Proposed limit values for contaminants in biomethane based on health assessment criteria

This document explains an approach for assessment of limit values for contaminants that may be found
in biomethane. Limit values are generally required as an adjunct to a biomethane specification (such as
parts 1 and 2 of EN 16723, or an equivalent National specification) or as part of a Network Entry
Agreement for injection of biomethane into gas networks.
The methodology employed will permit derivation of limit values based solely on consideration of
potential for impact on human health and does not consider other impacts, such as integrity and
operation of plant and pipelines used to convey biomethane or appliances involved in its combustion or
other regulations like CLP regulation. Where consideration of such impacts would result in proposing
lower limit values than those based on health impacts, then the lowest limit values should generally be
proposed.

Vorgeschlagene Grenzwerte für Verunreinigungen in Biomethan auf Grundlage von Gesundheitsgefährdungskriterien

Valeurs limites proposées pour les contaminants dans le biométhane sur la base de critères d'évaluation de la santé

Le présent Rapport technique décrit une approche pour l'évaluation de valeurs limites pour les contaminants que l'on peut trouver dans le biométhane. Des valeurs limites sont généralement requises en complément d'une spécification de biométhane (comme les Parties 1 et 2 de l'EN 16723 ou spécification nationale équivalente) ou dans le cadre d'un accord d'entrée de réseau pour l'injection de biométhane dans les réseaux de gaz.
La méthodologie employée permettra d'établir des valeurs limites uniquement sur la base de l'examen de l'incidence potentielle sur la santé humaine, sans tenir compte des répercussions possibles sur les autres éléments, tels que l'intégrité et le fonctionnement des installations et canalisations servant à transporter le biométhane ou des appareils impliqués dans sa combustion, ni des autres règlements comme le règlement CLP. Si l'examen de ces répercussions conduit à proposer des valeurs limites inférieures à celles fondées sur l'incidence sur la santé, il convient en règle générale de proposer les valeurs limites les plus basses.

Predlagane mejne vrednosti za onesnaževala v biometanu na podlagi meril zdravstvene presoje

Ta dokument pojasnjuje pristop k ocenjevanju mejnih vrednosti za onesnaževala, ki jih je mogoče odkriti v biometanu. Mejne vrednosti so običajno zahtevane kot dodatek k specifikaciji biometana (npr. dela 1 in 2 standarda EN 16723 ali enakovredna nacionalna specifikacija) ali kot del pogodbe NEA (Network Entry Agreement) za vbrizgavanje biometana v plinska omrežja.
Uporabljena metodologija bo omogočala izpeljavo mejnih vrednosti izključno na podlagi upoštevanja morebitnega vpliva na človeško zdravje in ne upošteva drugih vplivov, kot sta celovitost ter delovanje obrata in cevovodov, ki se uporabljajo za prenos biometana, oziroma naprav, vključenih v njegovo zgorevanje, ali drugih uredb (npr. uredba CLP). Če bi upoštevanje takih vplivov pomenilo predlaganje nižjih mejnih vrednosti od tistih, ki temeljijo na vplivih na zdravje, je treba na splošno predlagati najnižje mejne vrednosti.

General Information

Status
Published
Public Enquiry End Date
01-Mar-2018
Publication Date
06-Nov-2018
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
29-Oct-2018
Due Date
03-Jan-2019
Completion Date
07-Nov-2018

Buy Standard

Technical report
kSIST-TP FprCEN/TR 17238:2018 - BARVE na PDF-str 11,18,27
English language
27 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day
Technical report
SIST-TP CEN/TR 17238:2018 - BARVE na PDF-str 11,17,18,25,27
English language
27 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17238:2018
01-februar-2018
Predlagane mejne vrednosti za onesnaževala v biometanu na podlagi kriterijev
zdravstvene presoje
Proposed limit values for contaminants in biomethane based on health assessment
criteria
Vorgeschlagene Grenzwerte für Verunreinigungen in Biomethan auf Grundlage von
Gesundheitsgefährdungskriterien

Valeurs limites proposées pour les contaminants dans le biométhane sur la base de

critères d'évaluation de la santé
Ta slovenski standard je istoveten z: FprCEN/TR 17238
ICS:
27.190 Biološki viri in drugi Biological sources and
alternativni viri energije alternative sources of energy
75.060 Zemeljski plin Natural gas
kSIST-TP FprCEN/TR 17238:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
kSIST-TP FprCEN/TR 17238:2018
---------------------- Page: 2 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 17238
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
December 2017
ICS
English Version
Proposed limit values for contaminants in biomethane
based on health assessment criteria

Valeurs limites proposées pour les contaminants dans Vorgeschlagene Grenzwerte für Verunreinigungen in

le biométhane sur la base de critères d'évaluation de la Biomethan auf Grundlage von

santé Gesundheitsgefährdungskriterien

This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC

408.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 17238:2017 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
Contents Page

European Foreword ...................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Symbols, units and abbreviated terms .................................................................................................... 8

4.1 Cg: maximum acceptable concentration in biomethane (mg/m ) ................................................ 8

4.2 Cexp: exposure concentration .................................................................................................................... 8

4.3 M: multiplier in the exposure model ........................................................................................................ 8

4.4 CAS number: Unique numerical identifier assigned by Chemical Abstracts Service .............. 8

5 Global Approach for assessment of limit values .................................................................................. 8

Figure 1 – Description of the methodology to apply to each contaminant ............................................... 9

