Circularity Assessment

Projects that reduce GHG emissions and are issued Riverse Carbon Credits typically also contribute to a circular economy. The assessment of a project's circularity is considered under the co-benefits criteria and represents the Sustainable Development Goal (SDG) number 12.2.

The Material Circularity Indicator (MCI) is the selected measure of circularity, due to its comprehensive assessment of material flows and alignment with global standards, notably established by The Ellen MacArthur Foundation.

The MCI examines the mass of material flows throughout a product's lifecycle. It evaluates how efficiently materials circulate within a closed-loop system, assigning “more circular” scores to systems that minimize waste and optimize resource reuse. The formula uses input parameters such as material feedstock amount and type (e.g. from recycled, reused, or biological sources), recycling rates, and lifespan extension potential to quantify a product's circularity.

A detailed description and formulas for calculating the MCI are documented in the dedicated , on pages 22 to 31 (following the Product-level Methodology under the Whole product approach). Figure 3 summarizes the MCI material flows for biogas and natural gas production.

The MCI is a unitless indicator that varies from 0 to 1, where 0 represents a fully linear product and 1 is fully circular. The project scenario MCI is compared to the baseline scenario MCI, measuring how much more circular the project scenario is than the baseline.

The MCI methodology has been applied to biogas production using the input data presented in Table 9.

Figure 3 Summarized representation of the MCI material flows. *Energy recovery as part of a circular strategy only applies to biological materials following the MCI's conditions.

Table 9 All variables needed to calculate the Material Circularity Indicator (MCI) for the Riverse Biogas from anaerobic digestion methodology are detailed below. The full methodology and equations can be found in the dedicated .

Symbol	Definition by the MCI	Guidelines for the project scenario	Guidelines for the baseline scenario
M	Mass of a product	Total mass (kg) of gas produced, calculated based on the GWh of energy input into the gas grid in the project scenario according to: where, represents the mass of gas produced in one year, calculated based on the number of Functional Units produced (GWh) in the base year and the gas' LHV in kWh/m³. represents the amount of GWh injected into the grid, from the gas grid injection receipts. represents the gas calorific value, in kWh/m³. This is assumed to be 10, converted from Table 5. represents the biomethane density, in kg/m³, which is assumed 0.75 kg/m³. In the project scenario, the digestate produced shall also be considered in the final product weight as it has economic value. Thus, where, represents the product's final mass in the project scenario, calculated based on M and the amount of fertilizer thanks to the use of digestate. represents the amount of digestate produced. This is calculated according to the amount of feedstock input, according to Eq.2, in kg (without considering the transport emission factor).
Fr	Fraction of mass of a product's feedstock from recycled sources	Assumed zero
Fu	Fraction of mass of a product's feedstock from reused sources	Assumed zero
Fs	Fraction of a product's biological feedstock from Sustained production.	In the project scenario, feedstock is of biological origin except dedicated crops. According to Riverse's biogas methodology section 2.4, projects must adhere to specific limitations when using dedicated crops as feedstock. Consequently, dedicated crops are deemed "virgin" to not benefit from biological feedstock circularity.	The market gas mix is composed of natural gas, biomethane, and biogas. It is assumed that biological feedstock is used in biogas and biomethane, but not in natural gas production. Thus, Fs in the baseline scenario is the sum of the fraction of biogas and biomethane in the grid.
V	Material that is not from reuse, recycling or biological material from sustained production.	The amount of virgin materials used in the project scenario is the equivalent of dedicated crops used.	All the input materials, except the fraction related to biogas/biomethane described above, are considered virgin as no reuse, recycled, or biological materials are assumed in a status quo scenario.
Cr	Fraction of mass of a product being collected to go into a recycling process	Assumed zero because after the gas and digestate use, no product is left for recycling.
Cu	Fraction of mass of a product going into component reuse	Assumed zero as, after the gas use, no product is left for reuse except digestate in the project scenario (which is considered in the composting process below).
Cc	Fraction of mass of a product being collected to go into a composting process	This fraction represents the amount of digestate relative to the total mass of the final product ().	Although the fraction of biogas and biomethane in the baseline scenario generate digestate, the amount would be very small, and does not have a significant impact on the MCI. Thus, it is excluded from the calculation.
Ce	Fraction of mass of a product being collected for energy recovery where the material satisfies the requirements for inclusion	This fraction represents the amount of biomethane relative to the total mass of the final products ().	Energy recovery as part of a circular strategy only applies to biological materials, according to the MCI methodology. This value is assumed to be zero for natural gas. Thus, the final value considered is the sum of the fraction of biogas and biomethane in the grid.
Wo	Mass of unrecoverable waste through a product's material going into landfill, waste to energy and any other type of process where the materials are no longer recoverable	Following the MCI calculation methodology, this value is zero as all final product mass can be recovered.	Following the MCI calculation methodology, this value is equal to the mass of the final product (M) minus the fraction of biogas and biomethane in the grid.
Ec	Efficiency of the recycling process used for the portion of a product collected for recycling	Not considered as no recycled material is used.
Wc	Mass of unrecoverable waste generated in the process of recycling parts of a product	Not considered as no recycled material is used.
Ef	Efficiency of the recycling process used to produce recycled feedstock for a product	Not considered as no recycled material is used.
Wf	Mass of unrecoverable waste generated when producing recycled feedstock for a product	Not considered as no recycled material is used.
W	Mass of unrecoverable waste associated with a product	Following the MCI calculation methodology, this value is zero as all the final product mass can be recovered.	Following the MCI calculation methodology, this value is equal to the mass of the final product (M) minus the fraction of biogas/biomethane.
LFI	Linear flow index (LFI)	Varies from 0 to 1, where 1 is a completely linear flow and 0 is a completely restorative flow. In a circular project, the LFI shall be closer to zero, while the baseline shall be closer to 1.
L	Actual average lifetime of a product	Biomethane shall have similar properties to natural gas to be injected into the gas grid. It is assumed that the actual average lifetime of the product in both scenarios is equivalent, and therefore doesn’t affect the comparative calculations. It is assumed to be 1.
Lav	Average lifetime of an industry-average product of the same type
U	Actual average number of achieved during the use phase of a product	Biomethane shall have similar properties to natural gas to be injected into the gas grid. It is assumed that the actuarial average number of functional units of the product in both scenarios is equivalent, and therefore doesn’t affect the comparative calculations. It is assumed to be 1.
Uav	Average number of functional units achieved during the use phase of an industry-average product of the same type
X	Utility of a product (function of the product's lifespan and intensity of use)	Following the MCI methodology calculation, this is equal to 1.
MCIp	Material Circularity Indicator of a product	Varies from 0 to 1, where 0 represents a fully linear product and 1 is fully circular.