Standardization of biomethane WP3 / D

Transcription

1 Standardization of biomethane WP3 / D The sole responsibility for the content of this publication lies with the authors. It does not necessarily reflect the opinion of the European Union. Neither the EACI nor the European Commission are responsible for any use that may be made of the information contained therein.

2 Authors: Dr. Arthur Wellinger Contact: European Biogas Association Rue d Arlon Brussels 2

3 Content 1. Summary of achievements Introduction The mandate and working groups of CEN TC Experts groups Expert Group 1: Bio-content Expert Groups 2 and 3: Grid injection and vehicle fuel Expert Group 4: Siloxanes/total silicon Other parameters Discussion on dust and microbes Carbon Dioxide Oxygen Methane Number (MN) Peak and mean values (off-spec management) Limit values for contaminants in biomethane based on health assessment criteria Parameters and limit values Part 1: Specifications for biomethane for injection in the natural gas network Part 2: Automotive fuel specifications Further evaluation

4 1. Summary of achievements Standardization of biomethane was one of the important drivers for the formulation of the Green Gas Grids project. It was planned to carry on work of the former EU project Biogasmax and of the technical association of the gas industry, Marcogaz. When a few months after the start of GGG a mandate was given to CEN to develop standards for biomethane for use in transport and injection in natural gas pipelines it was decided to collaborate intensively with this group (TC 408) instead of trying to create an own, hence unofficial standard. The GreenGasGrids partners NGVA and EBA were further involved in developing standards bringing the practice aspects of the biomethane producing industry and the car industry into the expert group TC 408. The work for a draft of the Standards took about 2.5 years including 11 meetings. The progress of the work was reported to GGG members and interested groups through discussion papers and a workshop in 2013 dedicated to the topic. Within the next few weeks the draft will go into consultation by the gas industry and external experts. It is expected that it will take another 5 to 8 meetings until the end of 2014 before the final standard can be published. A number of parameters (like oxygen) that were discussed had already effect on national standards that were adapted correspondingly. For some other parameters (like siloxanes) indicative values were given in footnotes only because there was not enough scientific evidence. Corresponding research project are under way or have been initiated. 2. Introduction By the end of 2012 biogas was upgraded to biomethane in eleven European countries. In nine countries thereof biomethane was injected into the grid. Sweden and Switzerland have the longest experience, which started back in the early 90ies. All of the biomethane producing countries developed national standards for injection (plus some more countries not injecting biomethane yet) 1. However, all of them use different parameters and/or concentrations of compounds (other than methane) with large variations up to a factor of 100 (oxygen). In recent years, two projects have tried to develop common standards for injection. During the FP6 project Biogasmax a proposal was developed 2 which wanted to find a compromise between stringent parameters created by the national DSOs and parameters that could be achieved at reasonable costs and process energy consumption. Another approach was made by Marcogaz, a technical association of the gas industry. Their report was used as the starting point for the work of the standardization work of CEN/TC234/WG9. 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. Nevertheless, as part of the work the CEN working group reached out the European Commission for assistance, which together with other efforts made the EU 1 Marcogaz (2006). For a more recent update, please refer to the GreenGasGrids report Technical stands for biomethane as vehicle fuel and for injection into the natural gas grid technology _0948_ pdf 4

5 aware of the lack of biomethane standardisation, resulting in the issuing in 2010 of mandate M/475, Mandate to CEN for standards for biomethane for use in transport and injection in natural gas pipelines, the starting point for the current standardization work on biomethane within CEN (Comité Européen de Normalisation). The intention of mandate 475 was to allow one standard for each application, with the natural division being that CEN/TC 234 Gas infrastructure dealt with injection, while CEN/TC019 Gaseous and liquid fuels, lubricants and related products of petroleum, synthetic and biological origin would take charge of the fuel standard. However, this was opposed by many natural gas grid operators, which delayed the start of the work a full year. The compromise was to make a joint technical committee, an independent project committee with its work limited to the one of the mandate: CEN/TC408: Project Committee Biomethane for use in transport and injection in natural gas pipelines. Both TC 234 and TC019 were allowed to nominate experts and liaise with TC408. While formulating the GGG project, discussions were ongoing that these two existing CEN groups would take responsibility for the carrying out of the mandate from the European Commission. 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 is directly involved with IEA Bioenergy Task 37 work, acting in the agreement as Technical Coordinator. The link to the (completed) Biogasmax project is also granted because Arthur Wellinger was responsible project partner of the Swiss partner Berne. As such he was co-author of the recommendations for injection parameters. Shortly after the beginning of the GGG project the EC decided to entrust the mandate 475to the before mentioned new CEN technical group (CEN TC 408) to develop standards for both biomethane as a fuel and for injection to the grid. At that stage GGG decided to fully collaborate with this group under formation. This was possible because two project partners, EBA (represented by Arthur Wellinger) and NGVA Europe (represented by Jaime del Àlamo), had the right to participate in the TC as specialized European associations. However, the development of the standards remained an important part of GGG in the discussions during each GGG meeting and especially during the workshops alongside the meetings held in Brussels, Warsaw and Zagreb. The workshop in Paris in March 2013 was fully dedicated to the information and discussion of the biomethane standards. The proceedings and contributions of the workshop are available on the projects website ( Further, a discussion paper has been written on the subject of Technical standards for biomethane as vehicle fuel and for injection into the natural gas grid 3 " that can be found on the same website. In addition, numerous mails were exchanged and some phone conferences held between the project partners and the directly connected experts of NGVA and EBA involved in CEN TC/408 in order to protect the feasibility of biomethane production from biogas. 3 eengasgrids_project/ggg_discussion_paper_technical_standards_2013.pdf 5