5.1 Definition of the database for gas composition and HCVs ................................................................ 9

5.2 Definition of the exposure model ........................................................................................................... 10

5.3 Part III: Determination of COPCs ............................................................................................................ 10

6 Assessment and selection of Health Criteria Values: general guidance on assessment

and selection of HCVs .................................................................................................................................. 10

7 Application of the methodology: Biomethane injection into gas networks ............................ 11

Annex A (Informative) Example of different sources of HCVs .................................................................. 12

Table A.1 — examples of different sources of HCVs....................................................................................... 12

Annex B (Informative) Example of the application of the methodology ............................................... 13

B.1 General ............................................................................................................................................................. 13

Table B.1 — Contaminants present and their concentration in the example biogas ........................ 13

B.2 Conceptual Model ......................................................................................................................................... 13

Table B.2 — Conceptual model of exposure to contaminants in biomethane ...................................... 13

B.3 Chemicals of Potential Concern (COPCs) ............................................................................................. 14

The chemical analysis of the biogas shown in Table B.1 suggests that the contaminants

listed in Table B.3 should be considered to be COPCs, since they are present in
biogas and hence there is reliance on the upgrading and purification process to

remove them to an acceptable level. ..................................................................................................... 14

Table B.3 — List of contaminants considered to be COPCs ......................................................................... 14

B.4 Mathematical Exposure Model ................................................................................................................ 14

B.4.1 General ............................................................................................................................................................. 14

B.4.2 Modelling exposure concentrations – domestic cooking situation............................................ 15

Figure B.1 — Room concentration and exposure concentration predicted for ignition phase

release of contaminant (parameters as in Table 5, concentration of contaminant in

biomethane 1.0 mg/m ) ............................................................................................................................. 15

---------------------- Page: 4 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
Figure B.2 — Room concentration and exposure concentration predicted for
ignition/combustion and combustion-only phase release of contaminant

(parameters as in Table 5, concentration of contaminant in biomethane 1.0 mg/m ) ...... 16

Table B.4 — Exposure model parameters.......................................................................................................... 17

Table B.5 — Concentrations derived using the exposure model ............................................................... 17

Table 7 — values of the nine multipliers, Ma – Mc, M’a – M’c and M”a – M”c for each release

type .................................................................................................................................................................... 18

B.5 Selection of HCVs........................................................................................................................................... 18

Table B.7 — HCVs assigned to the COPCs released during the ignition phase and the

combustion phase ......................................................................................................................................... 18

B.6 Determination of the maximum tolerable concentration of each contaminant .................... 19

Table B.8 — Matrix illustrating the combinations of multiplier and HCV.............................................. 20

Table B.9 — Limit values arising from health criteria considerations ................................................... 20

Annex C (Informative) Details of the exposure model ................................................................................. 21

C.1 Introduction.................................................................................................................................................... 21

C.2 Nomenclature ................................................................................................................................................. 21

Table C.1 — Nomenclature ...................................................................................................................................... 21

C.3 Continuous releases ..................................................................................................................................... 22

C.4 Decay in concentration following cessation of release ................................................................... 22

Figure C.1 — Illustration of a continuous release and decay periods...................................................... 23

C.5 Average concentrations .............................................................................................................................. 23

Table C.1 — Equation for each pollutant type and each phase .................................................................. 24

Figure C.2 — Room concentration and exposure concentration predicted for ignition phase

release of contaminant (parameters as in Table 5, concentration of contaminant in

biomethane 1.0 mg/m ) ............................................................................................................................. 25

Figure C.3 — Room concentration and exposure concentration predicted for
ignition/combustion and combustion-only phase release of contaminant

(parameters as in Table 5, concentration of contaminant in biomethane 1.0 mg/m ) ...... 25

C.6 Use of multipliers .......................................................................................................................................... 26

C.7 Exposure model spreadsheet ................................................................................................................... 26

Bibliography ................................................................................................................................................................. 27

---------------------- Page: 5 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
European Foreword

This document (FprCEN/TR 17238:2017) has been prepared by Technical Committee CEN/TC 408

“Natural gas and biomethane for use in transport and biomethane for injection in the natural gas

network”, the secretariat of which is held by AFNOR.
This document is submitted to the Vote on TR.
---------------------- Page: 6 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
Introduction

This standard was prepared by CEN/TC 408 in response to the European Commission standardization

mandate M/475.

The Mandate asks for the development of a set of quality specifications for biomethane to be used as a

fuel for vehicle engines and to be injected in natural gas pipelines (network).

However, the scope of the standard was widened according to BT decision C109/2012 that redefined

the scope of CEN/TC 408: “Standardization of specifications for natural gas and biomethane as vehicle

fuel and of biomethane for injection in the natural gas grid, including any necessary related methods of

analysis and testing. Production process, source and the origin of the source are excluded”.

One of the aims of European policy in the field of energy is to increase the security of energy supply in

the EU as well as to contribute to reduce the emission of greenhouse gases accepted by the EU at Kyoto.

In this context a special focus is given to the development and use of energy from renewable sources.

Directive 2009/28/EC on the promotion of the use of energy from renewable sources and amending

and subsequently repealing Directives 2001/77/EC and 2003/30/EC stipulates clear aims regarding

the percentage of renewables in EU energy consumption and states the related need to support the

integration of energy from renewable sources into the energy networks including the establishment of

appropriate technical rules in line with Directive 2003/55/EC (Article 6) replaced by 2009/73/EC

(Article 8) for the realization of the competitive single European Gas Market and the technical

interoperability of gas networks, (network connection, gas quality, gas odorization and gas pressure

requirements).

