1.3.2 Monitoring for accounting of emission certificates (ETS monitoring)

In contrast to HSE monitoring, concentrations of substances do not matter for monitoring according to the monitoring and Reporting Guidelines (MRG, COD 2010/345/EU) under the EU ETS Directive. From the ETS perspective, the economic impact is proportional to quantity of emitted CO2, i.e. the total mass of CO2 that has leaked into a water column or into the atmosphere has to be specified. In case of terrestrial leakage, CO2 flux densities (mass flux per time and area) are measured, e.g. in accumulation chambers. The total mass of CO2 emitted can be calculated by integration of repeated flux density measurements over time and area. The integration of a sufficient number of measurements is a challenge for monitoring, if the determination shall be within the limits of uncertainty stated in the guidelines for the monitoring and reporting of greenhouse gas emissions (mrg), i.e. ± 7.5%.

In principle, accumulation chambers can also be used for monitoring gas fluxes through lake beds or the sea floor. In the water column dissolved CO2 has to be taken into account in addition to a free CO2 phase. The reliable quantification of the total CO2 flux in an aquatic environment with reasonable effort is challenging. In consequence, the financial impact of CO2 leakage under water may be more severe as on land, because the uncertainties of CO2 quantification exceeding 7.5% will be added to the liability of the permit holder to return emission certificates equivalent to the remaining uncertainty of leakage quantification.