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Standards for biomethane as vehicle fuel and for injection into the natural gas grid

22 March 2013

Arthur Wellinger

European Biogas Association

Deliverable 3.6 WG2

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Table of contents

Standards for biomethane as fuel and for injection...................................1

1. Starting position.......................................................................................3

2. The mandate and working groups of CEN TC408 .......................4

3. Experts groups..........................................................................................5

4. Open points to be discussed .............................................................10

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Deliverable 3.6 2nd discussion paper as of March 2013-03-04

Development of standards

1. Starting position

By end of 2012 in eleven European countries biogas was upgraded to

biomethane. In nine countries thereof biomethane was injected into the

grid. The longest experience has Sweden and Switzerland which started

back in the early 90ies.

All of the biomethane countries developed standards for injection (plus

some more countries not injecting biomethane yet) however, a lot of

differences could be found in fundamental aspects such as parameters

and/or concentrations of compounds other than methane, with variations

even up to a factor of 100 (i.e. for mandated oxygen levels). In the past

years, there have been two EU funded projects aiming to develop common

standards for biomethane injection in the natural gas grid. During the FP6

project Biogasmax, a proposal was developed1 which wanted to find a

compromise between stringent formulated parameters created by the

national DSOs and parameters that could be achieved at reasonable prices

and process energy.

Another approach was made by Marcogaz, a technical association of the

natural gas industry. They came close to an excellent solution until the

different DSOs started to water down the proposal. The final proposal could

not find common ground and was abandoned.

During the discussion and formulation of the GGG project, an existing CEN

groups could take over a mandate from the European Commission directly

related to the topic, DG ENER’s Mandate M/475. The GGG work programme

(WP3/WG2) on biomethane parameters therefore planned a close

collaboration with CEN if ever they would start their work but also keep

contacts with IEA Bioenergy Task 37 and Biogasmax.

Arthur Wellinger, project partner on behalf of EBA and WP3 leader is

directly involved with IEA Bioenergy Task 37 work, acting in the agreement

as Technical Coordinator and has therefore easy access to their data. The

link to the (completed) Biogasmax project is also granted because Arthur

Wellinger was directly involved as responsible project partner of the Swiss

partner Berne. As such he was co-author of the recommendations for

injection parameters.

1 www.biogasmax.eu/

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Shortly after the start of the GGG project the EC decided to allocate the

above-mentioned mandate to a new CEN technical committee (CEN TC

408) to develop a standard for both, biomethane as a fuel and for injection,

and this was the reason why the GGG consortium decided to fully

collaborate with this group under formation. This was possible as two

project partners, EBA and NGVA Europe had the right to participate in the

TC as specialized European Associations.

Specific contribution of GGG to the CEN TC408 commission:

GreenGasGrids is represented in CEN TC408 through two of the consortium

partners, i.e. EBA and NGVA Europe. Both partners represent the voice of

the practice. EBA stands for the needs of biogas and upgrading plant

operators as well as of the plant providers. EBA is supported within the

CEN group by two representative of member associations acting within

their country representation: The German Biogas Association (Claudius da

Costa Gomez) and Club Biogaz (Christophe Mandereau). NGVA is the voice

of the engine manufacturers that are in part also directly involved in CEN

(Scania, Volkswagen).

2. The mandate and working groups of CEN TC408

After several discussions between CEN and the Commission, CEN was given

the mandate to develop, as a first step:

• A European Standard for a quality specification for biomethane to be

used as a fuel for vehicles;

• European deliverables such as Technical Specifications or European

Norms for quality specification of biomethane to be injected into

natural gas pipelines transporting either H-gas or L-gas.

The CEN technical experts should consider whether it is possible and

desirable for the proper functioning of the market to develop only one

European Standard addressing the requirements of both applications.

The European Standard on biomethane was to include no unnecessarily

restrictive requirements, as long as the proper functioning in the intended

applications could be guaranteed.

Because the biomethane quality for vehicle fuel is closely related to the

quality of natural gas – which has not been defined so far – the discussion

cannot be separated into two CEN TCs. The work of CEN/TC 408 was

therefore extended and addressed also the issue of CNG (Compressed

Natural Gas) as a fuel, and blends of fossil CNG with biomethane under the

TC umbrella.

