Sulphur abatement globally in maritime shipping

In 2016, the International Maritime Organization (IMO) decided on global regulations to reduce sulphur emissions to air from maritime shipping starting 2020. The regulation implies that ships can continue to use residual fuels with a high sulphur content, such as heavy fuel oil (HFO), if they employ scrubbers to desulphurise the exhaust gases. Alternatively, they can use fuels with less than 0.5% sulphur, such as desulphurised HFO, distillates (diesel) or liquefied natural gas (LNG). The options of lighter fuels and desulphurisation entail costs, including higher energy consumption at refineries, and the present study identifies and compares compliance options as a function of ship type and operational patterns.The results indicate distillates as an attractive option for smaller vessels, while scrubbers will be an attractive option for larger vessels. For all vessels, apart from the largest fuel consumers, residual fuels desulphurised to less than 0.5% sulphur are also a competing abatement option. Moreover, we analyse the interaction between global SO_X reductions and CO₂ (and fuel consumption), and the results indicate that the higher fuel cost for distillates will motivate shippers to lower speeds, which will offset the increased CO₂ emissions at the refineries. Scrubbers, in contrast, will raise speeds and CO₂ emissions.     

Environmental regulations in shipping: Policies leaning towards globalization of scrubbers deserve scrutiny

Emission regulations for Sulphur oxides (SOx) and nitrogen oxides (NOx) are motivated by health- and other environmental objectives in local and regional settings, while global warming concerns motivate policies for carbon dioxide (CO₂). We point out that the direction chosen by the International Maritime Organization (IMO) – to tighten SOx and NOx limits globally – carries important risks. First, extending to a global setting the present regulations in coastal emission control areas (ECAs, in North America and Northern Europe) gives negligible or negative environmental benefits, and raises global warming impacts. Second, ‘end-of-pipe’ solutions, such as scrubbing and tuning, become dominant responses, and they reduce energy efficiency. Third, the adoption of these end-of-pipe solutions carry risks of deflecting attention from development of cleaner fuels and improving energy efficiency. Distinguishing local environmental benefits from global ones is important in general, and our research concludes that in the case of shipping, this distinction better serves the needs of the local environment, the global climate, and conserves on abatement costs.     

On two speed optimization problems for ships that sail in and out of emission control areas

This paper deals with two speed optimization problems for ships that sail in and out of Emission Control Areas (ECAs) with strict limits on sulfur emissions. For ships crossing in and out of ECAs, such as deep-sea vessels, one of the common options for complying with these limits is to burn heavy fuel oil (HFO) outside the ECA and switch to low-sulfur fuel such as marine gas oil (MGO) inside the ECA. As the prices of these two fuels are generally very different, so may be the speeds that the ship will sail at outside and inside the ECA. The first optimization problem examined by the paper considers an extension of the model of Ronen (1982) in which ship speeds both inside and outside the ECA are optimized. The second problem is called the ECA refraction problem, due to its conceptual similarity with the refraction problem when light travels across two different media, and also involves optimizing the point at which the ship crosses the ECA boundary. In both cases the objective of the problem is to maximize daily profit. In addition to mathematical formulations, examples and sensitivity analyses are presented for both problems.     

Real-time route diversion control in a model predictive control framework with multiple objectives: Traffic efficiency,emission reduction and fuel economy

In this paper, the route recommendation provided by the traffic management authority, rather than the uncontrollable bifurcation splitting rate, is directly considered as the control variable in the route guidance system; a real-time en-route diversion control strategy with multiple objectives is designed in a Model Predictive Control (MPC) framework with regard to system uncertainties and disturbances. The objectives include not only traffic efficiency, but also emission reduction and fuel economy, which respectively correspond to minimizing the total time spent (TTS), total amount of emissions and fuel consumption for all vehicles moving through a network. In the MPC framework, the routing control problem is transformed to be a constrained combinational optimization, which is solved by the parallel Tabu Search algorithm. Two representative traffic scenarios are tested, and the simulation results show: (1) The room for improvement in each objective by means of route diversion control is not consistent with each other and varies with the utilized traffic scenario. In the peak hour, the routing control can lead to significant improvements in TTS and fuel economy, while a relatively small improvement in emission reduction is achieved; in the off-peak hour, however, it is opposite, which indicates that routing is possibly dispensable from the aspect of improving traffic efficiency, but is required from the aspect of emission reduction. (2) The conflict among the multiple objectives varies with the utilized traffic scenario in route diversion control. Improving traffic efficiency often conflicts with emission reduction in both scenarios. For the objectives of traffic efficiency and fuel economy, they are not conflicting in peak hour, while in the off-peak hour, the two objectives are likely conflicting, and the improvement in one objective can lead to the degradation in the other objective. (3) Regardless of the scenarios of peak hour or off-peak hour, the proposed control strategy can result in a proper trade-off among the three chosen objectives.     

The costs and benefits of a nitrogen emission control area in the Baltic and North Seas

The main purpose of this paper is to analyse the socio-economic justification of implementing a Nitrogen Emission Control Area (NECA), starting 2021, for ships in the Baltic Sea and/or the North Sea and English Channel. We analyse the potential for emission reduction, emission control costs, and monetised benefits following the introduction of a NECA. Costs and benefits are compared for 2030. We compile new data on emission control costs for shipping, use the GAINS model for calculations of emission dispersion, and the Alpha-RiskPoll model for estimating monetary values of health impacts. The model results show that costs to conform to the NO_X regulations of a NECA in the Baltic Sea, North Sea or both sea regions would be 111 (100–123), 181 (157–209), and 230 (195–273) million € per year, respectively. Corresponding benefits from reduced emissions are estimated to be 139 (56–294), 869 (335–1882), and 1007 (392–2177) million € per year, respectively. Calculated benefits surpass costs for most scenarios, but less convincingly for a Baltic Sea NECA. Conforming to the NECA regulations by using Liquefied Natural Gas (LNG) propulsion engines is estimated to give the highest net benefits but also the largest variation (costs: 153 (88–238), benefits: 1556 (49–3795) million €/year). The variations are mainly due to uncertainties in the valuation of avoided fatalities and climate impacts. It is concluded that the NECAs for the Baltic and North Seas can be justified using CBA under all but extreme assumptions.