United States – Researchers at the National Renewable Energy Laboratory (NREL) and other Department of Energy institutions are looking at the use of marine biofuels as part of a global effort to reduce sulfur and greenhouse gas (GHG) emissions from ships.
“Biofuels turned out to be very good options because they have zero or very, very low sulfur compared to fossil fuels,” said Eric Tan, a Senior Research Engineer at NREL and lead author of a new article published in the journal Environmental Science and Technology.
Reducing sulfur oxides emissions has major benefits
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%. 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, 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. To reduce emissions, shipowners can either install sulfur scrubbers or switch to a low-sulfur fuel. Both solutions come with a price tag.
The NREL-funded study is a good starting point for determining if ships can run on biofuels. Fuel expenses already make up a large portion of the cost of operating a shipping line, thus the researchers looked at both pricing and emissions.
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.
Biofuels from biomass offer higher GHG emissions reductions
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.
According to Tan’s research, the United States has a huge source of bio-feedstocks for producing huge amounts of marine biofuels to replace fossil fuels assuming transportation is unaffected by competition. With 400 million metric tons of gasoline used annually by ships, a biofuel mixture of 5% equals to 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.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by the Alliance for Sustainable Energy.