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How to monitor and measure ship exhaust?

Published on 10 June, 2024

Pollution and outdoor air quality,

Crucial to global trade and the movement of goods, shipping is also a major source of environmental pollution, affecting both water quality and the atmosphere.

The International Maritime Organisation estimates that the shipping industry is responsible for more than 3% of global anthropogenic carbon dioxide emissions and the IMO has therefore undertaken actions and strategies that include new regulatory measures on greenhouse gases.

Emissions from maritime transport and current legislation

As mentioned above, maritime transport is a major and growing source of greenhouse gas (GHG) emissions: carbon dioxide (CO2), nitrogen oxides (NOx), sulfur oxides (SOx), methane (CH4), particulates and soot.

In spite of this data, until less than a decade ago, this mode of transport was the only one not to be included in the European Union’s commitment to reduce greenhouse gas emissions.

In an effort to achieve the objectives of the Paris Agreement and climate neutrality by 2050, Regulation (EU) 2015/757 of the European Parliament and of the Council of 29 April 2015 on the monitoring, reporting and verification of carbon dioxide emissions from maritime transport was adopted.

It requires shipping operators to monitor and report emissions from their voyages to and from an EU port, including Iceland, Norway and Liechtenstein.

In the following years and under the European Green Pact, Regulation (EU) 2023/975 was drafted to amend Regulation 2015/757 in order to include shipping activities in the EU emissions trading scheme and to track, report and verify additional greenhouse gas emissions from different ships.

Who does the Ship Emissions Regulation apply to?

The regulation applies to all cargo and passenger ships of 5,000 gross tonnage (GT) or more and, from 2025, to general cargo ships of less than 5,000 GT (but not less than 400 GT) and ocean-going vessels of 400 GT or more.

Regarding the monitoring, reporting and verification (MRV system), the rules have so far applied to CO2, but from 2024 emissions of methane (CH4) and nitrous oxide (N2O) will also be included.

This Regulation applies to all ships arriving in, departing from or calling at ports under the jurisdiction of a Member State.

The inclusion of maritime transport in the EU ETS not only requires a monitoring plan to be verified and approved by the competent authority, but also requires the shipping company to pay for the corresponding emission allowances.

To ensure a smooth transition, shipping companies will be required to surrender a number of allowances equal to the total emissions generated during the calendar year, as follows:

  • 40% of reported verified emissions for 2024.
  • 70% of verified emissions for 2025
  • 100% of verified emissions for 2026 and subsequent years.


CTA Gas emissions


Methods for monitoring GHG emissions from ships

As mentioned above, the MRW System requires companies to record, collate, analyse and document comprehensive data on GHG emissions resulting from the combustion of fuels, both when ships are at sea and when they are at berth, to be reported to the competent authorities and verified by an external verifier.

According to the Regulation, the actual fuel consumption for each voyage will be used to determine emissions, which will be calculated using one of the following methods, at the choice of the company

  • Method A: fuel delivery notes and periodic tank checks.
  • Method B: on-board fuel tank monitoring.
  • Method C: flow meters for applicable combustion processes.
  • Method D: direct measurement of greenhouse gas emissions.

The monitoring and reporting report must include both the monitoring method used and its degree of uncertainty.

Direct measurement of GHG emissions

As the result of the emissions determination will directly influence the number of allowances to be surrendered, it is important that these calculations are as accurate and reliable as possible.

One of the valid methods for determining emissions is the ‘direct measurement method’, which is a continuous emissions monitoring system (CEMS) based on the use of accredited and calibrated instrumentation designed to provide highly reliable results for CO2, N2O and CH4 emissions from main engines, auxiliary engines, gas turbines, boilers and inert gas generators.

This instrumentation is designed to reduce errors and associated uncertainties compared to indirect measurement methods (Methods A, B and C) which have much higher uncertainty and error.

In this way, the use of CEMS to monitor emissions in maritime transport allows the performance of ships to be maximized with greater control of emissions rights.

At Envira, we are specialists in the integral management of CEMS projects, designing and implementing highly reliable systems for the determination of greenhouse gas emissions in maritime transport.

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