Low carbon maritime transport: How speed, size and slenderness amounts to substantial capital energy substitution

Three responses that reduce energy consumption and CO₂ emissions in maritime transport are slower speeds, larger vessels and slender hull designs. We use crude oil carriers as our illustrative example; these represent nearly a quarter of international sea cargo movements. We estimate the potential and costs in these which can all be described as capital substituting for energy and emissions. At different degrees of flexibility and time scales: Speed reductions are feasible immediately when there are vessels available, though more capital will be tied up in cargo. Deployment of larger and more slender vessels to a greater extent requires fleet renovation, and also investments in ports and infrastructure. A novel finding in our analysis is that if bunker costs rise as a result of emission costs (fees, quotas), then this may depress speeds and emissions more than if they result from higher oil prices. The reason is that for higher oil prices, more capital tied up in cargo may give cargo owners an interest in speeding up, partly counteracting the impulse from fuel costs that tends to slow vessels down. Emission costs, in contrast, do not raise cargo values.