> For the complete documentation index, see [llms.txt](https://docs.rainbowstandard.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rainbowstandard.io/methodologies/biogenic-carbon-capture-and-storage-bioccs/sampling-and-measurements.md).
# Sampling and measurements
🇪🇺 CRCF requirement: Measurements of CO2 stream
In addition to following the requirements set out in this section, CRCF projects shall ensure measurements of the CO2 stream are taken in accordance with Articles 40-46 and Article 49 of the [European Commission's Implementing Regulation 2018/2066](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A02018R2066-20250527#anx_IV).
### **Measurement standards**
All measurements of the CO2 stream shall be carried out using methods based on
* EN 14181: stationary source emissions - quality assurance of automated measuring systems
* EN 15259: air quality - measurement for stationary emission sources - requirements for measurement sections and sites and for the measurement objective, plan and report
* other relevant EN standards, in particular EN ISO 16811-2: stationary source emissions - manual and automatic determination of velocity and volume flow rate in ducts
Where none of the above is available, methods shall be based on suitable ISO standards, national standards, industry best practice guidelines or scientifically proven methodologies.
Laboratories carrying out measurements, calibration and equipment assessment for the measurement system shall have at least one quality assurance accreditation for the relevant analytical methods or calibration activities, such as:
* ISO/IEC 17025
* CEN/TS 17225-1
* ISO 10694
### **Calibration requirements**
Measurement systems shall be:
* **Calibrated, adjusted, and checked at regular intervals**, including prior to entering service, at an accredited calibration facility or laboratory traceable to recognized international or national measurement standards.
* **Installed in accordance** with international or national standards or the manufacturer's specifications.
* **Recalibrated periodically**, at least annually, meeting or exceeding international or national standards (e.g. EN 14181 in the EU) or manufacturer's specifications, including parallel measurements against standard reference methods carried out by competent staff.
Where a component of a measurement system cannot be calibrated, Project Developers shall identify this in the monitoring plan and propose an alternative control method.
Where equipment is found to be non-compliant with performance requirements, Project Developers shall take corrective action without undue delay.
### **Determination of the amount of CO****2**
The amount of CO2 at each [measurement point](#user-content-fn-1)[^1] shall be determined using **direct measurements** (i.e. physical measurement equipment) rather than a calculation-based approach. Measurements shall meet a maximum measurement uncertainty of **±2.5%**, meaning the uncertainty across all measured parameters.
The amount of CO2 shall be calculated by continuously measuring the CO2 concentration and the mass or volume flow rate, and multiplying them. For each measured parameter listed below, **hourly averages** shall be calculated using all data points available within that hour. Raw measurements data shall be made available upon request by Rainbow or the VVB.
Where equipment is temporarily out of operation during part of an hour, the hourly average may still be calculated from the remaining data points, provided at least **80% of the expected readings** for that hour are available. If fewer than 80% are available, the requirements in the [Handling missing data](#handling-missing-data) section below apply.
The following requirements for the measurement of the CO2 stream parameters apply:
#### **Mass or volumetric flow of the stream,** $$m\_{stream}$$ **or** $$V\_{stream}$$
The mass or volumetric flow of the CO2 stream shall be measured
* **continuously**, at least every 15 minutes, and **aggregated over one day.**
* before leaving the capture site, when being transferred to a new transport segment, before entering the storage site, and/or at the last monitoring point before entering permanent storage, depending on whether the [segregated](/methodologies/biogenic-carbon-capture-and-storage-bioccs/ghg-quantification.md#segregated-stream) or the [non-segregated stream](/methodologies/biogenic-carbon-capture-and-storage-bioccs/ghg-quantification.md#non-segregated-stream) approach applies.
* using a mass or volumetric flow meter. Project Developer shall prioritize metering technologies that are [widely used ](#user-content-fn-2)[^2] in CCS measurements, such as differential pressure meters (orifice plate meters), turbine meters and coriolis meter.
Flow meters shall be chosen according to the conditions and ranges under which it will operate.
#### Density of the stream, $$\rho\_{stream}$$
The amount of CO2 is reported in tonnes of CO2, a mass unit. To convert volume to mass flow, the stream's density is required.
The density shall be measured either by using an in-line densitometer[^3] or similar devices, or modeled using an **equation of state (EoS)**. To model density from the EoS, the selection of an appropriate model, knowledge of the stream composition and reference pressure and temperature measurements are crucial. Various approaches for density determination using EoS can be found in the[ literature](#user-content-fn-4)[^4].
Measurements of the density shall be conducted
* **continuously**, and at the same frequency as the flow metering,
* as close to the metering point as possible.
Densitometers shall be calibrated with relevant reference fluids.
