This research was performed with the goal of giving insight if the Rijksrederij is able to operate part of their fleet on renewable methanol and fuel cells, in order to work towards their goal of operating with net zero CO2 emissions by 2030. This prompted a research question that focussed on both the renewable methanol supply and the technical implementation on board of some of the ships operated by the Rijksrederij.
First, multiple possible pathways for renewably producing methanol were considered. Three main pathways were identified: two of which using waste biomass, one using recycled CO2 from on-board carbon capture. Green hydrogen could be provided using excess wind energy from Rijkswaterstaat’s own wind parks. In a later stage, it was found that a combination of biomass derived CO2 and recycled CO2 would be most beneficial to use in the methanol production process, by hydrogenating the CO2 with the beforementioned green hydrogen. However, this process resulted in net well-to-tank CO2 emissions.
To gain insight in all necessary components, a literature study was performed on maritime fuel cell systems and methanol reformers. Next, a model based on these systems was constructed that could be used in two ways: to aid in selecting specific systems and tank dimensions to be installed on board of ships, and to calculate tank-to-propeller CO2 emissions on both trip basis and yearly. Three different Rijksrederij ships were analysed using this model, and the spatial system integration on board was considered. In order to recycle the CO2 to produce green methanol, an on-board carbon capture system was needed and also modelled. The model is parametric in a way that allows for other ship types and fuel cell related systems to be used as input. In the end, the tank-to-propeller emissions for the three ship types were calculated, and these findings could be extended towards a larger part of the Rijksrederij fleet in order to calculate the entire well-to-propeller emissions of this fleet.
It was found that there were net positive emissions stemming from two sources: the aforementioned methanol production related emissions, and the slip stemming from uncaptured CO2 on board. Since not 100% of all CO2 could be captured on board, this also results in a gap in available CO2 for methanol production. In this sense, the production CO2 gap and the net well-to-tank emissions go hand in hand, and eliminating the net emissions (by capturing CO2 elsewhere, or improving the capture rate) also reduces the production gap. To achieve this, more research will be necessary.