Supporting the EU policy and therefore the maximization of the production and use of biomethane and

considering the absence of standards the European Commission DG ENER has included the injection of

biomethane in natural gas pipelines in Mandate M/475. Biomethane in this context can be produced

from biological (fermentation, digestion …) and thermochemical processes and shall be appropriate to

be used as a blending component to natural gas.
---------------------- Page: 7 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
1 Scope

This document explains an approach for assessment of limit values for contaminants that may be found

in biomethane. Limit values are generally required as an adjunct to a biomethane specification (such as

parts 1 and 2 of EN 16723, or an equivalent National specification) or as part of a Network Entry

Agreement for injection of biomethane into gas networks.

The methodology employed will permit derivation of limit values based solely on consideration of

potential for impact on human health and does not consider other impacts, such as integrity and

operation of plant and pipelines used to convey biomethane or appliances involved in its combustion or

other regulations like CLP regulation. Where consideration of such impacts would result in proposing

lower limit values than those based on health impacts, then the lowest limit values should generally be

proposed.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 16723-2:2017, Natural gas and biomethane for use in transport and biomethane for injection in the

natural gas network - Part 2: Automotive fuels specification
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
biogas

gas, comprising principally methane and carbon dioxide, obtained from the anaerobic digestion of

biomass
3.2
biomass

biological material from living, or recently living organisms, typically this may be plants or plant-

derived materials
3.3
biomethane

gas comprising principally methane, obtained from either upgrading of biogas or methanation of bio-

syngas
3.4
bio-syngas

gas, comprising principally carbon monoxide and hydrogen, obtained from gasification of biomass

3.5
contaminant

chemical with undesired properties which may be present in biomethane at a low concentration and for

which no maximum concentration is specified in EN 16723
---------------------- Page: 8 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
3.6
Chemicals Of Potential Concern
(COPC)

chemicals that may present a risk to the environment directly or after combustion

3.7
Health Criteria Value
(HCV)

generic term to describe a benchmark level of exposure to a chemical derived from available toxicity

data for the purposes of safeguarding human health. They are defined for instance by US EPA (US),

ANSES (FR), Environment Agency (UK), RIVM (NL), ARPA (IT). The unit is mg/m
3.8
limit value

maximum concentration of a contaminant that is allowed in a gas quality specification

3.9
natural gas

complex gaseous mixture of hydrocarbons, primarily methane, but generally includes ethane, propane

and higher hydrocarbons, and some non-combustible gases such as nitrogen and carbon dioxide

Note 1 to entry: Natural gas can also contain components or contaminants such as sulphur compounds and/or

other chemical species.
3.10
natural gas network
transmission network or local distribution system
3.11
non-threshold effect chemical
chemical that may theoretically pose a risk at any level of exposure
3.12
(Health) Risk

possibility that a harmful event (death, injury or loss) arising from exposure to a chemical or physical

agent may occur under specific conditions
3.13
threshold effect chemical

chemical which might be present in such concentrations that it might initiate a health risk of concern

3.14
upgrading of biogas
removal of carbon dioxide and contaminants from biogas
---------------------- Page: 9 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
4 Symbols, units and abbreviated terms
4.1 Cg: maximum acceptable concentration in biomethane (mg/m )
4.2 Cexp: exposure concentration
4.3 M: multiplier in the exposure model

4.4 CAS number: Unique numerical identifier assigned by Chemical Abstracts Service

5 Global Approach for assessment of limit values

The approach described in this technical report is similar to that commonly employed in environmental

health risk assessment, an example of which can be seen at the US Dept. of Energy’s Risk Assessment

Information System (RAIS) website [9]Error! Reference source not found..

Conventional health risk assessments aims to assess and quantify the health risk presented by a

particular activity. If the risk exceeds a maximum acceptable value, then mitigation actions are assessed

and implemented. In conventional risk assessment, therefore, the output is a (quantified) level of risk

associated with the process. However, in the context of specifying limit values for contaminants in

biomethane the INVERSE of this risk assessment procedure is followed: an acceptable level of risk is

agreed and the activity (in this instance injection of biomethane into natural gas grids) is modified by

implementing an appropriate gas quality specification. In this situation, the acceptable level of risk is an

input to the risk assessment procedure and the output is a gas quality specification. Such a specification

will contain limit values for content of those contaminants that are likely to be present.

Note The contaminants that are likely to be present that can present a risk to the environment are

commonly called “Chemicals of Potential Concern” (COPCs).

Similar approaches have been previously employed for development of gas quality specifications for

biomethane: in 2008 in France (Afsset [1]) and in 2012 in the UK (UK Environment Agency [7]). This

approach may be used whenever compounds of interest are added in the list of data. In addition, several

realistic scenarios should be assessed in order to identify the worst case that will lead to the most

appropriate limit value.
These scenarios depend at least on these elements:
• The national laws and regulations,
• The conceptual model designed,
• The national practices,
• Specific assumptions.

The procedure for assessing limit values in this Technical Report can be summarized in following

scheme (Figure 1):
---------------------- Page: 10 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
Figure 1 – Description of the methodology to apply to each contaminant
5.1 Definition of the database for gas composition and HCVs

When assessing limit values for contaminants present in biomethane, the point at which COPCs are

identified will depend on the context, i.e. whether a site-specific or generic assessment is being carried

out and whether a detailed chemical analysis of biogas/biomethane is available or not.

