IMO 2020 Reduces Sulfur Emissions, not CO₂

Ocean carriers can choose between three different methods to reduce their container vessel’s sulfur emissions. While each solution offers a significant decrease in SOx emissions, they all come with concessions when it comes to CO₂ or other greenhouse gas emissions. They consist in either:

• Using refined diesel fuels, or distillates such as marine gas oil (MGO), with sulfur contents below 0.5%. This fuel is more expensive than Heavy Fuel Oil (HFO).
• Installing scrubbers on their ships – essentially a washing machine that separates the sulfur from the rest of the fuel when it is burnt.
• Using alternative fuel sources like liquefied natural gas (LNG). LNG requires adapted engines but is relatively cheaper to purchase. Because of the hazardous nature of gas, it restricts the types of cargo transportable on the vessel.

Studies diverge on the true environmental costs of IMO 2020’s sulfur emissions reduction way forward. Each sulfur reduction method comes with observable drawbacks that, while they do not outweigh the benefits of IMO 2020’s, justify further research and policymaking.

By working with trusted partners, DHL can help customers not only reduce sulfur emissions, but also contribute to accelerating sustainable fuel production and global availability. Here is an example with Ocean Freight:

1. DHL forecasts the carbon emissions which shall be reduced.
2. The corresponding amount of sustainable marine fuel is ‘procured’ and used on one or several container vessels.
3. Carriers bunker the sustainable marine fuel, but only need to cover the cost of the conventional fuel. The price difference between conventional and sustainable marine fuel determines the cost for the sustainable fuel premium.
4. Applying the one-atmosphere approach simplifies the fuel switch, since the sustainable marine fuel does not have to be on the same vessels as the container whose emissions are to be reduced.

Not all low-sulfur fuels are created equal. Very Low Sulfur Fuel Oil (VLSFO) is obtained by blending additives and so-called aromatic compounds to enhance its efficiency and lubricity. These aromatic compounds, such as toluene or benzene, can create black carbon when in contact with the air.

Black carbon is an aerosol that results from incomplete fuel combustion, and the United Nations consider it to be a driver of climate warming, in addition to being toxic to humans. A study submitted by Germany to the IMO warns that the switch from sulfur-rich HFO to VLSFO may increase black carbon emission by up to 85%. The study also points out that operating ships at lower speeds may increase the emission of black carbon.

To comply with IMO 2020’s regulations, ship owners can install scrubbers onto their vessels. These scrubbers “wash” sulfur oxide off the vessels’ engine and exhaust systems, enabling for the usage of traditional HFO, with sulfur contents above 0.5%.

These scrubbers come in two categories: open- and closed-loop. Closed-loop systems store the waste water on the ship and require to be disposed of in dedicated port facilities. Open-loop systems, however, release the polluted water into the ocean, potentially harming ocean wildlife. Countries such as China are now considering enforcing policies that would ban open-loop scrubbers from their coastal regions going forward.

While using LNG decreases a vessel’s CO₂ emissions, LNG essentially consists of methane – technically still a fossil fuel and a greenhouse gas. In addition to the reduction of CO₂ emissions, the United Nations’ Intergovernmental Panel on Climate Change recommends reducing methane emissions by 35% or more by 2050, in comparison to 2010’s levels in order to contain global warming to 1.5° Celsius.

While the generation and distribution of LNG can raise CO₂ emission concerns, its normal combustion inside a ship’s engine creates less CO₂ emissions than that of HFO. However, suboptimal engine design enables leakage, also known as methane slip – the continuous emission of methane into the atmosphere. Such a phenomenon highlights the importance of better ship and engine design, along with thorough and regular emission measurement on board. This is in part the objective of IMO 2050’s Initial Strategy, which addresses the points raised by the studies presented above – and shippers can already act today.

Biofuels will remain one of the most realistic alternatives to traditional fuels, be they heavy or light in sulfur, for the next five to ten years. They must importantly be sourced from sustainable raw materials, but have the advantage to be widely commercially available today. With further supply chain optimization and economies of scale, they could be obtained at even lower prices in the future. When done correctly, both production and use of biofuels are also more environment-friendly, because the fuels are biodegradable and much less toxic than fossil fuels.

Biofuels commonly include:

• Biodiesel: Derived from vegetable or animal fats and alcohol, it is generally used as an additive to diesel fuels, with the blend ranging from 2% (B2) to 100% biodiesel (B100). When made of waste feedstock (or HVO, for hydrotreated vegetable oils) it can be used as a pure fuel.
• Bioethanol: It is used as an additive to conventional gasoline and usually produced through the alcoholic fermentation of corn or grain. The most widely known version is E10, used in passenger cars and in trucks, a blend of 10% ethanol and 90% gasoline.
• Biokerosene: Also known as biojet, it is produced from vegetable and animal fats. Biojet fuels can reduce greenhouse gas emissions in aviation by anywhere from 50% to 95% compared to fossil jet fuel.

Biofuels exist in parallel to e-fuels, which are synthetic fuels produced from water and carbon dioxide. Read about e-fuels and other advancements in our Sustainable Fuels white paper PDF (1.9MB).

Insetting Solutions: Switching to Sustainable Fuels

Understanding Sustainable Supply Chain Management

Focus on Sustainability Glossary