Recently, there has been a lot of discussion in the public about LNG-powered ships, which were believed to be a low-emission solution for maritime transport. But according to measurements, they are not. Low-pressure LNG engines emit methane, which a much stronger greenhouse gas compared to CO2.
First, let’s go back a little bit in history. Shipping was allowed to be for a long time without worrying about the environmental pressures associated with its energy production. The world’s attention was largely on maritime oil and other accidents and the prevention of waste disposal to seas.
Crude oil pumped from the soil always contains sulfur, the amount of which varies in different oil drilling areas. Sulfur has been removed from car fuels already for decades. This process leaves high-sulfur fuel that could be used at sea until recent years. As a result, shipping has been the world’s worst producer of sulfur dioxide until these years. Sulfur dioxide reduces air quality and causes adverse health effects. It is highly soluble in water and causes acidification of soil and water.
About 10 years ago, the International Maritime Organization (IMO) decided to limit the sulfur content of marine fuels, first as early as 2015 in the Baltic Sea and other sensitive areas; and from 2020 worldwide.
An alternative fuel, without sulfur, was sought for this need. Traditional natural gas, or LNG, was found. It contained no sulfur at all, and its use also reduced nitrogen emissions by up to 85% and CO2 emissions by 25%. It was already understood at that time that, as far as carbon dioxide is concerned, LNG as a fossil fuel is only a temporary solution, but then no better commercially available solutions were known. Other solutions to reduce sulfur emissions were low-sulfur fuel, as well as sulfur scrubbers that remove sulfur from the exhaust gases.
Several new ships burning LNG were also introduced in Finland. The first Viking Grace was already in 2012, when it was definitely a state-of-the-art in the industry. Gradually, soon after, however, measurements began to be heard that although the burning of LNG reduced CO2 emissions, methane, a multiple of greenhouse gas emissions, was released into the air during the combustion process.
On the other hand, the results were complex. Slow, two-stroke, high-pressure engines emit hardly any methane, but some of the faster, four-stroke engines emit significantly more methane. This also depends on the pressure at which the motors are operated. However, the situation is constantly under development and engine manufacturers are developing lower-emission LNG engines.
Over the last couple of years, the focus on shipping has shifted more and more to CO2 emissions. Shipping currently accounts for less than 3% of global greenhouse gas emissions.
In June 2021, the International Maritime Organization (IMO) has set a target of halving greenhouse gas emissions from shipping by 2050 compared to 2008. In July 2021, the European Commission presented the Fitfor55 package, which included proposals to include shipping in emissions trading, fuel carbon distribution, tax exemptions and alternatives.
For several years now, the shipping industry has been working hard to develop carbon-neutral fuels. Work is underway on methanol, ammonia, hydrogen, electricity, nuclear power, wind and solar power, etc. Developments are tremendous, but there is currently no fuel that is commercially ready to replace heavy fuel oil or LNG. In a few years, the situation will be different.
At present, the greatest opportunities for reducing CO2 emissions from shipping are operational, e.g. a reduction in the speed of the ship, or non-fuel technologies such as improving the efficiency of engines, reducing the resistance of the ship’s bottom, etc. The advantage of existing LNG carriers is that in the future they can easily use other more environmentally friendly gaseous fuels.
LNG has thus been a major step towards sulfur-free shipping, but the next steps are being taken towards ships with minimized CO2 emissions.