The U.S. Department of Energy (DOE) Bioenergy Technologies Office (BETO) invests in research, development, and demonstration of low- and net-zero-carbon sustainable marine fuels to help decarbonize maritime transport.
International maritime transport accounts for approximately 3% of global greenhouse gas (GHG) emissions, this includes a wide variety of vessels, from small recreational boats to massive, ocean-going container ships. Although smaller marine vessels may be powered by batteries or hydrogen fuel cells, many larger vessels need energy-dense fuels to support global voyages.
With a far lower carbon footprint than petroleum-based fuels, sustainable marine fuels are critical for lowering GHG emissions, achieving environmental justice, and promoting energy security in the maritime sector.
Sustainable Marine Fuels Lower Greenhouse Gas Emissions
More than 90% of global goods are carried by cargo ships, and many of these ships are powered by heavy fuel oil (HFO), a residual fuel produced from petroleum refining which emits relatively large amounts of GHG when combusted. Sustainable marine fuels are a recognized pathway for lowering GHG emissions compared to HFO and other petroleum-based marine fuels.
Sustainable marine fuels are produced using a variety of materials, methods, and technologies that convert domestic fuel resources—called “feedstocks”—into energy-dense fuels with the correct properties and characteristics to be safely used in marine engines.
These feedstock types include:
- Forestry and agricultural wastes
- Non-food energy crops like switchgrass and miscanthus
- Waste oils, fats, and greases
- Manure, sewage sludge, and other wet wastes
- Landfill gas
- Algae biomass
- Municipal solid waste.
To maximize the emission advantage, BETO research focuses on near-term and emerging marine biofuels with the potential for negative or near-negative life cycle GHG emissions.
Drop-in sustainable marine fuels can be used in existing infrastructure and marine engines without major modifications. As a result, marine vessels may begin using these fuels in as little as a few years to support immediate reductions in GHG emissions. Examples include:
- Renewable diesel
- Hydrotreated vegetable oil
Emerging Marine Fuels
The maritime industry is also pursuing emerging sustainable marine fuels with the potential for zero or near-zero GHG emissions, including:
- Lignin-alcohol mixes
- Bio-based natural gas.
These emerging marine fuels offer flexibility and some performance advantages but may require new engine designs and other mechanical modifications. Some global shipping companies have already announced plans to use these fuels in the coming years.
A Pathway for Improving Air Quality in Port Communities
HFO and other petroleum-based marine fuels often contain relatively high levels of sulfur, which is emitted as sulfur oxide during combustion. This, along with other toxic air pollutants created during combustion, contributes to poor air quality for the millions of people that live close to seaports.
Sustainable marine fuels are a reliable solution for improving air quality and supporting environmental justice in port communities without the need to add costly emissions controls to marine engines. Naturally low in sulfur, sustainable marine fuels produce lower levels of air pollutants, including:
- Sulfur oxide
- Nitrogen oxides
- Particle pollution.
As a result, the maritime industry is better equipped to meet increasingly stringent air quality regulations set by the International Maritime Organization.
Strategic Research Lowers the Risk of Adoption
According to BETO’s 2016 Billion Ton Report, the United States has enough feedstocks to sustainably produce millions of gallons of sustainable biofuels every year. Every year, the global maritime industry consumes an estimated 105 billion gallons of fuel, which is expected to double by 2030 as global trade expands. To increase production of sustainable marine fuels to meet this demand, the industry needs reliable analyses and data to:
- Understand regulatory requirements
- Scope biofuel performance
- Address challenges to large-scale commercialization.
BETO supports research designed to guide investments in demonstration and deployment of sustainable marine fuels. This includes a whole-system approach to ensure the maritime sector can reap the advantages of sustainable marine fuels without shouldering significant risks:
- Analyses to understand costs, emissions, and resource constraints, as well as social and environmental implications
- Combustion/engine testing to understand how sustainable marine fuels interact with current and future marine vessels
- Fuel property and consumption assessments to ensure new fuels meet quality standards
- Pilot-scale demonstrations of promising production technologies, such as hydrothermal liquefaction and pyrolysis, to lower the risk of commercial production at refineries across the country.
Supported by capabilities and expertise from DOE national laboratories, BETO works across DOE offices and other federal agencies for a strategic approach for building a robust and stable economy for production and use of sustainable marine fuels.
DOE is a member of Mission Innovation, an initiative of 22 countries and the European Commission to accelerate progress toward net zero GHG emissions. As a co-lead for the initiative’s Zero-Emissions Shipping Mission, DOE coordinates international efforts with other countries, private industry, research organizations, and communities to set international shipping on an ambitious zero-emission trajectory.