As we strive for ambitious greenhouse gas reductions, an anticipated shift in ship fuels will have an impact far beyond the engineroom.
What would a fuel designed by the devil look like? It would be a horror hidden in a package of perfection. Plentiful, cheap and easy to handle, it would possess exceptional energy density and just one problem: the more you use it the more damage you do. It would, one might argue, look a lot like oil.
As shipping contemplates a future in which oil plays a shrinking role, it is possible that we will never find a similarly perfect source of energy for our power and propulsion needs. In particular, all the proposed ‘future fuels’ suffer from a similar problem: volume. As one hydrogen propulsion engineer told me last week: “Maybe sooner than we think, the days of extremely compact fuels will be gone.”
This is not a new problem and has already hindered the uptake of LNG as a marine fuel. At half the energy density of diesel, naval architects must wrangle with fuel tanks twice the size of those needed for heavy fuel oil. Only now are ships being built with tanks big enough (and pressurised enough) to consider global operations. The calorific value per tonne of liquified hydrogen is half again that of LNG, while batteries remain far too heavy to consider for long voyages.
The inevitable conclusion, according to my hydrogen interviewee, is that shipowners will need to get used to building bigger ships. “If all ships had to be made bigger to allow storage of fuel, would that do any harm to global shipping? [It may] cost a bit more, but when everyone has to, that doesn’t matter anymore.”
Researchers at the UCL Maritime Advisory Service (UMAS) and Lloyd’s Register have a different idea. Discussing their study ‘Zero-Emission Vessels: Transition Pathways’, launched this week, they noted that new fuels would imply not a change in ship dimensions, but instead a shift in shipping operations. Less energy dense fuels would not mean bigger ships, but more frequent bunkering.
For vessels that cannot make more bunker calls - globally tramping vessels on the spot market, for example – the authors conclude that the denser among the clean fuels will be appropriate. That means ammonia or even methanol instead of hydrogen.
Two conversations, two very different views on future fuels. Given a further five conversations, there’s every chance I would encounter five more opinions, each with dramatic (and dramatically different) implications for the future shape of shipping. That means a lot of uncertainty, but as we consider the pathways to cleaner shipping, one thing remains the same. As always in shipping, the devil is in the detail.
Which fuels hold the most promise for decarbonising deepsea shipping? Send your thoughts to me at firstname.lastname@example.org to take part in the debate.