Trace compounds will strongly be influenced by its production process. Production processes for

biomethane vary significantly. For example:

• Anaerobic digestion of a wide range of biomass feedstocks, followed by upgrading (carbon dioxide

removal) and purification (removal of contaminants).

• Gasification of a wide range of biomass feedstocks to a bio-syngas, followed by purification and

upgrading (water gas shift and methanation).

It means that the database of the target compounds is defined using gas analysis and literature. Each

target compound should be described with its CAS number. C (concentration to be expected in

exp
biomethane) will be estimated also and included in the database.

Health Criteria Values (HCVs) are obtained for each contaminant, based on expert assessment

reported in the literature and the scenario considered. At the end of the process, one HCV will be

---------------------- Page: 11 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)

obtained for each compound and each scenario. This methodology should be applied when HCV for the

target compound is available. Assessment and choice of HCVs are discussed in Section Error! Reference

source not found..
5.2 Definition of the exposure model
The exposure model is usually dependant on national practices.

For each scenario, A “Source-Pathway-Receptor” conceptual model of exposure is agreed. The

conceptual model clarifies the assumptions about the Source (i.e. how a particular contaminant arises),

the Receptor (i.e. the environment/entity that is exposed to the contaminant and for which impact is

assessed) and the Pathway (i.e. how the contaminant is transported from the Source to the Receptor).

Based on the stated assumptions and boundaries of the conceptual model, a mathematical

exposure model is derived. The exposure model permits assessment of the ratio of concentration of a

given contaminant in the Source to the average concentration to which the Receptor is likely to be

exposed. This ratio is designated the “multiplier” (symbol M) and defined as in Formula (1).

Formula 1: multiplier
[1]

Because the exposure model is based on the conceptual model and its assumptions, then it too will

usually be specific to a particular country or national situation.

For each scenario, a specific Cg is established from its exposure model and selected HCV. The maximum

acceptable concentration is taken to be the lowest Cg value of these scenarios.
5.3 Part III: Determination of COPCs

The maximum acceptable concentration of each contaminant at the Source is assessed from the product

of the HCV and the Multiplier (Formula (2):
Formula 2: Maximum acceptable concentration at the source
[2]
Cg is usually expressed in mg/m .

When assessing combustion product of a contaminant, then the HCV of the combustion product and not

the contaminant itself is employed. In this situation, the relationship between the quantity of the

combustion product and the quantity of the contaminant in biomethane is required.

Cg is compared to Cexp to estimate if this chemical should be targeted as a COPC.

In the approach used in the “Risk Assessment Information System” (RAIS) of the US Department of

Energy , identification of COPCs is carried out at an early stage so as to limit the number of chemicals

for which risk assessment is carried out. Generally speaking, it is impractical to specify limit values for

large numbers of contaminants and so some form of reduction in the number of COPCs to be covered is

required if limit values are to be specified in a gas quality specification.
6 Assessment and selection of Health Criteria Values: general guidance on
assessment and selection of HCVs

Detailed guidance on assessment and selection of HCVs is available in a number of sources ((8)(6)) and

so only general advice is provided in this Technical Report. The basic toxicological approaches to

US Department of Energy. (2016, March). Risk Assessment Information System. https://rais.ornl.gov/

---------------------- Page: 12 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)

deriving HCVs for environmental chemicals are similar throughout the international scientific

community. However, with so many different organisations conducting risk assessments and regulatory

bodies each working to the unique wording of their national legislation, inevitable differences exist in

the precise methods followed and terminology used.

Whilst the approach employed in this Technical Report is consistent with that generally applied in most

countries, it is generally the case that no single set of common HCVs will be available and so values will

often need to be obtained from a variety of sources (Cf. Annex A).

Generally HCVs are set by National or International expert panels and although there may often

be international agreement, for some chemicals conflicting values may exist. In such situations

users of this protocol are recommended to seek advice from appropriate National expert bodies, taking

into account the National regulatory situation covering biomethane injection into gas grids. HCVs could

also be subject to guidance or regulation from National Expert bodies.
7 Application of the methodology: Biomethane injection into gas networks

Annex B illustrates the application of the methodology outlined in this Technical Report by way of an

example that deals with injection of biomethane into a gas distribution network. The conceptual model

considers the pathway from Source to Receptor to be inhalation of biomethane and its combustion

products released during cooking operations in a domestic property. Because these are well understood

operations it can be modelled using a deterministic mathematical model, where the outcome (i.e.

quantification of exposure to contaminants) will always be the same for the same inputs.

This example is an illustration of the methodology and should not be taken to be representative of a

particular national situation.

An alternative conceptual model could consider inhalation of biomethane that is released as a result of

undetected leaks from pipework within a domestic property. However, estimating exposure to

contaminants would require a stochastic mathematical model because there are a number of processes

involved in the pathway that contain an element of randomness. For example:

• The minimum concentration of biomethane in a room that is detectable by the occupant. Although

all distributed gas is odorised, the lowest concentration at which biomethane is detectable will vary

from person to person.

• Not all residencies have leaking pipework and the distribution of numbers of leaks of a given size

will vary for all residencies.

• Occupancy varies, both in terms of fraction of the day that a residence is occupied and the number

and ages of occupants.

