It's not all about what comes out of the chimney

Fossil-free fuels do not automatically result in zero emissions. According to a new report from Lighthouse and the Swedish Transport Administration, ships running on hydrogen, methanol or ammonia in 2030 will reduce their real greenhouse gas emissions by 60-80 percent. It all has to do with the life cycle of the fuel. The energy carrier with the greatest potential to reduce climate impact is direct electrification.

“The more renewable energy in the electricity system, the more we can reduce the climate impact. With wind power alone, we could achieve an 80-90 percent reduction with hydrogen, ammonia or methanol, but with the electricity mix we are estimated to have in the Nordics in 2030, we end up with between a 60-80 percent reduction”, says Selma Brynolf, researcher at Chalmers and one of the authors behind the report Hydrogen, ammonia, and battery-electric propulsion for future shipping.

The report is the result of a four-year research project whose purpose has been to deepen life cycle knowledge about the environmental and economic sustainability of various ways to reduce greenhouse gas emissions in shipping using hydrogen, ammonia and direct electrification.

When it comes to alternative fuels, a lot has of course happened in four years, both hydrogen and ammonia, for example, have become new aspirants to the shipping fuel of the future.

“In terms of policy, fuels that do not contain carbon atoms have often been pushed forward because it is the easiest – after all, no carbon dioxide comes out of the ship's chimney. But in a life cycle perspective, the differences in climate impact are not that great between ammonia, hydrogen and methanol, but they move roughly within the same range of uncertainty.”

However, it can differ in other aspects, for example security, explains Selma Brynolf.

“There are major challenges there with ammonia, which is toxic and may never work on passenger ships. There are also large differences in how technically mature the various fuels are. Methanol has been tested the longest and is the most mature technology. We have also looked at costs and there the infrastructure cost for hydrogen is very uncertain. At the same time, hydrogen and ammonia can become somewhat cheaper than methanol, it depends a lot on what the carbon dioxide in methanol will cost and on availability.”

It is usually said that the solution to shipping's transformation will never be about a single fuel, but different fuels will be suitable for different types of ships. Electricity will be suitable for smaller ferries on shorter distances, while hydrogen can go a little longer, for example between the Swedish mainland and Gotland, for which Gotlandsbolaget's future Horizon series is intended. But what fuel will be used across oceans?

“It points to ammonia or methanol. One could also imagine some kind of biodiesel, but the raw material for that is limited and we have not investigated the bio-alternatives that much in this project.”

Selma Brynolf describes the research project - which has been carried out within the framework of the Swedish Transport Administration's industry program Hållbar sjöfart (sustainable shipping) run by Lighthouse - as an enabler for Swedish research to keep up with developments.

“Thanks to the project, we have been able to follow the IMO's development of its guidelines for life cycle analyzes and also contribute a little. Their guidelines roughly follow the way we calculated in our study on life cycle analyses.”

The report also shows that reduced climate impact can come at the expense of several other environmental impact categories, such as human toxicity, water use and resource use (minerals and metals), and furthermore the risk of eutrophication is high when using ammonia.

For the same type of fuel, fuel cells have greater potential to reduce environmental impact than internal combustion engine alternatives – however, engines are more competitive from a cost perspective.

The report Hydrogen, ammonia, and battery-electric propulsion for future has been authored by: Selma Brynolf, Fayas Kanchiralla and Elin Malmgren at Chalmers. Joanne Ellis and Tobias Olsson at RISE (formerly SSPA). Julia Hansson and Erik Fridell at the IVL Swedish Environmental Institute.