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Therefore, the new scope of CEN/TC 408 encompasses now both

biomethane and natural gas as fuels and biomethane for injection into

natural gas grids.

The founding meeting of the CEN TC 408 took place on September 16,

2011 at Afnor in Paris. Erik Büthker from Holland was elected president

while Charles Pierre Bazin de Caix from France was nominated secretary.

Since then the group met eight times in total with the goal to formulate a

draft proposal by fall 2013. In total 10 meetings are planned with

additional focus group meetings, phone conferences and webinars.

Responsible organisms of 17 Countries participate in CEN TC408: Austria

(ASI), Belgium (NBN), Bulgaria (BDS), Czech Republic (UNMZ), Denmark

(DS), Finland (SFS), France (AFNOR), Germany (DIN), Greece (ELOT),

Italy (UNI), Latvia (LVS), Norway (SN), Slovenia (SIST), Slovakia (SUTN),

Spain (AENOR), Sweden (SIS) and the United Kingdom (BSI).

In addition there was an established liaison with seven EU organisations:

Afecor, EBA, Farecogaz, GIE, Marcogaz, ENTSOG and NGVA Europe.

Formal liaisons with other technical committees were established:

CEN/TC 19 on Gaseous and liquid fuels, lubricants and related products of

petroleum, synthetic and biological origin, CEN/TC 234 WG 11 on Gas

infrastructure/ Gas quality and ISO/PC 252 on Natural gas fuelling stations

for vehicles.

A number of stakeholders participated occasionally during the meetings:

Car manufacturers; grid operators; biomethane producers; fuel producers;

natural gas suppliers and manufacturers of gas fuelling stations.

The start was a little difficult for several reasons, the major being that the

mandate was not as clearly formulated as should have been, especially

concerning the job sharing or rather the definition of the responsibilities

between TC 234/WG 11 - M 400 and TC 408 – M 475.

3. Experts groups

In order to allow an efficient work three internal expert groups were

created within the framework of the TC 408:

• EG1: bio-content determination

• EG2: NG/biomethane as a fuel

• EG3: grid injection specification

• EG4: test methods

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3.1 Expert Group 1

A topic which gave reason to long discussions was the expectation of the

Commission as part of the mandate that a method should be developed or

reported allowing the determination of biomethane at any place in the

natural gas grid. It was expected that a C14 method would be applied. An

expert group (EG1) was founded to explore the possibilities.

After the first meeting, the expert group was in full agreement that such a

method would not be feasible at reasonable costs. In an expert discussion

paper it was highlighted that for full demonstration of biomethane various

measurement points along a given grid would have to be installed to follow

the biomethane flow continuously. Such equipment would cost in the order

of 1.5 m Euro.

Other methods to guarantee the mass (energy) balance between the

injected and the removed biomethane like certificates (guarantees of

origin) are proven, cost effective and even more precise. After several

meetings with Kyriakos Maniatis from DG Energy it was decided to describe

a method (as complicated and expensive as it is) for the potential case that

it would have to be determined for legal or contractual reasons close to the

point of injection. But at the same time an easy applicable control method

should be introduced.

3.2 Expert Groups 2 and 3

It was soon realized that it would probably not be possible to define an

equal standard for vehicle fuel and for grid injection. Therefore two

subgroups have been founded. The vehicle fuel group (EG2) is mainly

composed of car manufacturers and led by our project partner Jaime Alamo

from NGVA Europe. The other expert group (EG3) on grid injection includes

primarily the representatives of the national standardisation bodies, TSOs,

gas utilities and the associations. The group is led by Jacques Dubost from

GDF Suez. There is some interaction with EG2 in that the quality

requirements of the vehicle fuel should not be higher as for natural gas

because in next future the large amount of fuel will still be delivered by NG

and not by biomethane. In essence, TC408 is dealing with three major

cases: 1) Gas upgrading and grid injection with subsequent use in housing,

industry or as a fuel; 2) Upgrading without injection and use it as a fuel

either as a stand-alone fuel or as a blend e.g. with LNG; 3) Local

production and local utilisation with very specific requirements (Fig.1)

The challenge of the injection group is to find a common ground between

all the different national parameters. All parameters to be proposed should

therefore be based on sound measurements by standardized sampling and

testing methods. A first list of parameters was proposed for the further

discussion. An outline of the full table is given in Table 1.