In principle a stochastic exposure model could be developed using probability density functions that

described each of the above processes and which would provide estimates of multipliers at a chosen

probability level. However, an example of such an approach is not provided in this Technical Report.

---------------------- Page: 13 ----------------------
kSIST-TP FprCEN/TR 17238:2018
FprCEN/TR 17238:2017 (E)
Annex A
(Informative)
Example of different sources of HCVs

These examples given in Table A.1 are extracted from a French study by INERIS. For a set of several

compounds, sources to define HCV come from several countries or National experts’ panel. They are

defined under specific conditions which are further explained in the references.
Table A.1 — examples of different sources of HCVs
HCV - Inhalation pathway -
CAS Substances
Threshold toxicity
(mg/m3) Références
75–01–4 Vinyl chloride 56 RIVM, 2001
156–59–2 cis-1,2-Dichloroethene 6 RIVM, 2007
71–55–6 1,1,1-trichloroethane (1,1,1-TCA) 1 OEHHA, 2008
79–01–6 Trichloroethylene (TCE) 2 US-EPA, 2011
127–18–4 Tetrachloroethylene (PCE) 4 US-EPA, 2011
75–09–2 Dichloromethane 4 OEHHA, 2000
67–66–3 Trichloromethane (chloroforme) 63 AFSSET, 2008
...

SLOVENSKI STANDARD
SIST-TP CEN/TR 17238:2018
01-december-2018
Predlagane mejne vrednosti za onesnaževala v biometanu na podlagi meril
zdravstvene presoje
Proposed limit values for contaminants in biomethane based on health assessment
criteria
Vorgeschlagene Grenzwerte für Verunreinigungen in Biomethan auf Grundlage von
Gesundheitsgefährdungskriterien

Valeurs limites proposées pour les contaminants dans le biométhane sur la base de

critères d'évaluation de la santé
Ta slovenski standard je istoveten z: CEN/TR 17238:2018
ICS:
27.190 Biološki viri in drugi Biological sources and
alternativni viri energije alternative sources of energy
75.060 Zemeljski plin Natural gas
SIST-TP CEN/TR 17238:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST-TP CEN/TR 17238:2018
---------------------- Page: 2 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238
TECHNICAL REPORT
RAPPORT TECHNIQUE
April 2018
TECHNISCHER BERICHT
ICS 75.160.30; 27.190
English Version
Proposed limit values for contaminants in biomethane
based on health assessment criteria

Valeurs limites proposées pour les contaminants dans Vorgeschlagene Grenzwerte für Verunreinigungen in

le biométhane sur la base de critères d'évaluation de la Biomethan auf Grundlage von

santé Gesundheitsgefährdungskriterien

This Technical Report was approved by CEN on 9 April 2018. It has been drawn up by the Technical Committee CEN/TC 408.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17238:2018 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 6

2 Normative references .................................................................................................................................... 6

3 Terms and definitions ................................................................................................................................... 6

4 Symbols, units and abbreviated terms .................................................................................................... 8

4.1 Cg: maximum acceptable concentration in biomethane (mg/m ) ................................................ 8

4.2 Cexp: exposure concentration .................................................................................................................... 8

4.3 M: multiplier in the exposure model ........................................................................................................ 8

4.4 CAS number: Unique numerical identifier assigned by Chemical Abstracts Service .............. 8

5 Global Approach for assessment of limit values .................................................................................. 8

5.1 General ................................................................................................................................................................ 8

5.2 Definition of the database for gas composition and HCVs ................................................................ 9

5.3 Definition of the exposure model ........................................................................................................... 10

5.4 Part III: Determination of COPCs ............................................................................................................ 10

6 Assessment and selection of Health Criteria Values: general guidance on assessment

and selection of HCVs .................................................................................................................................. 10

7 Application of the methodology: Biomethane injection into gas networks ............................ 11

Annex A (Informative) Example of different sources of HCVs .................................................................. 12

Annex B (Informative) Example of the application of the methodology ............................................... 13

B.1 General ............................................................................................................................................................. 13

B.2 Conceptual Model ......................................................................................................................................... 13

B.3 Chemicals of Potential Concern (COPCs) ............................................................................................. 14

B.4 Mathematical Exposure Model ................................................................................................................ 14

B.4.1 General ............................................................................................................................................................. 14

B.4.2 Modelling exposure concentrations – domestic cooking situation............................................ 15

B.5 Selection of HCVs .......................................................................................................................................... 18

B.6 Determination of the maximum tolerable concentration of each contaminant ................... 19

Annex C (Informative) Details of the exposure model ................................................................................. 21

C.1 Introduction ................................................................................................................................................... 21

C.2 Nomenclature ................................................................................................................................................ 21

C.3 Continuous releases .................................................................................................................................... 22

C.4 Decay in concentration following cessation of release .................................................................. 22

C.5 Average concentrations ............................................................................................................................. 23

C.6 Use of multipliers ......................................................................................................................................... 26

---------------------- Page: 4 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)

C.7 Exposure model spreadsheet ................................................................................................................... 26

Bibliography ................................................................................................................................................................. 27

---------------------- Page: 5 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
European foreword

This document (CEN/TR 17238:2018) has been prepared by Technical Committee CEN/TC 408

“Natural gas and biomethane for use in transport and biomethane for injection in the natural gas grid”,

the secretariat of which is held by AFNOR.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association.
---------------------- Page: 6 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Introduction

This standard was prepared by CEN/TC 408 in response to the European Commission standardization

mandate M/475.

