Will the emission monitoring methods under the MRV Regulation remain as effective when data is kept in secret?

The Monitoring, Reporting and Verification (MRV) Regulation contains three emission monitoring methods which are generally praised for their transparency and effectiveness. This article examines these methods on their respective dis-/advantages and addresses the issues related to the proposed alignment of the MRV Regulation with the IMO Data Collection System (DCS).

1. Bunker Fuel Delivery Note (BDN) and periodic stocktakes of fuel tanks

How does it work?

This method is based on the quantity and type of fuel as defined on the BDN, combined with periodic stocktakes of fuel tanks based on tank readings. Tank tables relevant to each fuel tank are used to determine the volume at the time of the tank reading. The fuel consumed over the period (the time between two port calls) is comprised of the fuel at the beginning of the period, plus deliveries, minus fuel available at the end of the period and de-bunkered fuel between the beginning of the period and the end of the period.

What are the dis-/advantages?

This method is easily implemented on a global scale as it relies on the IMO legal framework and is already widely accepted and used where possible due to its simplicity. 

However, it cannot always be used, specifically when BDN is not available on-board. Additionally, the use of BDN can result in higher operational MRV costs, compared to the other methods, and its accuracy depends on the means and conditions under which the stocktakes are carried out. Moreover, it does not take into account any differences between the volume of fuel purchased and the actual volume of fuel consumed. 

2. Bunker fuel tank monitoring on board

How does it work?

This method works by taking daily fuel tank readings for all fuel tanks on-board, when the ship is at sea and bunkering or de-bunkering. The cumulative variations of the fuel tank levels between two readings are equal to the fuel consumed over the period.

What are the dis-/advantages?

Compared to the BDN Method, the benefit of fuel tank readings is that these readings already occur daily for purposes of stability and monitoring fuel consumption.  Additionally, fuel tank monitoring equipment is already installed on many ships. Furthermore, fuel flow meters produce the second lowest operational MRV costs, only after direct (continuous emission monitoring)  as they allow a higher degree of electronic monitoring and reporting.

As to disadvantages, the reliance of this method on fuel tank readings makes it more sensitive to inaccuracies, especially if fuel tank measurements are performed manually,  meaning that the accuracy of this method is limited to very inaccurate if performed manually. When done electronically the accuracy is higher. Finally, implementation of this method would entail the creation of a new IMO legal framework which could make it considerably more difficult.

3. Flow meters for applicable combustion processes

How does it work?

On-board flow meters determine the amount of fuel flowing through the respective pipes. It is measured directly (by volume, velocity or mass) or indirectly (by pressure).  The data from all flow meters linked to relevant CO2 emission sources is combined to determine the fuel consumption for a specific period.  A wide variety of flow meters is available, such as electronic, mechanical, optical and pressure based.

What are the dis-/advantages?

On the one side, fuel flow meters have the highest potential accuracy, compared to BDNs, tank monitoring, and direct emission monitoring, since it measures the actual fuel consumed in the fuel combustion system. Simultaneously, the accuracy depends on the flow-metering system, its installation, maintenance and calibration requirements and the competence of the on-board operator.  Because of the automated measurement, consistency and reporting are easier than with tank monitoring. Monitoring and reporting can also be made easier, more cost-efficient and more reliable than with BDNs and tank monitoring.

On the other side, same as with BDNs and tank monitoring, fuel consumption data will need to be linked to the relevant emission factors. The flow meters can vary widely in price, depending on the type of equipment installed. In addition, this method can be undermined if not all relevant flows are monitored, the flow meter could not continuously register fuel flows or if data is documented or reported falsely.  Finally, there is an increase in the relative through-life cost of the engine, with additional maintenance and calibration needed as well as a highly-trained on-board operator.

4. Direct CO2 Emissions Measurement Method

The fourth method under the MRV Regulation is equivalent to the On-board Continuous Emission Monitoring Method under the IMO NOx Technical Code. For more information on the method and its advantages and disadvantages, see our previous article here.


The MRV Regulation offers effective options for emission monitoring. However, there are currently talks to align the MRV Regulation methods with the IMO Data Collection System (DCS). The European Commission has asked for feedback on this proposal. A lot of stakeholders think that aligning the MRV Regulation with the DCS is not a good move since the DCS lacks transparency which in turn defeats the point of the MRV which aimed at being more transparent.

If you want to read the feedback provided by EMISA, click here.

What do you think?