution that is becoming more popular is adding additives in marine fuels to achieve lower exhaust emissions and improved combustion process. The impact of using marine additives is the focus of this research, with the goal of evaluating their potential for emission reduction, fuel efficiency, and engine performance. Moreover, it is an introduction to a new ongoing project ‘Smart Emissions’- reduction of exhaust gas emissions and energy efficient optimisation of passenger ships. During this project, the SulNOx additive will be used on two diesel test engines and on an RO-Pax vessel to evaluate its potential in marine applications. Before testing, it is necessary to analyse scientific literature with a similar topic and compare it with SulNox tests. In the research 1, the biodegradable additives were tested on a Sulzer 6AL20/24 while using conventional diesel fuel with two mixtures of alcohol (ethyl, butyl) and demineralized water. Results showed the reduction of NOx by 7.5%, but no changes in CO2 emissions. Effects of environmentally friendly additives on exhaust gases and fuel consumption are analysed in the article 2. When additives (2% silver solution) were added to the MDO fuel, NOx decreased by 4%, CO by 28%, and CO2 by 4.6%, and fuel consumption decreased by around 3%. Similar research 3 was conducted on a 4-stroke diesel engine (6N21L Yanmar) while using RME25 marine fuel with fuel additives. The experiment resulted in NOx reduction by 1.4% to 4.3%, fuel consumption by 3.5% and SOx by 15.6 to 22.9%. Fuel additives oil-soluble Ca-based and Fe-based were used in the article 4 on a large two-stroke marine engine fueled by HFO. SulNOx fuel conditioner is a biodegradable and 100% organic additive that can be used with HFO, MDO, VLSFO and some biofuels. It has already been tested in the maritime sector on tankers, offshore vessels, chemical tankers and bulk carriers. When compared with traditional additives, it has some additional benefits such as improved lubricity properties 5 (17%), reduced soot formation and PM emission. A more efficient combustion process is achieved with the secondary atomization method, where water droplets from fuel in the combustion chamber vaporise before ignition and create micro-explosions that separate large fuel droplets, which usually are responsible for soot formation. The results with SulNOx have revealed the average reduction in fuel consumption by 5%, CO2 by 25%, PM by 96%, SOx by 65% and NOx by 14%, however, these results still require further testing, especially on passenger ships that sail in special restricted areas while using cleaner marine fuels. Another advantage of SulNOx is the small amount (dosage rate 1:2000 – 1 ml per 2 l of fuel) required for mixing with the fuel. These advantages and product availability are reasons why it was chosen for the project; however, there are still some uncertainties that will be tested during the experimental phase of the project, such as the period required to achieve the first results and the compatibility with fuel equipment and fuel injectors. The potential of marine fuel additives has been recognized in recent years as an alternative solution for reducing exhaust gas emissions. This research analyzed the usage of different fuel additives in the shipping industry. The major benefits when using additives with marine diesel fuels are: fuel savings, exhaust emission reduction, improved efficiency and reduced maintenance. Some additives like SulNOx have the potential to improve lubricity and combustion process in marine engines. The small percentage (3-5%) of fuel consumption could be achieved with additives, but even the smallest reduction could ensure significant fuel savings due to the high consumption of large slow-speed marine engines. This benefit could also improve efficiency and CII rating of the ship. Marine fuel additives, with their ability to reduce emissions, could bridge the gap in the transition from conventional diesel fuels to alternative fuels, due to lower costs, availability and a wide range of marine fuels and ships on which they could be applied.
Knežević et al. (Mon,) studied this question.