Economic and population growths are the most important drivers of growing global energy demand. They led to a rapid development of international seaborne trade and an increase in the number of global vessels. Air pollution from these ships is of great concerns and regulations are currently enforced since May 2005 by the International Maritime Organization to limit such pollution. In this study, we will first review the current global energy demand and its driving forces over next decades, second evaluate the existing alternative fuels that can be used as a bunker fuel to reach sustainability with relatively small changes in the existing marine propulsion options and finally focus on near-term solution, which has the potential for large-scale use. The different alternative fuels were compared in terms of several parameters such as availability, renewability, safety, cost, performance, economy and compliance with emission regulations. This comparison revealed that liquefied natural gas could be considered as the future replacement to the current marine bunker fuel. This conclusion has been further verified by comparing diesel engine with different powers when using both heavy fuel oil and liquefied natural gas. The engines were compared against fuel consumption, cost saving as well as emissions. Liquefied natural gas has proved to be better than heavy fuel oil due to fuel cost reduction by about 31% per year and decrease in emissions of SO _x , NO _x , CO ₂ and particulate matter by about 98%, 86%, 11% and 96%, respectively. The resulted emissions from using liquefied natural gas were found to comply with the current International Maritime Organization regulations. Moreover, this article highlights the latest rules and regulations that govern the use of liquefied natural gas as marine fuel onboard ships.

One of the main causes of climate change and global warming is greenhouse gas emissions. Livestock makes up 15% of the world's greenhouse gases (GHG), whereas maritime shipping accounts for 3%. Cattle can produce about 500 grams of methane a day per cow. This study demonstrates that livestock ships are an extremely high source of methane emissions. This study also offers innovative scientific techniques for lowering methane gas emissions from livestock ships, techniques that you, as researchers, scientists, environmentalists, and policymakers, can help implement. The MV Gelbray Express Livestock ship was selected to investigate the overall emissions generated by the main engine and the livestock on board. Main engine CO2 emissions and livestock CO2 equivalent emissions are theoretically calculated during 24-hour sailing under engine full load and livestock full capacity. The study revealed that livestock CO2 equivalent emissions account for 43% of the total CO2 emissions emitted by the engine and the livestock. ZELP (Zero Emissions Livestock Project) has patented a unique catalytic technique for capturing and neutralizing methane generated during enteric fermentation in ruminant animals such as cows to decrease livestock methane emissions. Theoretical results show that using the ZELP mask reduces CO2 equivalent emissions by 58 000 kg per day at a livestock capacity of 4000 cattle onboard the MV Gelbray Express Livestock ship. Keywords: climate change; international maritime organization; Zero Emissions Livestock Project. Redução das emissões de metano em navios de transporte de gado para mitigar as emissões de gases com efeito de estufa e promover a sustentabilidade marítima transporte futura RESUMO: Uma das principais causas das mudanças climáticas e do aquecimento global são as emissões de gases de efeito estufa. A pecuária representa 15% dos gases de efeito estufa (GEE) do mundo, enquanto o transporte marítimo é responsável por 3%. O gado pode produzir cerca de 500 gramas de metano por dia por vaca. Este estudo demonstra que os navios de transporte de gado são uma fonte extremamente alta de emissões de metano. Este estudo também oferece técnicas científicas inovadoras para reduzir as emissões de gás metano de navios de transporte de gado, técnicas que você, como pesquisadores, cientistas, ambientalistas e formuladores de políticas, pode ajudar a implementar. O navio de transporte de gado MV Gelbray Express foi selecionado para investigar as emissões gerais geradas pelo motor principal e pelo gado a bordo. As emissões de CO2 do motor principal e as emissões equivalentes de CO2 do gado são calculadas teoricamente durante a navegação de 24 horas sob carga total do motor e capacidade total do gado. O estudo revelou que as emissões equivalentes de CO2 do gado são responsáveis ​​por 43% das emissões totais de CO2 emitidas pelo motor e pelo gado. O ZELP (Zero Emissions Livestock Project) patenteou uma técnica catalítica exclusiva para capturar e neutralizar o metano gerado durante a fermentação entérica em animais ruminantes, como vacas, para diminuir as emissões de metano do gado. Resultados teóricos mostram que o uso da máscara ZELP reduz as emissões de CO2 equivalente em 58.000 kg por dia em uma capacidade de gado de 4.000 cabeças de gado a bordo do navio MV Gelbray Express Livestock. Palavras-chave: mudança climática; organização marítima internacional; Projeto Pecuária Emissão Zero.

This study examines the issue of diesel emissions from vehicles and vessels and their impact on environmental degradation with a focus on nitrogen oxide (NOx) emissions and their contribution to air pollution-related deaths worldwide. The novelty of this work is the use of computational fluid dynamics simulations to investigate the effectiveness of water addition for reducing NOx emissions. This study considers two methods of water addition, i.e., injection of water and air into a combustion chamber and mixing of water with fuel before injection. Adding water to air systems at 10% and 20% ratios reduces NOx emissions by 5% and 10%, respectively, whereas mixing water with fuel at the same ratio reduces NOx emissions by 25%. Increasing the water percentage can further reduce emissions by up to 35%. This study indicates that water addition is a cost-effective method for reducing emissions, and numerical analysis is crucial for demonstrating its effectiveness.