US NREL examines potentials of marine biofuel use

A global effort to reduce sulfur and greenhouse gas (GHG) emissions from ships has researchers from the US National Renewable Energy Laboratory (NREL) and other Department of Energy facilities investigating the potential use of marine biofuels.

“Biofuels turned out to be very good options because they have zero or very, very low sulfur compared to fossil fuels,” Eric Tan, a senior research engineer at NREL and lead author of a new article published in the journal Environmental Science and Technology, said.

As explained, the NREL-directed research, “Biofuel Options for Marine Applications: Techno-Economic and Life-Cycle Analyses“, provides a starting point for establishing the feasibility of ships using biofuels. Fueling costs already account for a significant part of running a shipping line, so the researchers examined both prices and emissions.

The International Marine Organization (IMO) has been ratcheting down the allowed amount of sulfur oxides emissions from ships since 2005. The newest upper limit, which took effect at the start of 2020, reduced the sulfur content of ships’ fuel oil to 0.5% from 3.5%.

The IMO said the reduction should have major benefits for the environment and the health of people, particularly those living near ports and along coasts. Additionally, the IMO has set aggressive targets to decarbonize marine shipping, targeting at least a 50% reduction in GHG emissions from international shipping by 2050, relative to 2008 levels.

The new regulation, which is enforced by individual countries, requires changes to bring ships into compliance. Ship owners can either install sulfur scrubbers to reduce emissions, or they can adopt a different, low-sulfur fuel. Both options carry an additional cost.

The economics are weighed against the cost of burning heavy fuel oil (HFO), which accounts for about three-quarters of the fuel used by ships. A low-sulfur HFO costs slightly more a gallon than traditional HFO. The low-sulfur HFO prices would be the maximum ship owners are willing to pay for biofuels for a one-to-one replacement. The biofuels are considered to be potential drop-in fuels compatible for use in marine engines, but further work is needed to confirm that compatibility.

Upon examining different types of fuels for their ability to reduce emissions of greenhouse gases and air pollutants, the researchers found biofuels produced entirely from biomass offer much higher reductions in life-cycle greenhouse gas emissions—from 67% to 93% less than HFO. Biomass-derived fuels also are mostly free of sulfur and exhibit reductions in criteria air pollutant emissions such as particulate matter.

Tan’s research concluded that, if shipping had no competition, the United States has a large supply of bio-feedstocks for producing substantial amounts of marine biofuels to displace fossil fuels. With ships using 400 million metric tons of fuel annually, a blend of 5% biofuels translates to about 5 billion gallons.

The research was funded by the U.S. Department of Energy’s Bioenergy Technologies Office and by the U.S. Department of Transportation Maritime Administration.

ABS issues guidance on the use of biofuels in shipping

The NREL research coincided with the publication of a whitepaper examining the potential of biofuels in shipping by the American Bureau of Shipping (ABS).

“The Sustainability Whitepaper: Biofuels as Marine Fuel” gives an overview of the various types of marine liquid biofuels that are “drop-in” fuel options for replacing conventional fuels in both the near- and long-term and their potential to contribute to industry decarbonization goals. Other aspects considered include safety, vessel design implications and regulatory challenges.

“Biofuels have been identified as highly promising carbon neutral fuels that can enter the global market relatively quickly and help approach the IMO GHG reduction targets for 2030 and beyond. Being produced from renewable biomass, biofuels have the potential to offset the carbon emissions of a vessel due to the CO2 absorption of the feedstock, which can help counterbalance the combustion emissions,” Georgios Plevrakis, ABS Director, Global Sustainability, explained.

“However, the total carbon reduction potential of different biofuels clearly depends on a range of factors related to their value chain.”

He added that the guidance is aimed at fully informing owners, operators, shipbuilders and equipment manufacturers about the potential of this marine fuel.