The Mandate asks for the development of a set of quality specifications for biomethane to be used as a

fuel for vehicle engines and to be injected in natural gas pipelines (network).

However, the scope of the standard was widened according to BT decision C109/2012 that redefined

the scope of CEN/TC 408: “Standardization of specifications for natural gas and biomethane as vehicle

fuel and of biomethane for injection in the natural gas grid, including any necessary related methods of

analysis and testing. Production process, source and the origin of the source are excluded”.

One of the aims of European policy in the field of energy is to increase the security of energy supply in

the EU as well as to contribute to reduce the emission of greenhouse gases accepted by the EU at Kyoto.

In this context a special focus is given to the development and use of energy from renewable sources.

Directive 2009/28/EC on the promotion of the use of energy from renewable sources and amending

and subsequently repealing Directives 2001/77/EC and 2003/30/EC stipulates clear aims regarding

the percentage of renewables in EU energy consumption and states the related need to support the

integration of energy from renewable sources into the energy networks including the establishment of

appropriate technical rules in line with Directive 2003/55/EC (Article 6) replaced by 2009/73/EC

(Article 8) for the realization of the competitive single European Gas Market and the technical

interoperability of gas networks, (network connection, gas quality, gas odorization and gas pressure

requirements).

Supporting the EU policy and therefore the maximization of the production and use of biomethane and

considering the absence of standards the European Commission DG ENER has included the injection of

biomethane in natural gas pipelines in Mandate M/475. Biomethane in this context can be produced

from biological (fermentation, digestion …) and thermochemical processes and it is essential that it is

appropriate to be used as a blending component to natural gas.
---------------------- Page: 7 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
1 Scope

This document explains an approach for assessment of limit values for contaminants that may be found

in biomethane. Limit values are generally required as an adjunct to a biomethane specification (such as

parts 1 and 2 of EN 16723, or an equivalent National specification) or as part of a Network Entry

Agreement for injection of biomethane into gas networks.

The methodology employed will permit derivation of limit values based solely on consideration of

potential for impact on human health and does not consider other impacts, such as integrity and

operation of plant and pipelines used to convey biomethane or appliances involved in its combustion or

other regulations like CLP regulation. Where consideration of such impacts would result in proposing

lower limit values than those based on health impacts, then the lowest limit values should generally be

proposed.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 16723-1:2016, Natural gas and biomethane for use in transport and biomethane for injection in the

natural gas network — Part 1: Specifications for biomethane for injection in the natural gas network

EN 16723-2:2017, Natural gas and biomethane for use in transport and biomethane for injection in the

natural gas network — Part 2: Automotive fuels specification
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
biogas

gas, comprising principally methane and carbon dioxide, obtained from the anaerobic digestion of

biomass
3.2
biomass

biological material from living, or recently living organisms, typically this may be plants or plant-

derived materials
3.3
biomethane

gas comprising principally methane, obtained from either upgrading of biogas or methanation of bio-

syngas
3.4
bio-syngas

gas, comprising principally carbon monoxide and hydrogen, obtained from gasification of biomass

---------------------- Page: 8 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
3.5
contaminant

chemical with undesired properties which may be present in biomethane at a low concentration and for

which no maximum concentration is specified in EN 16723
3.6
Chemicals Of Potential Concern
(COPC)

chemicals that may present a risk to the environment directly or after combustion

3.7
Health Criteria Value
(HCV)

generic term to describe a benchmark level of exposure to a chemical derived from available toxicity

data for the purposes of safeguarding human health. They are defined for instance by US EPA (US),

ANSES (FR), Environment Agency (UK), RIVM (NL), ARPA (IT). The unit is mg/m
3.8
limit value

maximum concentration of a contaminant that is allowed in a gas quality specification

3.9
natural gas

complex gaseous mixture of hydrocarbons, primarily methane, but generally includes ethane, propane

and higher hydrocarbons, and some non-combustible gases such as nitrogen and carbon dioxide

Note 1 to entry: Natural gas can also contain components or contaminants such as sulphur compounds and/or

other chemical species.
3.10
natural gas network
transmission network or local distribution system
3.11
non-threshold effect chemical
chemical that may theoretically pose a risk at any level of exposure
3.12
(Health) Risk

possibility that a harmful event (death, injury or loss) arising from exposure to a chemical or physical

agent may occur under specific conditions
3.13
threshold effect chemical

chemical which might be present in such concentrations that it might initiate a health risk of concern

3.14
upgrading of biogas
removal of carbon dioxide and contaminants from biogas
---------------------- Page: 9 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
4 Symbols, units and abbreviated terms
4.1 Cg: maximum acceptable concentration in biomethane (mg/m )
4.2 Cexp: exposure concentration
4.3 M: multiplier in the exposure model

4.4 CAS number: Unique numerical identifier assigned by Chemical Abstracts Service

5 Global Approach for assessment of limit values
5.1 General

The approach described in this technical report is similar to that commonly employed in environmental

health risk assessment, an example of which can be seen at the US Dept. of Energy’s Risk Assessment

Information System (RAIS) website [9].

