Practical Options for Ship Emissions Monitoring

The EU has been on record for several years that it would take regional action to reduce greenhouse gas (GHG) emissions from ships, if no global agreement had been reached at the International Maritime Organisation (IMO) by the end of 2011. On 1 October 2012, European Commissioners Hedegaard and Kallas announced that the Commission would propose monitoring, reporting and verification (MRV) of emissions as a starting point towards a more comprehensive system to reduce emissions. Although a significant number of ship-owners are already voluntarily monitoring the efficiency of their fleet, there is currently no legal requirement in Europe for ship-owners to keep track of their vessels’ direct fuel consumption and communicate this data to port state authorities. The precise requirements to be contained in the EU MRV scheme are not yet known. The legislative proposal is not expected before the first quarter of 2013. This paper by Transport & Environment NGO highlights some important aspects to be taken into account when developing a reliable emissions monitoring system and it investigates different options.

2013.01.08 - Practical Options for Ship Emissions Monitoring Figure 1

An ideal ship emissions monitoring system such as the EU proposed MRV should be based on the following general principles:

  • Accuracy. The data collected should reflect as closely as possible the real emissions of the ship. Procedures for data collection and verification should follow clear and transparent guidelines in order to guarantee the highest level of data consistency. Last but not least, data should be certified and linked to the relevant instruments / documents used by port or flag state authorities to verify compliance and measure progress.
  • Enforceability. Enforcement is a crucial aspect to be taken into account when adopting the regulation. This point is all the more important if the MRV has to serve as a first step towards a regulation on CO2 reduction. Practical and robust enforcement can only be guaranteed if emissions data is easy to collect, survey and verify. Moreover, in order to minimise a ship’s delay in port and to ensure a minimal administrative burden (both for private operators and port state control), the procedure for data verification should be simple and rapid.
  • Transparency. The principle of transparency may sometimes conflict with the preservation of confidentiality, especially of “sensitive” information. However, together with data accessibility, transparency is a fundamental element to be respected in the establishment of the EU MRV system, especially if it has to serve as a cornerstone for a CO2 mitigation strategy. Transparency would lead to better decisions and could possibly improve energy efficiency in sector; e.g. by making the information on fuel consumption transparent, the charterers could take more informed decisions on what ship / company to charter. Public access to emissions data by ship is also important and should be guaranteed as a right: as is already the case for emissions from fixed installations covered by the ETS.

Different methods can be used to measure or estimate the CO2 emissions of a ship. Three of the four (non exhaustive) options that are presented here below are based on the measurement of fuel consumption, which has a direct relationship to CO2 emissions. So by establishing the carbon content of the fuel, the CO2 emissions can be calculated by applying an emission factor to fuel consumption data. The last option will rely on direct measurement of CO2 emissions (i.e. gas measurement) in the ship funnel. The options can be split into two categories:

Estimate options category based on activity data or written documentation and measurements made on board the ship. Estimate options could be defined as top-down and require a relatively high level of analytical work in order to provide emissions data. The estimate options category includes the following two measurement options:

  • Oil record book and bunker delivery notes. Current MARPOL regulations require ships to keep an oil record book, bunker delivery notes (BDN) and fuel samples on board and make them readily available for port state inspection. This material can, under certain circumstances, be used to determine fuel consumption and thus CO2 emissions. This approach uses fuel sold as a proxy for fuel consumption data and then emissions are calculated. While the method seems easily applicable to measure the amount of fuel sold (and then supposedly consumed) over a certain period globally, it is likely to be difficult to use to determine emissions during specific voyages. In addition, the accuracy of this method greatly depends on the quality and the exactitude of information contained on the BDN.
  • Estimating emissions from AIS data. The Automatic Identification System (AIS) was introduced by the IMO to enhance navigational safety by providing better information on ship location and the navigational status of vessels (e.g. at anchor, under way sailing, etc.). However, the system does not only collect data on location; it also includes static information on the vessel such as the ship’s IMO identification number, her name and dimensions as well as dynamic information on position at sea, course, speed over ground, etc. By correlating ship data (and thus information on the power installed on board, the type of engines, the type of fuel, etc.) with activity data, it is possible to estimate ship emissions. These estimates can be improved by calculating water resistance/friction, and information on currents and weather conditions etc. The main advantage of this option is that AIS data now has worldwide overage and is collected automatically for all ships for all journeys; the administrative burden for ship-owners is therefore reduced to a minimum. However, the verification and enforcement burden falling on public authorities / port state control is potentially very high. A lot of administration of data is required to estimate emissions with this option and the accuracy of the results will be highly dependent on the assumptions used (carbon content of the fuel, amount of power used, etc.) in the model.

