EU and Domestic Greenhouse Gas Emission Trading Systems - Continuous Sampling to determine the biogenic CO2 emissions

Overview on Emission Trading Systems

Over the last decade, there were several worldwide emission trading systems (ETSs) implemented as an instrument to fulfill the Paris agreement. Currently, worldwide, there are 28 ETSs and with that, the share of global emission covered by an ETS is 17%, which relates to 9 gigatons of CO2 equivalent (CO2e) [1].

In Europe, the EU-ETS (Emission Trading System) applies to power plants, industrial facilities, for e.g. cement kilns, iron and steel smelting, etc.
According to Directive 2023/959 [2] reason (98), the Commission will assess and report by 31st July 2026 on the possibility of including the municipal waste incineration sector in the ETS with a view to including it from 2028.
To be able to report the needed data in 2026, the European Commission published Directive 2023/2122 Monitoring and Reporting Rules (MRR) [3] which includes CO2 emissions from Waste to Energy (WtE) plants.
Beside this EU regulation there exist several domestic regulations, as e.g. in Germany the Fuel Emissions Trading Act (BEHG) in which waste incineration plants must participate since 1st January 2024 [4], in Italy UNI1607324 was published, which describes the determination of the renewable energy and can be used for emission trading and in UK, exists the Renewable Obligation (RO) scheme and the UK carbon emission tax.   
In all former mentioned regulations are listed different methods, how the total CO2 emissions and the biogenic fraction could be determined. The alternative methods are:
1.    No monitoring is carried out of either the waste or combustion gases to determine the proportion of biogenic CO2 emitted from the plant.
2.    Periodic waste sampling is carried out and the total biomass fraction is determined on the volume weighted biomass fraction of each waste group, which is multiplied by published factors.
3.    Application of the balance method, including standard ISO EN 18466
4.    A continuous measurement of the CO2 concentration and the exhaust gas volume flow in the exhaust gas duct to determine the total CO2 emission combined with a continuously sampling of the exhaust gas on an adsorber followed by a 14C analysis to determine the ratio of biogenic CO2 to fossil CO2 according to ISO EN 13833.  

Determination of the biogenic CO2 fraction

When waste or refused derived fuel (RDF) is burned, the various carbons are emitted into the atmosphere along with the CO2. Biogenic CO2 is defined as CO2 neutral and only the fossil CO2 portion of the emission is defined as a source of GHG.
One possible way for the determination of the biogenic fraction is the sampling of the flue gas on a CO2 adsorber followed by a 14C analysis, as it is described in ISO EN 13833. The 14C method uses the fact that the fossil and biogenic materials can be identified by a marker of the carbon atoms. The fossil material consists of 12C and biogenic material includes 14C.
The sampling method is described in EN ISO 13833 and can be explained with fig. 1.
The sampling system to determine the biogenic CO2 content extracts a part of the flue gas through a heated extraction probe (1) under volume-proportional conditions. A dust filter (2) is mounted at the probe entrance to prevent clogging of the probe and subsequent components. After the probe, the flue gas is sucked through a heated tube (3) to the control cabinet (4) and dried after entering the cabinet by cooling it in a gas cooler to approx. + 5 °C.
After the cooler, the dried flue gas is fed into an adsorber cartridge filled with a CO2 adsorber in which the CO2 contained in the flue gas is collected.
After the sampling period, the adsorber cartridge is sent to a laboratory and can be analyzed with Accelerated Mass Spectrometry (AMS), Liquid Scintillation Counter (LSC) or Beta Ionisation.
The AMESA B system was designed under the consideration of the minimum requirements of EN ISO 13833, to enable an automatic sampling of CO2 for sampling periods of several weeks. To ensure volume-proportional suction, a pitot tube is integrated into the sampling probe, or the signal of an existing stack flow device can be used as input. The sample flow rate is controlled by means of a mass flow controller.
After the sampling period of e.g. 1 month, the adsorber cartridge is replaced by a new one and the next sampling is restarted. In this way, it is possible to have a continuous sampling of the CO2 of the flue gas during the complete year. This method is like the continuous dioxin emission monitoring which is used for almost 30 years.

