Amid new scientific evidence that most black carbon present in the Arctic is from burning fossil fuels, the International Maritime Organization (IMO) agreed last week that there are up to 41 appropriate ways to reduce black carbon from ships at the sixth session of its Pollution Prevention and Response subcommittee. Thirteen of those were also recommended as appropriate black carbon control measures by participants of the ICCT’s fifth workshop on marine black carbon emissions. Now that IMO has agreed that we can control black carbon, will we?
Black carbon is a small, dark particle that absorbs sunlight and heat, warming the atmosphere and melting snow and ice when it falls to the ground. After carbon dioxide, black carbon is the second largest driver of global warming. In addition to its climate impacts, black carbon is an air pollutant, aggravating the respiratory system and contributing to heart and lung disease. Because black carbon is a “short-lived” pollutant, staying in the atmosphere for only a few days or weeks, reducing black carbon emissions has immediate climate and health benefits.
Ships emit black carbon when they burn fossil fuels such as heavy fuel oil (HFO). In our global shipping emissions inventory, we found that black carbon accounts for more than 20% of carbon-dioxide equivalent emissions from ships over a 20-year timeframe, making it a significant climate warming pollutant. To reduce black carbon, IMO agreed that ships can use cleaner fuels such as distillate fuels, which reduce black carbon by 33% compared to HFO, or liquefied natural gas (LNG), which emits nearly zero black carbon. Less commonly used fuels, such as biodiesel and methanol could also reduce black carbon emissions from an individual ship by 55-75%. Alternatively, ships can remove black carbon from exhaust using diesel particulate filters (DPFs) or electrostatic precipitators (ESPs), each of which reduce black carbon by more than 90%. Of course, zero-emission technologies such as batteries and hydrogen fuel cells eliminate black carbon emissions from the ship, as we show in our new working paper on transitioning away from HFO in Arctic shipping.
IMO delegates will start considering potential black carbon control policies in May at the next Marine Environment Protection Committee meeting. Proposals may include setting black carbon emissions limits for marine engines and ship exhaust, and a ban the use of high black-carbon fuels, such as HFO, in the Arctic. At PPR 6, delegates began developing a ban on using and carrying HFO as fuel for ships in the Arctic, aiming to agree to a ban by 2021 and begin enforcement in 2023. Banning HFO can reduce black carbon emissions by 33% if ships switch to distillate fuels. Larger reductions can be achieved if ships use alternative fuels such as methanol, oxygenated biofuels, or LNG (although fugitive methane emissions could still harm the climate). Black carbon from ships outside IMO’s narrow definition of the Arctic should also be reduced.
The ICCT will be hosting its sixth workshop on marine black carbon emissions this fall. Our goal will be to identify potential black carbon control policies. These could include certifying new engines to low black carbon emissions, requiring existing ships to use cleaner fuels, removing black carbon from the exhaust using DPFs or ESPs, or other measures.
As the Arctic continues to warm at twice the rate of the rest of the planet, we’re reminded that reducing black carbon emissions delivers immediate climate benefits. The best time to cut black carbon emissions was decades ago. The next best time is today.