Natural Gas as a Marine Propulsion Fuel: Energy and Environmental Benefits in Urban Ferry Service

Although transportation has major energy and environmental policy implications, not all sectors are treated equally, and ships often are overlooked. However, ships are a significant source of air pollution and account for a nontrivial portion of U.S. petroleum demand. Moderate emissions standards for new marine engines have been proposed by the Environmental Protection Agency, but these will take well over a decade to become effective once they are enacted, and there are no energy policy provisions for ships. Nonetheless, ships offer cost-effective options for both emissions reductions and the use of alternative fuels. Aware of these issues, the U.S. Department of Energy’s Office of Transportation Technologies and the Gas Research Institute sponsored a study of the potential use of natural gas as the fuel for passenger ferries as part of their Natural Gas Vehicle Technology Initiative. The results of the study are discussed, with a focus on the energy and environmental issues related to maritime operations in the United States. The challenges and opportunities of a specific project to design, construct, and operate several natural gas-powered ferries in Boston Harbor are discussed. A significant reduction in air pollution and a large increase in the use of natural gas as a transportation fuel are expected from this project, but the greenhouse gas emission impacts are ambiguous. Further, an emissions monitoring and analysis program is described that would greatly improve the accuracy of maritime emissions inventories and would enable ships to take part in existing emissions trading programs in port cities around the country. Such a development would create significant economic incentives to encourage ferry owners to invest in clean fuel technologies, which could have major implications for energy and environmental policy.