Climate change is a major challenge facing humanity today. Since the First Industrial Revolution, the large-scale use of fossil energy has driven human development, but it has also led to serious global warming. The 28th Conference of the Parties to the United Nations Framework Convention on Climate Change (COP28), held in Dubai, UAE, in 2023, ultimately agreed on a roadmap for transitioning away from fossil fuels, which is seen as the beginning of the end of fossil fuels. Currently, over 150 countries worldwide have announced their goals of achieving zero carbon emissions or carbon neutrality by around 2050.
Dimethyl Ether: An Ideal Green Fuel for Ship Propulsion
Towards the goal of carbon neutrality, the world is facing an unprecedented green energy transition from fossil fuels to renewable energy, with renewable energy transitioning from supplementary energy to primary energy.
Maritime shipping is currently the first major application area for renewable green fuels. Currently, 99% of the world’s ocean vessels are powered by reciprocating internal combustion engines. Given the long voyages, large tonnage, and complex environments of ocean shipping, new energy propulsion options, such as pure electric and fuel cells, are difficult to adapt due to their power density, reliability, and cost. Internal combustion engines will remain the primary propulsion system for future marine vessels. Therefore, developing renewable green fuels is a fundamental path to achieving decarbonization and net-zero carbon emissions in ocean shipping.
Dimethyl ether (DME) is non-toxic and environmentally friendly, with a high cetane number, making it an ideal fuel for compression-ignition marine engines. A summary of DME’s physical and chemical properties is shown in the table below.
The production of green DME is very similar to methanol production, with two main routes: synthesizing DME from green hydrogen and CO generated by biomass gasification; and synthesizing DME from green hydrogen and CO2 captured from carbon capture. Carbon capture can be industrial carbon capture, carbon capture from biomass combustion, and future direct air carbon capture (DAC). DME can also be produced from methanol, which already has a large market share, by dehydrating it.
The unique advantages and broad prospects of dimethyl ether
From a fuel compatibility and environmental perspective, methanol (MeOH), dimethyl ether, and ammonia are all considered carbon-neutral or zero-carbon fuels. However, because engines fueled by methanol and ammonia require diesel for ignition, especially under low-load conditions, pure diesel operation is required. This makes it difficult for marine engines using these fuels to achieve zero carbon emissions. In contrast, dimethyl ether, thanks to its excellent compression ignition characteristics, requires no pilot fuel and can operate on a single fuel. Its fuel system is simple and reliable, enabling net-zero carbon emissions. From a large-scale production economic perspective, the costs of methanol, dimethyl ether, and ammonia fuels are largely dependent on the price of green electricity. With the rapid advancement of photovoltaic and wind power technologies, the cost of green electricity generation will continue to decline. At the same time, global carbon constraints, such as EU carbon tariffs, carbon quotas, and carbon incentives and penalties, will further reduce the green premium of renewable fuels. From a fuel safety perspective, methanol is toxic, ammonia is highly toxic, and dimethyl ether is non-toxic and environmentally friendly. Therefore, compared to methanol and ammonia, dimethyl ether offers distinct advantages in engine compatibility, environmental friendliness, and safety.
Dimethyl ether (DME) has been successfully used in automotive engines. At the end of the last century, institutions such as the Technical University of Denmark, Haldor Topsoe A/S, Navistar, AVL, and AMOCO conducted research on the application of DME in compression-ignition engines. In China, Shanghai Jiao Tong University overcame technical challenges in DME’s low-NOx combustion, material compatibility, lubrication, and wear, successfully developing a DME-based automotive engine. Shanghai Jiao Tong University further collaborated with Shanghai Automotive Industry Corporation and Shanghai Diesel Engine Co., Ltd. to develop my country’s first DME-based city bus with independent intellectual property rights. This bus was included in the National Development and Reform Commission’s 166th “Announcement on Vehicle Manufacturers and Products” and successfully achieved international commercial operation on Shanghai Bus Route 147. These efforts have laid a solid foundation for the application of DME fuel in marine engines.
Today, the global shipbuilding and shipping industries are accelerating their transition away from fossil fuels. Green DME fuel offers the most promising solution for decarbonizing marine power.
