Mountain high, ocean deep: part one

Carrying as much as 90% of world trade, the international shipping industry is crucial to the intercontinental trade activities that underpin the global economy. It has been estimated that if the growth of the past 150 years continues, the current 8 billion t of cargo being transported across the globe annually will soar to 23 billion tpy in the next 50 years. However, with the increasing volumes of cargo being transported annually, rising levels of marine emissions are under close scrutiny by world environmental authorities.

Ocean shipping can generally be divided into two cargo submarkets: bulk or crude/refined petroleum products and dry cargo. Bulk goods comprise iron ore, coal, grain, phosphates and bauxite, as well as non-ferrous metal ores, feed and fertilisers. However, crude oil is the big player worldwide, accounting for approximately 25% of all goods transported by sea.

While the global shipping industry is responsible for only 3% of greenhouse gases, this contribution has recently prompted significant changes in the legislated control of emissions from this sector. A key concern is the health of communities living in close proximity to major ports and shipping lanes.

For environmental reasons, LNG and even wind propulsion and nuclear power are occasionally employed to propel commercial shipping, but the majority still use a reciprocating diesel engine as their prime mover, powered by fuel oil, also known as bunker oil. Combustion of bunker oil in ships generates the same pollution components as those emitted from road transport vehicles and is similar to the emissions footprint from other fossil fuel burning industries such as electrical power plants. However, most of the sulfur emissions from land based transport are eliminated by the use of low sulfur fuels, where the sulfur is removed at the refinery. There is also a growing trend for automotive sector NO_X emissions to be reduced using selective catalytic reduction (SCR) with the addition of urea as a source of ammonia. In the power generation industry, SO₂, NO_X and PM pollutant emissions are reduced through the use of wet gas scrubbing for SO₂ removal, by reaction of SO2 with lime, reaction of NO_X with ammonia in SCR and selective non-catalytic reduction (SNCR) technologies and electrostatic precipitation for PM reduction. These techniques are highly effective in cleaning the flue gas from the power plants. By comparison, the control of these emissions from shipping has historically been less rigorous, but the trend is going in a similar direction and is being driven by phased implementation of environmental protection legislation through the International Maritime Organization (IMO) and MARPOL.

Shipping takes its turn in the legislative queue

Marine pollution is regulated internationally and one of the key international conventions for the prevention of pollution at sea is MARPOL 73/78, adopted by the IMO in 1973, and later updated in 1978 after several severe tanker accidents. The convention includes regulations aimed at preventing and reducing pollution at sea from ships, including both accidental pollution and pollution from routine operations. Today, countries that have signed up to the MARPOL legislation represent 98% of international shipping.

This convention has seen the designation of special so called emission control areas (ECAs) where stricter controls on the principal marine emissions NO_X and SO₂ have been put in place. These ECAs are generally designated in densely populated areas close to high levels of shipping and their regulations are also cascaded into regional and local legislation through regional authorities such as the European Union.

Following agreement at the IMO and incorporation into European law, the Baltic Sea became the first fully implemented ECA in August 2006, followed a year later by the designation of the North Sea and English Channel as the second ECA. In August 2012, new ECAs were designated for ships trading off the coasts of Canada, the USA and the French overseas collectivity of Saint-Pierre and Miquelon. A new area, the US Caribbean Sea ECA, covering certain waters adjacent to the coasts of Puerto Rico and the US Virgin Islands, took effect from January 2014. Further ECAs seem likely to be proposed for Norway and Japan, possibly for the Mediterranean and Black Seas and the seas around Mexico, Korea, and potentially the heavily used Malacca Strait.

The issue of designating the Malacca Strait as an ECA is the subject of frequent debate, since the diversity and scale of shipping activities in this area is massive and it would be extremely challenging to monitor and enforce the emission regulations. Effectively, this inclusion would mean regulating most of the world’s shipping operators. Whilst this might be highly desirable from an environmental perspective, it would also be highly complex.

A phased reduction of SO_X emissions in ECAs saw the allowable amount of fuel sulfur reduced to from 1.5% to 1.0% in July 2010 and this has been further lowered to 0.1% in January 2015. Outside of ECAs, the current global limit of 3.5% sulfur in fuel was reduced from 4.5% to 3.5% in January 2012, and is likely to be further reduced to 0.5% in 2020.

In terms of NO_X, an inevitable byproduct of combustion of fuel with air, January 2016 is expected to herald the stringent IMO Tier III emission limits for ships constructed after January 2016 operating within the North American and US Caribbean Sea ECAs. The Tier III standard represents a 75% reduction in NO_X emissions compared to current Tier II engines and is valid for marine diesel engines with an output of more than 130 kW power. Although it remains technology neutral, the IMO regulation assumes that these standards will be met through the application of abatement technologies, such as SCR, that can either be used continuously whilst at sea, or can be activated only when entering the ECAs and thereby reducing commercial shipping and international trade operating costs.

A proposal was published June 2013 (no. 525/2013) by the European Commission in order to regulate CO₂ emissions from the maritime industry. The proposal aims to reduce greenhouse gases (GHG) emissions by 2050 to levels 50% lower prior to 1990 by establishing a European monitor report verify (MRV) system. This MRV system can be based either on the calculation of fuel consumption or stack monitoring. In case of the latter, a monitoring plan needs to be submitted to the authorised verifiers at the latest by August 2017, before the start date of monitoring, 1 January 2018.

Little can be done to reduce the CO₂ produced by the combustion processes at sea, but there are certainly proven and cost effective methods to reduce NO_X and SO_X (mainly sulfur dioxide) present in the emission stream. Mitigation measures focus on process control and management and detection of post combustion emissions.

Read part two of this article here.

Written by Stephen Harrison and Ismail Erilhan, Linde Gases. This is an abridged version of an article taken from Hydrocarbon Engineering’s August 2015 issue.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/31072015/mountain-high-ocean-deep-part-one-1205/