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Fig. 1 Different cases of fuel specifications by TC408

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Table 1: Major parameters for grid injection (Source EG3)

In December 2011, EG2 came up with a first proposal for biofuel quality

parameters that served for further discussions (Table 2).

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Table 2. First proposal for parameters defining biomethane quality

(Source EG2)

The discussion on the lower heating value (LHV) has been narrowed down

to 44MJ/kg corresponding to 95% methane. This is a little bit lower than

the value in the German regulation DIN 51624 of 46 MJ/kg (Fig. 2).

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Fig.2 LHV Relation for a binary mixture of CH

4 and CO

2

(Source: E.ON Ruhrgas)

4. Open points to be discussed

A number of points are still open for discussion either because reliable data

are still to be compiled or because the relevant data are not available yet

and must be part of future research projects:

- Sulphur

- Siloxanes

- Trace components that may (or can) have an effect on health

- Exposure models for these trace components

- Oxygen

- Hydrogen

- Methane number (parameter linked to the risk of knocking in

engines, cf. octane number for liquid fuels)

In the case of insecurity preliminary figures will be used in the standard

that will subsequently be adapted. There is still dispute if these values will

arbitrarily be set at a low value and weakened afterwards if possible or if

they should be set at the upper limit of known band width and

subsequently be reduced if necessary.

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4.1 Hydrogen Sulphide

ECE R110 sets a limit (for safety operation of Natural Gas Vehicles) of 23

mg/m3 and the German DIN 51624 sets 7 mg/kg.

The requirements for the limit of the H2S concentration are quite different

depending on which client the participant is representing:

Volkswagen requests a sulphur limit of max.10 ppm in CNG. Their

argument is that petrol and diesel fuel already are at a limit of 10 ppm

sulphur. The limit is dictated by the under-floor catalysts which cannot

recover from high sulphur contents at low temperatures.

Bosch promotes a North American study which proposes some 3,5 - 7

mg/kg limit due to the H2S combustion products sticking ICE valves.

ACEA also asks for a limitation at 10ppm in fuel where as TC234/WG11

could accept 20mg/m3 in the grid.

The Netherlands have experience with a H2S content of natural gas

delivered to the domestic market of close to zero and always lower than 5

mg/m3 whereas in Italy that H2S in their network code is a value below 6.6

mg/m3 (m3 at 1.01325 bar and 288 K).

The biomethane producers promote a value not lower than 10ppm.

The current discussions in TC 408 tend towards 5 to 10ppm.

4.2 Siloxanes

Siloxanes might create serious problems in engine pistons (Fig.3) and

especially in micro-turbines. When siloxanes are oxidized, silicium oxide is

formed that covers surfaces leading to abrasion or even blocking of

engines. Siloxanes are mainly a problem in biogas coming from landfills

and sewage sludge digestion. Main sources are sanitary products

(maquillage, tooth paste, shaving foams, etc.), foam from fire

extinguishers, lubricants, etc. The German delegation reported, through its

Bosch representative, of tests studying the impact on lambda sensors

claiming the need for a total silicon content below 0,06 mg/kg. The main

reported problem is linked to the effects of silicon glass layer covering the

active electrodes of lambda sensors and creating malfunction in the signal

to be transmitted, plus a potential deterioration of the catalytic active

platinum-based electrodes

Standard procedures in Austria and Switzerland are active carbon filters to

remove the siloxanes. If low values have to be achieved, cooling down to

-25°C is necessary.

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Fig. 3 Silicium Oxyde (SiO2) formation on engine pistons and piston

blocks

Several documents have been made available by different experts. Limits

are depending on the application but the most strict ones for gas turbines

and ICEs (ranging from 0,05 mg/Nm3) up 2mg/Nm3 for gas engines.

