Renewable Energy for Marine Vessels

Marine transportation remains one of the most important sources of cargo transportation on Earth; however, it has been estimated that 60,000 premature deaths each year can be attributed to ship emissions (Hiricko 2008).  Marine vessels, which run on petroleum-derived diesel, are one of the largest contributors to air pollution, global warming, and premature deaths.  In order to reduce the high amount of greenhouse gas contribution and premature deaths Lin (2013) emphasizes the need to replace marine fuels, which contain sulfur, asphalt, and other environmentally harmful components, with a more environmentally friendly fuel (Lin and Lin 2006).  As a renewable and clean fuel, biodiesel has the potential to become the new leading energy source in the marine transportation sector; however, without large steps being taken to formulate marine biodiesel blends, reduce manufacturing costs, increase subsidies, and improve marine biofuel technology this potential will not be met. —Shelby Long
Lin, C.Y., 2013.  Strategies for promoting biodiesel use in marine vessels.  Marine
Policy 40, 8490.

Cherng-Yuan Lin of the National Taiwan Ocean University investigated the necessary development of biodiesel for the marine transportation sector.  He analyzed current emission limit requirements for marine vessels, environmental impacts of biodiesel, the biodiesel life cycle, obstacles for biofuel use in marine vessels, and strategies to overcome the obstacles.  Current and proposed emission limits for sulfur oxide and nitrogen oxide have been set by the International Convention for the Prevention of Pollution from Ships (MARPOL).  Biodiesel contains fatty acids and other contents that do not produce harmful emissions like petroleum diesels do when combusted, such as sulfur oxides.  Research shows that as the proportion of biodiesel blended into liquid fuel increases, the nitrogen oxide emissions decrease (Qi et al. 2011).  When analyzing the life cycle of biodiesel there are five stages that are taken into account:  feedstock production, transportation of feedstock, production of the fuel, distribution, and use of the fuel (National Biodiesel Board 2005).  Past studies have shown conflicting results over whether the total production of biodiesel requires more energy than it produces.  More specifically, a study by Pimentel and Patzek suggests that 118% and 27% more fossil fuel energy was used to produce sunflower and soybean oil biodiesel than total biodiesel oil was produced (Pimentel and Patzek 2005).  However, a more recent study by the National Renewable Energy Laboratory found that 320% of biodiesel energy is produced for every unit of fossil energy input during soybean biodiesel production (Sheehan et al. 1998).  These conflicting results can be accounted for by the lack of a precise definition for energy input and varying methods for calculating energy use within the biodiesel life cycle (National Biodiesel Board 2005).  An obstacle that remains for biodiesel use in marine vessels is the lack of a marine-grade biodiesel specification.  There are specifications for biodiesel use in land vehicles; however, marine vessels are very different in that they contain copper and other metal components which are susceptible to deterioration by biodiesel (Nayyar 2010).  Another obstacle is the large amount of farmland needed to grow the vast amount of feedstock required for the production of the biodiesel.  Lastly, Lin examines the low-temperature fluidity of biodiesel, which is a problem for marine vessels operating in colder climates.  As the surrounding temperatures decrease, crystals form in the biodiesel, which can plug the fuel lines.  
Lin suggests strategies to combat the various obstacles inhibiting the use of biodiesel in marine vessels.  In order to establish a marine biodiesel specification, he recommends that field tests must be conducted to determine the optimal mix of biodiesel and marine fuel using current ASTM biodiesel specifications and marine heavy fuel oil standards for density, viscosity, flash point, etc.  He recommends government subsidies, tax cuts, tax exemption, and fuel tariffs be made for marine-grade biodiesel to make it more price-competitive and to promote the long-term development of renewable marine biodiesels.  Previous studies have shown that an increase in the proportion of biodiesel to marine diesel results in decreased emissions from fishing boats (Lin and Huang 2012).  Therefore, if the amount of biodiesel were to be increased it would not only result in the decrease in the price of biodiesel due to economies of scale, but it would also reduce overall emissions.  Also, Lin suggests that storage tanks that are susceptible to deterioration from oxides reacting with biodiesel must be substituted with carbon steel, aluminum, fiberglass, or stainless steel tanks. 
In order to improve the fluidity of biodiesel in colder temperatures various combinations of biodiesel feedstocks must be tested.  Certain biodiesel types have a higher saturated fatty acid content, which creates a higher temperature at which crystals form and clog fuel lines; therefore, different feedstocks can be mixed in varying proportions to create an optimal blend that can withstand a desired temperature.  Lastly, Lin suggests that glycerol, a byproduct of the transesterification process of biodiesel production, can be purified and sold to the pharmaceutical, cosmetic, and other lucrative industries.  The selling of this glycerol surplus can be used to lower the price of biodiesel production and to decrease the environmental harm untreated glycerol can cause.  Although there are various obstacles that must be overcome in order to create a widely-used marine-grade biodiesel, these obstacles have feasible solutions.  Lin maintains that if these solutions are achieved and the renewable and clean biodiesel energy is used in the marine transportation sector, worldwide emissions will be reduced, thereby decreasing global warming and protecting people’s well-being.
Other Sources
        Hiricko, A. 2008.  Global trade comes home: community impacts of goods movement. Environmental Health Perspective 116, A78–A81.
         
        Lin, B. and Lin, C.Y. 2006.  Compliance with international emission regulations: reducing the air pollution from merchant vessels. Marine Policy, 30, 220–225.
        Lin, C.Y. and Huang, T.H. 2012. Cost–benefit evaluation of using biodiesel as an alternative fuel for fishing boats in Taiwan. Marine Policy 36, 103–107.
National Biodiesel Board. 2005. Response to David Pimentel biodiesel life cycle
analysis.
Nayyar, P. 2010. The use of biodiesel fuels in the U.S. marine. Report for the U.S.
Maritime Administration (MARAD).
        Pimentel, D. and Patzek, T.W. 2005. Ethanol production using corn, switchgrass, and wood; biodiesel production using soybean and sunflower. Natural Resources Research, 14, 65–76.
        Qi, D. et al. 2011. Effect of EGR and injection timing on combustion and emission characteristics of split injection strategy DI-diesel engine fueled with biodiesel. Fuel 90, 1884–1891.
Sheehan J. et al. 1998. Life cycle inventory of biodiesel and petroleum diesel for use
in an urban bus, final report. National Renewable Energy Laboratory, NREL/SR-580-24089 UC Category 1503.

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