Conventional health risk assessments aims to assess and quantify the health risk presented by a

particular activity. If the risk exceeds a maximum acceptable value, then mitigation actions are assessed

and implemented. In conventional risk assessment, therefore, the output is a (quantified) level of risk

associated with the process. However, in the context of specifying limit values for contaminants in

biomethane the INVERSE of this risk assessment procedure is followed: an acceptable level of risk is

agreed and the activity (in this instance injection of biomethane into natural gas grids) is modified by

implementing an appropriate gas quality specification. In this situation, the acceptable level of risk is an

input to the risk assessment procedure and the output is a gas quality specification. Such a specification

will contain limit values for content of those contaminants that are likely to be present.

NOTE The contaminants that are likely to be present that can present a risk to the environment are

commonly called “Chemicals of Potential Concern” (COPCs).

Similar approaches have been previously employed for development of gas quality specifications for

biomethane: in 2008 in France (Afsset [1]) and in 2012 in the UK (UK Environment Agency [7]). This

approach may be used whenever compounds of interest are added in the list of data. In addition, several

realistic scenarios should be assessed in order to identify the worst case that will lead to the most

appropriate limit value.
These scenarios depend at least on these elements:
• The national laws and regulations,
• The conceptual model designed,
• The national practices,
• Specific assumptions.

The procedure for assessing limit values in this Technical Report can be summarized in following

scheme (Figure 1):
---------------------- Page: 10 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Figure 1 — Description of the methodology to apply to each contaminant
5.2 Definition of the database for gas composition and HCVs

When assessing limit values for contaminants present in biomethane, the point at which COPCs are

identified will depend on the context, i.e. whether a site-specific or generic assessment is being carried

out and whether a detailed chemical analysis of biogas/biomethane is available or not.

Trace compounds will strongly be influenced by its production process. Production processes for

biomethane vary significantly. For example:

• Anaerobic digestion of a wide range of biomass feedstocks, followed by upgrading (carbon dioxide

removal) and purification (removal of contaminants).

• Gasification of a wide range of biomass feedstocks to a bio-syngas, followed by purification and

upgrading (water gas shift and methanation).

It means that the database of the target compounds is defined using gas analysis and literature. Each

target compound should be described with its CAS number. C (concentration to be expected in

exp
biomethane) will be estimated also and included in the database.

Health Criteria Values (HCVs) are obtained for each contaminant, based on expert assessment

reported in the literature and the scenario considered. At the end of the process, one HCV will be

---------------------- Page: 11 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)

obtained for each compound and each scenario. This methodology should be applied when HCV for the

target compound is available. Assessment and choice of HCVs are discussed in Clause 6.

5.3 Definition of the exposure model
The exposure model is usually dependant on national practices.

For each scenario, A “Source-Pathway-Receptor” conceptual model of exposure is agreed. The

conceptual model clarifies the assumptions about the Source (i.e. how a particular contaminant arises),

the Receptor (i.e. the environment/entity that is exposed to the contaminant and for which impact is

assessed) and the Pathway (i.e. how the contaminant is transported from the Source to the Receptor).

Based on the stated assumptions and boundaries of the conceptual model, a mathematical

exposure model is derived. The exposure model permits assessment of the ratio of concentration of a

given contaminant in the Source to the average concentration to which the Receptor is likely to be

exposed. This ratio is designated the “multiplier” (symbol M) and defined as in Formula (1).

Formula 1: multiplier
[1]

Because the exposure model is based on the conceptual model and its assumptions, then it too will

usually be specific to a particular country or national situation.

For each scenario, a specific Cg is established from its exposure model and selected HCV. The maximum

acceptable concentration is taken to be the lowest Cg value of these scenarios.
5.4 Part III: Determination of COPCs

The maximum acceptable concentration of each contaminant at the Source is assessed from the product

of the HCV and the Multiplier (Formula (2):
Formula 2: Maximum acceptable concentration at the source
[2]
Cg is usually expressed in mg/m .

When assessing combustion product of a contaminant, then the HCV of the combustion product and not

the contaminant itself is employed. In this situation, the relationship between the quantity of the

combustion product and the quantity of the contaminant in biomethane is required.

Cg is compared to Cexp to estimate if this chemical should be targeted as a COPC.

In the approach used in the “Risk Assessment Information System” (RAIS) of the US Department of

Energy , identification of COPCs is carried out at an early stage so as to limit the number of chemicals

for which risk assessment is carried out. Generally speaking, it is impractical to specify limit values for

large numbers of contaminants and so some form of reduction in the number of COPCs to be covered is

required if limit values are to be specified in a gas quality specification.
6 Assessment and selection of Health Criteria Values: general guidance on
assessment and selection of HCVs

Detailed guidance on assessment and selection of HCVs is available in a number of sources ((8)(6)) and

so only general advice is provided in this Technical Report. The basic toxicological approaches to

deriving HCVs for environmental chemicals are similar throughout the international scientific

US Department of Energy. (2016, March). Risk Assessment Information System. https://rais.ornl.gov/

---------------------- Page: 12 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)

community. However, with so many different organisations conducting risk assessments and regulatory

bodies each working to the unique wording of their national legislation, inevitable differences exist in

the precise methods followed and terminology used.

Whilst the approach employed in this Technical Report is consistent with that generally applied in most

countries, it is generally the case that no single set of common HCVs will be available and so values will

often need to be obtained from a variety of sources (see Annex A).