There is still no agreed sampling and test method available yet. DNV KEMA

has presented a project proposal to the EC for engine testing and GERG is

willing to work in the sampling and test methods.

4.3 Water dew point

Water content/water dew point: as both parameters are important and are

also correlated (ISO 18453) CEN TC408 decided to limit only one of them,

and preferably the dew point (Fig.4).

Fig. 4 Water dew point in function of water content and pressure

The proposal under discussion is to create a variable limit depending on the

different climate zones:

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Zone A: 0 0C at 200 bar

Zone B: -10 0C at 200 bar

Zone C: -20 0C at 200 bar

Zone D: -30 0C at 200 bar

The duty of the national regulators is to specify to which zone they belong

4.4 Methane number

Methane Number is the measure of resistance of fuel gases to engine

knock (detonation) and is assigned to a test fuel based upon operation

in a knock testing unit at the same standard knock intensity. Pure

methane is assigned as the knock resistant reference fuel with a methane

number of 100. Pure hydrogen is used as the knock sensitive reference fuel

with a methane number of 0.

Gas Infrastructure Europe (GIE) is an association representing the sole

interest of the infrastructure industry in the natural gas business such

as Transmission System Operators. They are against the introduction of

a methane number mainly for two reasons:

1. A Methane Number of 80 as recommended by Euromot (the

European Association of Internal Combustion Engine Manufacturers) would

endanger the Security of natural gas supply to the European market,

limiting acceptable gas sources (e.g. from LNG).

2. Including the Methane Number in the European Standard

requires an agreed and reliable method of determination and should

incur minimum costs.

The methane number ( M N ) is not a thermodynamic property of gas,

so no Equation of State (EOS) can be used to calculate it. Moreover,

there are different calculation methods available and the results are

different depending on the method applied as listed below:

- Linear Correlation method

- Hydrogen/Carbon (H/C) ratio method

- AVL method - AVL Inc. developed a method to calculate the methane

number, based on experimental measures of different gas mixtures (up to C4, H2, CO2 and H2S). Property software is available to purchase

which uses proprietary algorithms to determine the Methane

Number, but does not take into account all components.

- E.ON- gas calculation

- Calculations of various engine manufacturer methods

Euromot asked for a Methane Number between 80 and 100 which would

exclude the majority of available LNG from coming to Europe (Fig.5). The

argument of Euromot is that a methane number below 80 would reduce

the efficiency of modern gas engines (Fig.6).

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Fig.6 Methane Number versus Wobbe index of imported LNG

Fig. 6 Example of efficiency of gas engines (CHP) with different methane

numbers

A Methane Number of 80 would endanger the Security of natural gas

supply to the European market, limiting acceptable gas sources. For

example, Denmark has been supplied with natural gas with a

methane number around 70 (AVL method) from the Danish part of the

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North Sea for more than 20 years. The span of variation is typically

from 65 to 75, all of which would require further processing or

curtailment if the gas standard required a Methane Number above 80.

Gassco has also expressed its concerns about the inclusion of the Methane

Number since it may affect Norwegian gas exportations.

As mentioned before, the inclusion of a Methane Number in the

European Standard requires an agreed and reliable method of

determination and should incur minimum costs. There is no commonly

agreed Methane Number calculation method today:

- The only methods to calculate Methane Number included

in an international standard do not correctly predict the

trend of the Methane Number when hydrogen is injected.

- Current methods do not take into account the presence of

hydrocarbons heavier than butane.

- Some methods to calculate Methane Number (e.g. AVL)

require the purchase or development of property software in

order to be used effectively.

ACEA and car industry is opting for a methane number of 70 (AVL method).

This corresponds also to the engine test fuel.

4.5 Oxygen

There is a large variety among the different countries in the allowed

oxygen content from 0.1% up to 3% (Table 3) whereby the 0.1 correspond

already to a 10 to 100 fold increase in France, the UK respectively in Spain.

For the general NG grid specification, CEN/TC 234 is proposing to make it

variable depending on aspects such as proximity to underground storages,

though the limits are still to be discussed. For biomethane injection into the

grid some preliminary values ranging between 0,1 and 2% have been

proposed.

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Table 3: Oxygen limits in the different countries