Biofuels Offer a Cost-Effective Way to Lower Shipping Emissions

(Argonne National Laboratory/Tech Xplore) Marine shipping traffic has grown steadily over the past decade—and so have the associated greenhouse gas emissions. Carbon emissions from ships grew almost 10% between 2012 and 2018, and the industry is a large consumer of petroleum fuel.

Substituting biofuel could reduce the amount of greenhouse gases and other pollutants entering the air from ocean shipping, according to a study from researchers at the U.S. Department of Energy (DOE) and Department of Transportation. Compared with conventional heavy fuel oil, the study found, biomass-based fuel could reduce greenhouse gas emissions between 40 and 93%.

Without any changes to the status quo, greenhouse gas emissions from shipping in 2050 could be 40% higher than they are today, according to the United Nations' International Maritime Organization (IMO). The IMO has set a target to instead cut those emissions by at least half.

Shipping is also a key source of sulfur oxides and soot or particulate matter emissions, which worsen air quality and have been linked to human health problems. The IMO recently imposed new fuel standards aimed at reducing emissions of sulfur oxides, requiring lower concentrations of sulfur in shipping fuel.

"The push to cut pollutants from shipping is an emerging opportunity for biofuels, but the potential impact has gone relatively unexplored," said Troy Hawkins, a scientist at DOE's Argonne National Laboratory who co-led the study, published in the journal Environmental Science & Technology. "Our analysis found biofuels can significantly reduce shipping emissions while remaining cost-effective."

The vast majority of cargo ships today run on heavy fuel oil, which is cheap and energy dense but very dirty to burn.

"These engines are multiple stories tall and so large you could climb inside them," Hawkins said. "They are just huge, and they are burning hundreds of millions of tons of thick, tar-like fuel to move freight internationally."

The study evaluated costs and emissions of biofuel alternatives including bio-oil and renewable diesel made from wood waste or fats such as used cooking oil. They also looked at mixtures of these biobased feedstocks with petroleum-based feedstocks including petroleum, natural gas and coal.

Across the board, the biofuels lowered emissions of greenhouse gases, sulfur oxides and particulate matter—and at costs that could be competitive with heavy fuel oil, after considering incentives such as California's Low Carbon Fuel Standard. Due to the low sulfur content of the biobased feedstocks, the biofuels analyzed reduced sulfur oxides emissions by 97% or more; particulate matter emissions came down between 84 and 90%.

Recently, DOE also announced a partnership with the governments of the United States, Denmark and Norway to develop technologies for zero-emission shipping as part of Mission Innovation, a global initiative to accelerate affordable, accessible clean energy solutions.

The datasets developed in the recent study are publicly available and could also support the evaluation of fuels to meet California's Low Carbon Fuel Standard, which takes a similar life-cycle view of fuels to encourage options with the lowest carbon intensity. READ MORE