6 3. The mandate and working groups of CEN TC408 In 2011 CEN was given the mandate to elaborate 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). This standard was prepared by CEN/TC 408 in response to the European Commission standardization mandate M/475. It should be noted that M/475 is linked to M/400 (2007), the mandate on standardization work on natural gas quality entrusted to CEN/TC234/WG 11, pren XXX Gas infrastructure Quality of gas - Group H. Mandate 475 stipulates that the parameters and limits adopted by WG11 should be taken over and referred to by TC408. The European Standard on biomethane was not to include unnecessarily restrictive requirements, as long as the proper functioning in the intended applications can be guaranteed. 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". Because the biomethane quality for vehicle fuel is closely related to the quality of natural gas 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. This was accepted by both CEN/TC019 and CEN/TC234. The OEM industry was in strong favour of this, since the current international standard for CNG, issued in 2006, ISO Natural gas Natural gas for use as a compressed fuel for vehicles, is lacking quantitative regulation. The scope of CEN/TC 408 encompasses 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. Until the 3 rd December 2013 the group met eleven times (instead of the planned 10 meetings) with the goal to formulate a draft proposal towards the CEN committee by end of Besides the plenary meetings additional expert group meetings, phone conferences and webinars were organised. Responsible organisations of 17 Countries participated in CEN TC408: Austria (ASI), Belgium (NBN), 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), Switzerland (SVGW) 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. The group was growing over time and included also the OEM industry (Volvo, Scania, VW and Bosch), one major oil company (Exxon Mobil) and the Association of manufacturers of gas utilities. 6

7 Formal liaisons with other technical committees were established: CEN/TC 19, CEN/TC 234/WG 11, ISO/PC Experts groups In order to allow an efficient work several internal expert groups were created: EG1: bio-content determination EG2: NG/biomethane as a fuel EG3: grid injection specification EG4: Siloxane concentration EG4: Exposure model 4.1 Expert Group 1: Bio-content 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 presented allowing the determination of biomethane at any place in the natural gas grid, i.e. keeping track of the bio-content in real-time. It was expected that a C14 method would be applied. An expert group (EG1) was founded to explore the possibilities. Very quickly, the expert group came to the conclusion 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 million Euro each. 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. 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. 4.2 Expert Groups 2 and 3: Grid injection and vehicle fuel 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 was led by our project partner NGVA Europe (represented by Jaime del Àlamo). The other expert group (EG3) on grid injection included primarily the representatives of the national standardisation offices, TSOs, gas utilities and the associations. The group was led by Jacques Dubost from GDF. 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 supplied by NG and not by biomethane. 7

8 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 was to find a common ground between all the different national parameters. All parameters to be proposed should therefore be based on sound measurements by standard methods. The challenge of the automotive fuel group was to find a way to meet the request of more strict requirements from the OEM s, while still allowing for the rather wide specification of natural gas, developed by WG11, to be applicable. Fig.1 Representation of some flows and uses of biomethane and natural gas 4.3 Expert Group 4: Siloxanes/total silicon Siloxanes are linear or cyclic compounds composed of silicium and oxygen as their major constituents (Fig. 2). It is reported that the use of siloxanes (organic silicon) is increasing in household industrial cleaning products and personal care products. Most siloxanes are 8

