Publication Details

Title : Environmental Assessment of Alternative Fuels for Maritime Shipping
Publication Date : September 27, 2021
Authors : G Zaimes, J. Stuhr, E. Tan, K. Ramasamy, J. Askander, M. Kass, B. Kaul, T. Hawkins
Abstract : Maritime shipping is undergoing a historic transformation period, catalyzed by recently promulgated restrictions on marine fuel sulfur content and a heightened regulatory focus on maritime decarbonization. The International Maritime Organization (IMO), the governing body of international shipping, has set aggressive targets aimed at reducing the carbon intensity of marine vessels, with an overall goal of 50% reduction in greenhouse gas emissions (GHG) from international shipping by 2050, relative to 2008 levels, and pursing efforts to phase out GHG emissions by the end of this century. In 2020, IMO set new regulations that restricted marine fuel sulfur content to 0.5% by weight, and issued a carriage ban on all non-compliant fuel. These regulations are reshaping the marine sector's energy landscape and driving the deployment of low-carbon and low-sulfur alternative fuels for marine transport. Among alternatives, biofuels are a promising option due to their low sulfur content, high energy density, compatibility with existing fuel infrastructure, and low carbon intensity.

Holistic environmental systems analysis is critical for quantifying the broad-based environmental impacts of alternative fuels for marine applications and their capacity to meet long-term IMO GHG reduction targets. Thus, it is essential for guiding the sustainable development of the maritime sector. In this work, life cycle assessment (LCA) is performed to quantify the environmental performance of several novel marine biofuels systems including: (1) hydrothermal liquefaction (HTL) biocrude from waste sludge, (2) catalytic fast pyrolysis bio-oil, (3) biogas-to-liquids via Fischer Tropsch, (4) renewable fuels derived from the heavy cut of the aviation biofuel pool, and (5) lignin ethanol oil (LEO). These systems are conceptually appealing in the context of marine applications due to their capacity to produce minimally processed fuels (e.g., HTL biocrude, bio-oil). They can be blended with existing maritime fuels or further upgraded to be fungible with existing marine infrastructure and vessels.

In this work, Argonne’s Greenhouse Gases, Regulated Emissions, and Energy Use in Technology (GREET) model is used to characterize the life cycle environmental impacts of marine biofuels across multiple environmental metrics and benchmark the results against conventional Heavy Fuel Oil (HFO) as well as leading alternative marine fuels. LCA results are also coupled with Argonne's Maritime AGE model and used to track the life cycle environmental impacts of alternative marine fuel deployment at scale, based on projected global maritime fuel consumption reported in IEA’s Sustainable Development Scenario for international shipping. This 'macro-level' perspective is complementary to traditional LCA results which are presented on a per unit energy basis. Preliminary LCA results indicate that biofuels can achieve up to 86% reduction in life cycle GHG emissions relative to HFO, and thus show technical merit for meeting IMO's long-term GHG reduction targets. Moreover, biofuels demonstrate reduced life cycle sulfur oxide emissions relative to HFO but exhibit several environmental tradeoffs such as higher water-footprint. Synthesis of these results provides a broad-based understanding of the environmental benefits and challenges of alternative fuels for maritime shipping and technical direction to guide research and development in next-generation marine fuels.

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