Understanding biomass information shown on Retirement Statements

How biomass inputs into the green gas production process are classified and described on Retirement Statements

Producers may use a range of different biomass inputs (also referred to as feedstocks) to generate their biomethane. Those individual inputs can be given a classification as a product/co-product, residue, or waste.

The GGCS records information on feedstocks and classifications on our Registration Database which are displayed on the Retirement Statements provided to consumers.

The way this information is recorded and displayed has been updated as of July 29th 2020 and the table below shows which type of information you will see, depending on if a Retirement Statement has been downloaded before or after this date.


Information Shown pre-July 2020 under “Feedstock/technology”

Equivalent information shown post-July 2020 under “Biomass information”

MP or AC

Biomethane from products/co-products

GGCS - Biomass (Unspecified) Classification (Product/Co-product)

MR or AB

Biomethane from residues

GGCS - Biomass (Unspecified) Classification (Residue)

MW or AA

Biomethane from wastes

GGCS - Biomass (Unspecified) Classification (Waste)


Biogas from agricultural activities

GGCS - Biomass (Unspecified) Classification (Product/Co-product)


Biogas from food waste

GGCS - Biomass (Food Waste) Classification (Waste)


Biogas from domestic wastewater treatment

GGCS - Biomass (Sewage Sludge) Classification (Waste)


Biogas from a combination of these feedstocks

GGCS - Biomass (Unspecified) Classification (Unspecified)

As shown in the table, statements downloaded after the update have the potential to show an individual feedstock in the “Biomass” section and if that feedstock is considered a product, residue, or waste in the “Classification” section.  

The default information recorded in the Biomass section is “Unspecified”. While UK biomethane producers must accurately record every feedstock they use and the GGCS is shown this information, at this stage, we do not believe it is feasible or necessary to record this level of detail within our RGGOs. For example, a producer may use multiple types of energy crop as feedstocks and we will describe that as “Unspecified”.

The alternative, of issuing sperate RGGOs for maize, rye, grass, etc, would not be of value to a consumer while adding significant complexity to the issuing and transfer for RGGOs. However, we will consider on a case by case basis instances where stating feedstocks in the “Biomass” field may be of value.

We believe that the most valuable information for traders and consumers is the “Classification” section, which shows if the feedstocks were products, residues, or wastes. Issuing RGGOs according to classification leads to a maximum of three batches of RGGOs per plant per quarter, reducing the complexity for the Scheme and providing the market with batches that can be efficiently transferred and retired.

A note on historical changes to the process

RGGOs issued between December 2012 and September 2017 had an identifier of BA, BF, BS, or BC, and the biomass information recorded was determined by the predominant feedstock that the producer was using (without any feedstock-to-biomethane apportionment calculation).

If you are viewing a Retirement Statement showing these RGGOs and it has been downloaded before July 29th 2020, then you will see the information in the “technology/feedstock” field as detailed in the table in the second column. If you download that same statement after July 20th 2020, then this information will have been translated into the “biomass information” field as shown in the table. To ensure an accurate translation of the domestic wastewater and food waste codes the “biomass” function has been used.  

RGGOs issued from September 2017 onwards have had a technology/feedstock identifier of MP, MR, MW, AA, AB, or AC which was determined by conducting a feedstock-to-biomethane apportionment calculation.

If you are viewing a Retirement Statement download before July 29th 2020, then you will see the information in the “technology/feedstock” field as detailed in the table above in the second column. If you download that same statement after July 20th 2020, then this information will have been shown in the “biomass information” field as described in the table above in the third column.

Conducting a feedstock-to-biomethane apportionment calculation

Where a biomethane producer is using a feedstock or feedstocks that fall into a single classification, all of the RGGOs can be issued as a single batch with the same information recorded within them.   

Where a biomethane producer is using feedstocks that are from more than one classification, then they will provide evidence to the GGCS of their feedstock-to-biomethane apportionment and separate batches of RGGOs will be issued for amounts of biomethane produced from each group of feedstocks.

For example, the producer calculates that feedstocks which are classified as products were responsible for 60% of their biomethane production and that feedstocks classified as wastes were responsible for 40% of their biomethane production. Of the total kWh of biomethane injected in that quarter, RGGOs accounting for 60% of that total would be labelled as Biomass (Unspecified) Classification (Product/co-product). RGGOs accounting for 40% of that total would be labelled “Biomass (Unspecified) Classification (Waste).

Biogas, and therefore biomethane, yields vary between feedstocks and producers make feedstock-to-biomethane apportionment calculations based on the best available information. Producer’s calculation methodologies are assessed during an annual audit and this audit may be available from the producer on request. More information can be found in the Non-domestic RHI Sustainability Self-Reporting Guidance (version 2).

More information on the classification of the feedstocks used by each GGCS producer can be found here.

What counts as a Product, Residue, or Waste?

As part of their RHI claims UK biomethane producers agree with Ofgem via a Fuel and Measurement Sampling Questionnaire which classification each of their feedstocks falls into.
These classifications are:

Products – where the primary reason for a feedstocks production was for use as a fuel in the anaerobic digestion process it will be classified as a product. Examples include Maize, Rye, Wheat, and Sugar Beet crops. These are commonly referred to as “energy crops”.

Co-products – when a feedstock considered a product is produced there may be other useful products created as part of that process, which are then classified as co-products.

Residues – when a feedstock is“not the end product that a production process directly seeks to produce, [is] not a primary aim of the production process and the process has not been deliberately modified to produce it” (more details here), then it may be considered a residue. Examples include cereal straw, unsalable vegetables, vegetable peelings, and whey permeate.

Wastes – feedstocks that are substances or objects that would otherwise be discarded, or the holder would be required to discard, are considered wastes. Examples include food waste from domestic properties, food waste from commercial catering operations, sewage sludge, and animal slurry/manures.

Further information on the process of classifying feedstocks can be found in Section 4. Fuel Classification of the Non-domestic RHI Sustainability Self-Reporting Guidance (version 2).

If a Retirement Statement shows that the sustainability criteria met were the RHI’s, then that indicates that the above classification system was used. The biomass information will also show the prefix “GGCS”.

Biomethane producers may also determine the classification of their feedstocks according to other recognised Schemes. If this option is taken, then we will update this page to provide further details.

GGCS also issue RGGOs for bio-propane. Any technology/feedstock identifier beginning with C, for example, CA, CB, or CD, results in the biomass information showing as “BioLPG from Hydrogenated Vegetable Oils”

BioLPG is being distributed by Calor. For further information please visit their website.

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