Abstract
Maritime shipping is a strategic sector with a strong international vocation and management. The need to define regulations valid for many different countries without generating disparities of treatment slowed down the formulation of environmental regulations, especially for atmospheric emissions. In particular, regulations pertaining to the reduction of sulphur compounds allowed two distinct approaches: the use of low-sulphur fuels or exhaust gas cleaning systems, the so-called Scrubbers. The actual implementation of these solutions presents specific concerns either related to the toxicity of atmospheric by-products and to the fuel cost or to the generation of polluting washwaters that may need treatment before discharge. In this paper we analyzed the potential environmental benefit deriving from the use of a distillate fuel, not compliant with current IMO Sulphur Regulations, together with a Scrubber. The pilot-scale experimental results indicated that a limited amount of water and/or scrubber volume is needed to reduce sulphur emissions below regulations on maritime shipping, especially with the addition of NaOH reaching a water-saving between 25%-33% compared to the use of pure seawater. Experiments indicated that scrubber washwater PAHs emissions are within the available water quality standards indicated by EU and USA guidelines. A bottom-up analysis on heavy metals concentration shed light on the prominent role of metal-parts corrosion on the washwater emissions. Taking into account for corrosion phenomena, the actual heavy metals concentration in the washwater deriving from scrubbing was normally below the water quality standards.
Highlights
Due to the progressive introduction of severe regulations regarding the maximum allowed sulphur content in fuels for on-road vehicles and on the emissions of S O2 in industrial productions and power plants, the emission of SO2 in the atmosphere is progressively decreasing since more than 50 years
In order to achieve a reduction of sulphur emissions while preserving the overall economic balances of shipping companies and fuel availability, the MARPOL VI introduced two options to guarantee compliance to their emission targets: 1) to control the sulphur content in the fuel or; 2) to adopt exhaust gas cleaning systems to depurate the gas before they enter the atmosphere
The same MARPOL identified some sulphur Emission Control Areas (SECA) within which the equivalent sulphur content is lowered to 0.1% in weight
Summary
Due to the progressive introduction of severe regulations regarding the maximum allowed sulphur content in fuels for on-road vehicles and on the emissions of S O2 in industrial productions and power plants, the emission of SO2 in the atmosphere is progressively decreasing since more than 50 years. Notwithstanding their better properties, not all distillate fuels are able to comply with regulations on sulphur content and the toxicity of the particles they produce in the marine engines appeared even larger than those produced by residual fuels (Wichmann 2007; Schmid et al 2009; Di Natale and Carotenuto 2015; Oeder et al 2015; Reis et al 2018; Liu et al 2019) In this sense, the use of scrubbers, with their capacity to remove sulphur compounds and partially capture. This paper proposes a possible option to reduce ships’ environmental footprint both in terms of air and water impact by using a distillate fuel in combination with a marine scrubber This kind of fuel can be used in most of the existing engines and are largely available on the market. The results are compared with the global and the SECA limits on sulphur emissions imposed by the IMO and with the limits imposed on PAH and heavy metals for land-based installation and with the indication for Natural Waters Quality Standards imposed by several countries
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