Reducing atmospheric emissions from marine shipping

Carrying as much as 90 per cent 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 eight billion tonnes of cargo being transported across the globe annually will soar to 23 billion tonnes per year in the next 50 years. However, with the increasing volumes of cargo being transported annually, rising levels of marine emissions such as sulfur oxides (SOx), oxides of nitrogen (NOx), particulate matter (PM) and carbon dioxide (CO2) from the fuel used to power these vessels, are under close scrutiny by world environmental authorities.

While the global shipping industry is currently responsible for only three per cent of greenhouse gases, this contribution has prompted significant changes in the legislated control of emissions. A key concern is the heath of communities living inclose proximity to shipping lanes.

One of the busiest maritime routes revolves around the area entering in, and departing out of, Hamburg in Northern Germany. Almost 80,000 ships call into European ports each year, adding significantly to air pollution due to high sulfur and the heavy bunker fuels burnt at sea and also at dockside. Hamburg is Europe’s largest container port after Rotterdam and citizens there are in support of urgent action to reduce the sulfur emissions limit.

Another prime example is that of the 30 km Bosphorus Strait in Turkey, one of the most highly trafficked shipping channels in the world. Only 3.6 km wide at its broadest section and less than one km at its narrowest, the Bosphorus flows directly through the city of Istanbul, which has a population of some 15 million people. On average, 140 international trade vessels, including oil tankers, pass through the Straits every day. Owing to strong currents in this channel, shipsmust use their engines on high power which can lead to a significant issue regarding shipping emissions and its environmental impact on the city. Maritime traffic on the Bosphorous is increasing and exhaust emissions (NOx, CO2, VOCs and PMs) from international shipping, as well as vehicle and passenger transit vessels which cross the Straits daily and account for up to three hundred ferries a day – are posing a health and general environmental hazard to the city’s inhabitants. This potential human health issue has led to the Turkish government investigating the opening of a new open water channel to advance Mediterranean trade before the problem increases in severity. And clearly, emissions control is another possible mitigation.

For environmental reasons Liquefied Natural Gas (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. And, there is also a growing trend for automotive sector NOx 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, NOx and PM pollutant emissions are reduced through the use of wet gas scrubbing for SO2 removal, reaction of SO2 with lime, reaction of NOx with ammonia in SCR and 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 sophisticated, but the trend is going in a similar direction and is being driven by phased implementation of environmental protection legislation through MARPOL.

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 International Maritime Organization (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 who have signed up to the MARPOL legislation represent 98 per cent 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 NOx, SO2 and PM 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 United States Caribbean Sea ECA, covering certain waters adjacent to the coasts of Puerto Rico and the United States Virgin Islands, took effect from January 2014. Further ECAs seem likely to be proposed for Norway and Japan, and possibly for the Mediterranean and Black Seas and the seas around Mexico, Korea and, potentially also 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 for each one. 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 SOx emissions in ECAs saw the allowable amount of fuel sulfur reduced to from 1.5 per cent to 1.0 per cent in July 2010 and this was further lowered to 0.1 per cent in January 2015. Outside of ECAs, the current global limit of3.5 per cent sulfur-in-fuel was reduced from 4.5 per cent to 3.5 per cent in January 2012, and is likely to be further reduced below 0.5 per cent in 2020 or 2025 depending on a review in 2018 to determine the availability of fuel to enable implementation of this standard.

In terms of NOx, an inevitable by-product 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 per cent reduction in NOx 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 selective catalytic reduction (SCR), that can either be used continuously whilst at sea, or can be activated only when entering the ECAs and thereby reducing commercial shipping & international trade operating costs.

A proposal was published in June 2013 (no. 525/2013) by the European Commission to regulate CO2 emissions emanating from the shipping industry. The proposal aimed to reduce GHG (Green House Gases) emissions by 2015 to levels 50 per cent lower than those in 1990 through the establishment of a European MRV (Monitor-Report-Verify) system. The MRV system can either be based on the calculation of fuel consumption or stack monitoring. In case of the latter, a monitoring plan is to be submitted to the authorised verifiers no later than August 2017.

Little can be done to reduce the CO2 produced by the combustion processes, but there are certainly proven and cost effective methods to reduce NOx, SOx (mainly sulfur dioxide) and PM present in the emission stream. Mitigation measures focus on process control and management and detection of post-combustion emissions, to both protect the health and safety of the people on board the ship, and also to reduce environmental impact. DeNOx technology can be retrofitted to the system to reduce NOx, while an interesting method of removing SOx emissions is the use of seawater for wet scrubbing. No additives are required in this method, as the inherent alkalinity of the seawater is used as the sorbent, and no by-products are produced beyond a slight increase in the natural concentration of sulphate in seawater.