Measurement options category that could be defined as bottom-up with no or very little data treatment required. The measurement options category includes the following two options:

  • Continuous fuel consumption monitoring. Monitoring fuel consumption can also be carried out on board and it has been widely used by ship owners and operators to assess operational and environmental performance of their fleet. On-board (continuous) fuel consumption monitoring can be done by using, for instance, fuel flow meters for the main and the auxiliary engines, by precise sounding of the tanks, etc. Different technologies have already been certified and are available for new builds and retrofits. Of course the accuracy of fuel measurements will be highly dependent on the type of equipment used, but modern systems have proven to be of high precision. Compared to the previous options, this method measures (and does not only estimate) the amount of fuel consumed. The accuracy of the results produced is therefore considerably enhanced. If a proper reporting system were to be established this data could easily be made available to public authorities. As the data collection is done automatically, the burden for the crew is minimized and because the data obtained is already in the form of fuel consumption figures, there will be no need for additional processing, which consequently reduces the burden for public authorities.
  • Direct emissions monitoring. A further approach would consist in directly measuring CO2 emissions in the funnel, without using fuel consumption figures as a proxy. This option is fundamentally different from the previous ones as it relies on the measurement of gas (i.e. CO2) and not liquid (fuel). On board exhaust gas measurement is already available and is used by a number of shipping companies. Similar to on-board continuous fuel consumption monitoring, direct emissions monitoring seems to be an attractive option to provide robust and transparent data both for the operators and for automatic reporting to enforcement authorities. The main advantage of direct monitoring is the ability to combine CO2 measurement with other air pollutants such as SOx and NOx. As a result this method could be used as a unique instrument for the measurement of all ships’ emissions to air and to inform the regulator, as an enforcement tool and as a performance indicator etc.

A comparison of the above mentioned monitoring options is presented in the following table:

2013.01.08 - Practical Options for Ship Emissions Monitoring Figure 2

Source: Transport & Environment


  1. Effective treaties depend on a number of factors including monitoring for both enforcement and observational data. A key to this is verification.
    Most Multilateral Environmental agreements include some form of CEMS.
    However, ratification of MARPOl was proving difficult and in the end the method adopted was two steps back from the ideal and subject to a complete absence of verification and of insufficient detail to be valuable for observational data.

    Ideal would be exhaust gas monitoring of COX< NOX and SOX.
    Expensive and impracticable at the time.
    They therefore considered indirect monitoring. But here again problems.
    Indirect would mean using the mass flow of fuel and the engine paramters for COX and NOX and fuel sulphur for SOX (the origin of SOX is sulphur in the fuel).

    In theory this is quite workable but it was felt that inline density measurement (no problem with that) and inline sulphur measurement coupled with fuel flow meter readings could provide SOX measurements.
    The idea was that all the data would be automatically collected and reported in real time via the AIS system. This could also use the mass flow and the engine rpm and certification to real time log and report all emmissions.
    However, online sulphur analysers (x-ray fluorescense) were considered very expensive and required ongoing skill maintenance and calibration.

    So a further step back to using the density and sulphur reported in the fuel analysis with the fuel flow would be an acceptable alternative. Unfortunately, this assumes that once analysed, a fuel's quality will remain unchanged (even if correctly analysed to begin with) and this also assumes that the fuel is, as ISO 8217 requires, homogeneous which, at least for density viscosity and sulphur, it often is not. In realitu fuel quality is very variable, the fuels often far from homogeneous and often consolidations of different fuels each inaccurately analysed or compromised subsequent to analysis.

    One test house reported that commercial samples analysed showed significant differences in density between the commercial sample and the original BDN or CQ in over 50% of cases for HFO and over 35% of cases for MGO/MDO.

    The drip sample often hides more than it reveals which is often merely and average of the properties of the whole bunker.

    Then too it was felt that because of the financial advantages of fraud, and the ease with which samples and records could be falsified that there was "every likely-hood of vessels being non-compliant".

    Of course, there are ways to make this system work and by which it would be possible to automate data collection just as with any other instrumented approach. The key to instrumentation and automation being that the human factor can be eliminated and the data could be verifiable. However, sulphur analysers requiring ongoing maintenance and calibration by skilled personel means that the sensor can be made to say what the operator wants it to say but it also is a retrograde step because what vessels are working toward is demanning and deskilling and the unmanned engine room environment.
    SO any instruments must be free from the needs of calibration and maintenance and thus capable of being made tamperproof.

    Razaghi Meyer came up with the integrity system as a solution within the original MARPOL reporting scheme and utilising much of the already necessary equipment but in the face of the industries lack of interest in fuel quality, except where it affects value and which can be resolved via dispute resolution and because to address fuel quality and fuel management issues would impose a severe cost burden likely to push up fuel prices still further, we are left with the same fuel quality issues as ever.

    Of course, once a system of continuous emmissions monitoring and real time reprting comes into force, vessels will have to finally address fuel quality problems. This is because the CEMS acts like a speed camera. One infringement and you are in violation and subject to penalties. This could happen if the fuel is not homogeneous and a high sulphur portion happens to flow at a time when the vessel is within an ECA.

    Unless, that is, the legislators will take a more relaxed view whcih says averegaed values are OK. This is a difficult question where much of this legilsation and enforcement is being driven by unrealistic eco activist NGOs.

    For information of the monitoring issues see the MARTOB reports on Bilge water and fuel sulphur and the NERA reports on Market based mechanisms both of which comment on the long recognised eed for some work to be done on verification and enforcement.

  2. PS a limitation of MARPOL’s current method is that it relies on manual logging of data at infreguent intervals. In the 24 hours between fuel meter readinsg the vessel can travela significant distance.
    Automated data collection means that the emissions can be traced to comparatively small sea areas which means much more useful observational data. If verifiable. And once automated it can be harvested by wi fi whene evr a vessel enters habour.

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