Generally HCVs are set by National or International expert panels and although there may often

be international agreement, for some chemicals conflicting values may exist. In such situations

users of this protocol are recommended to seek advice from appropriate National expert bodies, taking

into account the National regulatory situation covering biomethane injection into gas grids. HCVs could

also be subject to guidance or regulation from National Expert bodies.
7 Application of the methodology: Biomethane injection into gas networks

Annex B illustrates the application of the methodology outlined in this Technical Report by way of an

example that deals with injection of biomethane into a gas distribution network. The conceptual model

considers the pathway from Source to Receptor to be inhalation of biomethane and its combustion

products released during cooking operations in a domestic property. Because these are well understood

operations it can be modelled using a deterministic mathematical model, where the outcome (i.e.

quantification of exposure to contaminants) will always be the same for the same inputs.

This example is an illustration of the methodology and should not be taken to be representative of a

particular national situation.

An alternative conceptual model could consider inhalation of biomethane that is released as a result of

undetected leaks from pipework within a domestic property. However, estimating exposure to

contaminants would require a stochastic mathematical model because there are a number of processes

involved in the pathway that contain an element of randomness. For example:

• The minimum concentration of biomethane in a room that is detectable by the occupant. Although

all distributed gas is odorised, the lowest concentration at which biomethane is detectable will vary

from person to person.

• Not all residencies have leaking pipework and the distribution of numbers of leaks of a given size

will vary for all residencies.

• Occupancy varies, both in terms of fraction of the day that a residence is occupied and the number

and ages of occupants.

In principle a stochastic exposure model could be developed using probability density functions that

described each of the above processes and which would provide estimates of multipliers at a chosen

probability level. However, an example of such an approach is not provided in this Technical Report.

---------------------- Page: 13 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Annex A
(Informative)
Example of different sources of HCVs

These examples given in Table A.1 are extracted from a French study by INERIS. For a set of several

compounds, sources to define HCV come from several countries or National experts’ panel. They are

defined under specific conditions which are further explained in the references.
Table A.1 — examples of different sources of HCVs
HCV - Inhalation pathway -
CAS Substances
Threshold toxicity
(mg/m3) References
75–01–4 Vinyl chloride 56 RIVM, 2001
156–59–2 cis-1,2-Dichloroethene 6 RIVM, 2007
71–55–6 1,1,1-trichloroethane (1,1,1-TCA) 1 OEHHA, 2008
79–01–6 Trichloroethylene (TCE) 2 US-EPA, 2011
127–18–4 Tetrachloroethylene (PCE) 4 US-EPA, 2011
75–09–2 Dichloromethane 4 OEHHA, 2000
67–66–3 Trichloromethane (chloroforme) 63 AFSSET, 2008
(TCM)
56–23–5 Tetrachloromethane (TCC) 38 AFSSET, 2008
75–25–2 Tribromomethane No value
---------------------- Page: 14 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Annex B
(Informative)
Example of the application of the methodology
B.1 General

This example illustrates the procedure for setting limit values for contaminants in biomethane based on

health assessment criteria. The procedure follows the five-step approach described in clause 5.

Additional details of individual steps is provided in subsequent annex.

In general, different realistic situations in which human beings are exposed to unburned biomethane

and to flue gasses of biomethane are defined and the most severe one will be used to set the limit value.

In this example, biomethane is to be injected into a 2 barg pressure gas distribution network and is

combusted in a domestic cooking situation. The biomethane is produced by upgrading (removal of

carbon dioxide) and purification (removal of contaminants) of a biogas that is produced by anaerobic

digestion of sewage sludge. A chemical analysis of the biogas demonstrates that contaminants are

present at the following concentrations (Table B.1):
Table B.1 — Contaminants present and their concentration in the example biogas
Contaminant Units Concentration
Formaldehyde mg/m 0,05
D-limonene mg/m 2,53
Dichloromethane mg/m 1,5
Arsenic µg/m 5,4
B.2 Conceptual Model

The conceptual model is based on the injection of biomethane into a gas distribution network and

subsequent exposure to occupants of a domestic property to which gas is conveyed.

Table B.2 below sets out the main assumptions regarding a conceptual model of exposure to

contaminants contained in biomethane.
Table B.2 — Conceptual model of exposure to contaminants in biomethane
Assumption Notes

Source: Biomethane injected into a gas grid Although typical biomethane production

for conveyance to a consumer’s and injection facilities are relatively
premises. small. Injection is commonly into low
pressure systems where demand may be
low. The gas conveyed within the gas
pipeline is therefore considered to be
100 % biomethane.
Pathway: Two pathways are considered: A gas cooker hob is assumed to be the
most common unflued gas appliance.
a) Inhalation of unburnt biomethane
released from a gas cooker hob
---------------------- Page: 15 ----------------------
SIST-TP CEN/TR 17238:2018
CEN/TR 17238:2018 (E)
Assumption Notes
prior to its ignition.
b) Inhalation of contaminants or
products of combustion of
contaminants released whilst a
gas cooker hob is in use.
Receptor: Human acute and chronic exposure It is assumed in this example that
through inhalation during cooking cooking is carried out in a separate,
operations. typical domestic kitchen by adults. If
children and elderly people are expected
to be present in this kitchen, then an
additional factor can be applied.
B.3 Chemicals of Potential Concern (COPCs)

The chemical analysis of the biogas shown in Table B.1 suggests that the contaminants listed in

Table B.3 should be considered to be COPCs, since they are present in biogas and hence there is reliance

on the upgrading and purification process to remove them to an acceptable level.
Table B.3 — List of contaminants considered to be COPCs
Contaminant
Formaldehyde
D-limonene
Dichloromethane
Hydrogen Chloride
Arsen
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.