#### Pressure and temperature of the stream, $$p,T$$
Volumetric flow and density measurements are recorded at operational pressure and temperature but shall be converted to **standard temperature and pressure conditions, STP.**
Measurements of the operational pressure and temperature shall be conducted
* **continuously**, at the same frequency as the flow metering. Raw measurements data shall be made available upon request by Rainbow or the VVB.
* as close to the metering point as possible
* using pressure and temperature meters (e.g., pressure transducers, thermocouples, thermistors)
#### Concentration of CO2 in the stream, $$F\_{mass,\ CO2}$$
​The CO2 concentration is measured either by direct measurement of the CO2 concentration in the stream, or by indirect measurement of the chemical composition (i.e. CO2 and impurities) of the stream. The CO2 concentration using either of the two methods shall be measured
* **continuously**, at the same frequency as the flow metering. (raw measurements data shall be made available upon request by Rainbow or the VVB), and
* as close to the metering point as possible and prior to mixing with another stream, and
* using in-line or on-line analyzer.
Typical analytical technologies are based on gas chromatography, non-dispersive infrared spectroscopy (NDIR), and ultraviolet-visible (UV-Vis) spectroscopy. Concentration measurement systems shall be
* chosen according to the expected and actual composition of the stream, covering the detection range required by local/national standards or operational requirements, and
* **on-site calibration at commissioning** shall be performed against traceable calibration gases
### **Determination of biogenic fraction of CO****2**
Project Developers shall determine $$F\_B$$ according to Article 39 of the[ EU ETS monitoring and reporting](#user-content-fn-5)[^5], using either
* a mass balance approach of material inputs by type for every monitoring period, or
* continuous C14 testing over a representative period of time, following ISO 13833 or ASTM D6866 standard test methods, or
* other standards and analytical methods, subject to approval by Rainbow and the VVB.
### **Handling missing data**
Where a valid hourly reading cannot be obtained because equipment is **out of control, out of range, or out of operation**, a substitute value shall be determined for each missing hour:
* **For missing concentration data:** the substitute value shall be calculated as the average concentration over the monitoring period **plus twice the standard deviation.**
* **For data other than concentration:** the substitute value shall be derived from a mass balance or energy balance model of the process, and validated against the remaining measured parameters for a period of the same length as the data gap.
If measurement equipment is down for more than **5 consecutive days**, the Project Developer shall notify Rainbow without delay and propose corrective measures. Where the Project Developer is not the operator of the transport or storage infrastructure, a formal agreement shall be in place ensuring that all relevant measurement data and gap-filling records are communicated to the Project Developer in a timely manner.
[^1]: Depending on the type of stream (segregated or non-segregated) this can be the amount of CO2
* leaving the capture facility and entering the first transport segment
* entering a transport segment
* leaving a transport segment
* entering the storage site
* injected into geological storage
[^2]: Chinello, G.; Arellano, Y.; Span, R.; van Putten, D.; Abdulrahman, A.; Joonaki, E.; Arrhenius, K.; Murugan, A.; Toward standardized measurement of CO2 transfer in the CCS chain, Nexus, *1,* 100013, **2024**. [DOI](https://www.sciencedirect.com/science/article/pii/S2950160124000111#sec3)\
\
Mills, C.; Flow Measurement in support of Carbon Capture, Utilisation and Storage (CCUS), 2021. [DOI](https://www.researchgate.net/profile/Chris-Mills-6/publication/368881913_Flow_Measurement_in_support_of_Carbon_Capture_utilisation_and_Storage_CCUS/links/63ff432d0cf1030a5660c413/Flow-Measurement-in-support-of-Carbon-Capture-utilisation-and-Storage-CCUS.pdf)
[^3]: Common densitometer are nucleonic meter (using gamma-rays) meter or torsional resonators. Coriolis meter can also measure density of the stream.
[^4]: McKay, C; Nazeri, M.; Haghighi, H.; Erickson, D.; Recommendations for the selection of equation of state during design and operation of impure CO2 transport and storage, Proceedings of the 16th Greenhouse Gas Control Technologies Conference, **2022**. [DOI](https://doi.org/10.1016/j.ijggc.2023.103877)\
\
\
Vitali, M.; Leporini, M.; Masi, O.; Speranza, A.; Corvaro, F.; Marchetti, B.; Net zero Flow Assurance - Validation of various equations of state for the prediction of VLE and density of CO2-rich mixtures for CCUS applications, International Journal of Greenhouse Gas Control, *125,* 103877, **2023.** [DOI](https://doi.org/10.1016/j.ijggc.2023.103877)
[^5]: Commission Implementing Regulation (EU) 2018/2066 of 19 December 2018 on the monitoring and reporting of greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council and amending Commission Regulation (EU) No 601/2012. [URL](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A02018R2066-20240701).
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