In order to comply with the ever-tightening emission regulations, shipping operators might choose to adopt an integrated approach that considers the use of lower sulfur content fuel, the use of wet-gas scrubbing for SO2 removal, the use of SCR for NOx reduction or a conversion to LNG. However, this last option would require technology adjustments, similar to the engine retrofits currently being applied in the automotive industry.

Other emission management measures called for by the legislation include implementing a far higher level of measurement, analysis and reporting during voyages. Emissions such as oxygen and carbon monoxide levels in the combustion process can be monitored to ensure that the process is functioning optimally. It is also possible to measure different hydrocarbons such as methane, propane, butane, isobutane and pentane to determine if fuel is escaping from the engine. Hydrogen sulphide is also often measured and controlled at various different points in the reaction pathway. Urea and ammonia levels also require monitoring to make sure the DeNOx equipment is working well and that the ammonia or urea is not being overdosed, which would result in the undesirable, so called, ammonia ‘slip’.

The tightening legislation also impacts players beyond the shipping industry, notably the designers and manufacturers of marine diesel engines, and the associated emission reduction technologies, as well as the refineries implementing sulfur reduction technology to produce lower sulfur bunker fuels for shipping. This low sulfur fuel introduction also impacts the bunker fuel oil stocking locations in the supply chain that hold inventory for ships. As part of this ‘shore to ship’ emissions reduction scenario, Linde also works closely with refineries to supply gases such as oxygen and hydrogen and implement technology to reduce sulfur levels at these refineries. Oxygen enrichment technology has come to the fore as a viable and a cost-effective solution for significantly increasing a refinery’s sulfur handling capacity, as well as addressing problems associated with contaminants such as ammonia and hydrocarbons. In addition, analysis of sulfur compounds at a refinery has become a critical requirement and there are several different techniques available to accomplish this. In addition to continuous emission monitoring systems (CEMS), there is also gas chromatography and other instrumentation used in a laboratory, as well as specific hand held gas detectors which are sensitive to sulfur or sulfur compounds. These technologies are able to measure from very low levels — parts per billion — up to percentage levels, depending on what kind of instrumentation or detector involved. High purity gases and calibration gas mixtures from the Linde HiQ specialty gases product ranges are essential for the daily operation and periodic calibration or functional testing of these sulfur measurement instruments.

Linde Gases supports the global shipping industry and its associated supply industries with state-of-the art emissions management and mitigation technologies. A key area is the supply of high precision HiQ specialty gases calibration gas mixtures to the facilities where emissions testing of heavy marine engines is carried out during their development or production, to ensure compliance with emissions regulations. This sector requires accurate calibration of the test instrumentation that detects and monitors emissions volume and type. Under the brand name HiQ®, Linde offers a number of highly tailored calibration gas mixtures and pure specialty gas grades up to 99.99999 per cent purity to ensure consistently accurate analytical measurement. This portfolio of products is continually evolving to remain relevant to the needs of the industry, for example, as the MARPOL legislation evolves.

With LNG now being seriously evaluated as an alternative marine fuel, Linde has already developed the necessary technology to supply the maritime industry with this efficient and environmentally friendly replacement for bunker oil. The use of LNG allows for a significant reduction in SOx, NOx and CO2 emissions, offering ship owners and operators a sustainable solution to meet existing and future emission standards. Other significant advantages are a very low safety risk and the possibility of combining LNG with other fuels in a dual-fuel engine. Linde is one of the few companies in the world able to deliver a complete solution for LNG. From liquefaction and the safe and reliable delivery, handling and storage of cryogenic liquids to bunkering, vaporising and dispensing, Linde provides an end-to-end solution for customers looking to reduce fuel costs and environmental impacts.

In a landmark agreement, the shipping company EMS AG and Bomin Linde LNG, a full-service provider of LNG as fuel for the marine market, recently signed the first contract for the delivery of LNG to Germany. The agreement is seeing the supply of LNG as fuel for the MS Ostfriesland passenger ferry operated by AG EMS, following a retrofit, making it the first user of LNG for German passenger ferry services. Regarded as an important step towards using LNG as a marine fuel in Germany, the agreement sends a clear signal that this low-emission propulsion system will play an increasingly important role in the marine sector in future years.

The technical process for storage of LNG is comparable to bunkering operations for traditional fuels, but since the LNG is cooled down to approximately -163oC, appropriate personnel training is required. Deliveries to the port of Emden are currently covering initial supply requirements, while two LNG bunker terminals are being constructed in the ports of Hamburg and Bremerhaven. Once operational in 2015, these terminals will be able to supply LNG to ships operating in German ports along the North and Baltic Seas.