Applications and results

Over the last few years several projects were realized. One of these projects was the UIOM 14C project [5] - a cooperation project with the French environmental agency Ademe, fnade, Cabinet MERLIN and ENVEA.
During this project, CO2 samples were taken over a period of 12 months on a total of 10 MWI´s and one RDF plant. The AMESA B system was used to determine the biogenic proportion of CO2 emissions and the resulting share of renewable energy. The amount of waste incinerated in these plants corresponds to approximately 10% of the total amount of waste incinerated
in France.
With the help of the MASSBIO2 method developed by Cabinet Merlin, the biogenic and fossil mass fraction of the fuel and the share of renewable energy can be calculated based on the biogenic and fossil fraction of CO2 emissions.
The results of the analysis of 148 samples in the 10 MWI’s and 10 samples in the RDF plant are shown in Table 1.  
As seen in the table, the average biogenic CO2 fraction in the MWI´s is 67% and in the RDF plant is 78% which was higher than expected and published before.  
The results found in this project are also in line with the continuous monitoring of the biogenic CO2 fraction in a waste incineration plant for about 6 years. This facility is a waste incineration plant in a tourist area, which consists of two lines. In addition to household waste, sewage sludge is also partially incinerated here. Due to the strongly fluctuating number of people between the high season and the low season, strongly fluctuating amounts of waste are also generated. For this reason, not both lines are in permanent operation.
Figure 2 shows the biogenic CO2 fraction of the flue gas. Over the years, a repeating pattern can be observed with lower biogenic fractions in the summer months (green circles) and higher biogenic fractions in the winter months (red circles). The cause of this still needs to be investigated in more detail and may be related to poor waste separation with relating higher plastic content in the waste, during the high season periods.

4. Conclusions

With increasing numbers of Emission Trading Systems, the accurate determination of GHG emissions is getting more and more important. The implementation of waste incineration plants in national ETS-systems has already been realized in some countries and is discussed in the EU. Municipal solid waste and RDF is a quite inhomogeneous waste in comparison to coal or natural gas. Therefore, good, and easy methods are needed for this industrial sector to determine the total CO2 emissions of the plants.
Additionally, this fuel contains a significant portion of biomass. As in all ETS-systems the GHG credits are only needed for the fossil fraction of the CO2 emissions it’s very important to have easy and accurate methods to determine the biogenic CO2 fraction of the flue gas.
The results show that the current approach of assuming 50% of the CO2 emissions from waste incineration plants and RDF plants as biogenic can lead to an underestimation! In particular, the presented long-term measurements in a waste incineration plant show that the biogenic portion can be subject to considerable fluctuations over the course of the year.
The actual prices for 1 ton of CO2 vary in the different ETSs. Between 45.00 € in the German Fuel Trading act and around 100 € in the UK carbon tax regulation.  For example, this means that for a midsize EfW plant with a capacity of 100,000 tons per year relating to the emission of approx. 100,000 tons CO2 per year, that an uncertainty in the determination of only 1% of the biogenic fraction can lead to too high costs with variation of somewhere between 45,000.00 € and 100,000.00 €.
Such amounts stress the financial importance for an accurate determination of the biogenic CO2 emissions.
The AMESA B system has already demonstrated in several installations, including in the UK (e.g. Plymouth), that it is an easy and accurate way for the determination of the biogenic fraction of the CO2 emissions.  
   

References

[1] ICAP Status report 2023, https://icapcarbonaction.com/en/publications/emissions-trading-worldwide-2023-icap-status-report
[2] Directive 2023/959, https://eur-lex.europa.eu/eli/dir/2023/959/oj
[3] Directive 2023/2122, https://eur-lex.europa.eu/eli/reg_impl/2023/2122/oj
[4] https://www.gesetze-im-internet.de/behg/BEHG.pdf
[5] Determination of the biogenic and fossil contents of residual household waste and an SRF, based on a 14c analysis of the CO2 of post-combustion gases, Ademe, France, November 2020