9 very volatile and decompose in the atmosphere into silanoles, which are eventually oxidised into silicon dioxide. Some siloxanes end up in waste water and are adsorbed onto the extracellular polymeric substances of sludge flocks. Siloxanes are volatilised from the sludge during anaerobic digestion and end up in biogas. Silicones are also sometimes added in digesters as anti-foaming agents, where they can biodegrade into siloxanes. Figure 2. Basic structure of linear and cyclic siloxanes Organic silicon compounds end up in landfills from sources such as shampoo bottles and other containers in which some of the product remains, through landfilling of waste water treatment sludge and from packaging and construction material. Silicon impurities need to be removed during upgrading of biogas to biomethane. During combustion of biomethane, siloxanes and other organo-silicon compounds form silica which generates deposits, e.g. on valves, lambda oxygen sensors and cylinder walls, causing abrasion, exhaust gas misalignment or blockage of pistons and cylinder heads, respectively. In particular vehicle engines and gas turbines are affected by residual silicon contamination in biomethane. Vehicles with spark ignition engines are developed for fuels, e.g. gasoline, gasoline ethanol blends and natural gas which all are literally free of silicon. The absence of silicon impurities enabled the use of lambda oxygen sensors in front of the catalyst for exhaust gas control. Deposition of silica on sensor elements impedes oxygen diffusion. Engine applications with switching type sensors require less than 0.1 mg silicon/kg biomethane. Higher silicon contents misalign oxygen sensors and reduce their durability. Far better suited are wide band sensors taking concentrations of more than 1mg silicon/kg biomethane. Another option is to allow for earlier replacement of the oxygen sensor, during regular service. The OEM component manufacturers object of course, due to increased cost (about 20 /part!). On the other hand, if siloxanes contents are very stringent, cost of removal during upgrading increases far more. Gas combustion turbines are also vulnerable to silica. By the high velocity of the gas streams hard particles cause erosion or build up deposits. Seizure is reported, when larger chunks of silica break off. Some turbine manufacturers also request silicon contents below 0.1 mg silicon/m³ biomethane. European Metrology Research Program Presentation. Characteristics of energy biogases. Test Methods: There was a large EU analysis project allowing to develop analysis methods that could be available for all future EU projects and thus make results comparable between the different projects. The Programme started back in 2007 with a total funding of 400 M. The main focus was the work on European metrology R&D to facilitate integration and exchange between national research programs. 9

10 A schematic of the project s structure can be found in Figure 3. Figure 3: Structure of metrology research program A specific sub-program on Siloxanes was also ran by VSL and NPL where they worked on new methods for siloxanes/silicon determination (GC-FID, GC-MS & GC-AED) and different validation and stability tests are still on their way. They claim their proposed method (ICP MS) to be different from the ones proposed by SP in Sweden 4 as those are based on Tenax Tubes. Via the ICP-MS method, a total silicon determination would be feasible. For more details, Dr. Andrew Brown from the UK NPL should be the contact person: andrew.brown@npl.co.uk A number of analysis data was collected by CEN TC 408 members to estimate the relevance and potential reduction during upgrading of the siloxanes in biomethane. The highest values in France were found in the raw gas of sewage sludge digestion in waste water treatment plants (WWTP) with total siloxanes values of up to 400mg/Nm 3 biogas (Fig.4). Most values ranged between 30 and 60mg/Nm 3. In two group internal reports it was shown that after upgrading of biogas from agricultural and food waste digesters with different technologies siloxanes values dropped as low as 0.3 mg/nm 3. Figure 4 shows the ranges of siloxane values in raw gas and biomethane in comparison to user specifications and guarantee values. 4 SGC report 243: K. Arrhenius, B. Magnusson, E. Sahlin SGC Rapport 243 Föroreningar i biogas: Validering av analysmetodik för siloxaner (2011) 10

11 Fig.4 Siloxane concentrations of measured and warranted values (logarithmic scale) In the Swedish study mentioned above average total silica values in WWTP of 14.4 mg/nm 3 (N=7) where found which is comparable to a German study with an average of 14.9 mg/nm 3 (N=308). The raw gas from wastewater treatment plants in Sweden contained significantly more siloxanes than the raw gases from landfills and from anaerobic digestion of agricultural residues (Fig. 5). It is however pointed out by SP that the no. of samples is a bit too low to draw any general conclusions. Since the beginning of the mandate the Technical Committee knew that there would not be enough data available to come up with a firm peak value for siloxanes in the biomethane. KEMA DNV therefore formulated a research project that was granted by the EC. However, the project start was delayed until the beginning of Therefore, the general view of the committee is still that the knowledge level is too low to be able to propose a scientifically based limit value. 11

12 Figure 5: Average for total silica (mg Si/Nm3)in raw gases from different substrates and in upgraded gases, together with maximum-minimum range of measured levels 5. Other parameters 5.1 Discussion on dust and microbes During several meetings the potential danger of micro-organisms in the biomethane was discussed. Some of the gas experts expressed strong fears of pandemics due to dangerous bacteria or viruses in the gas. Even the results of several extensive research projects in Sweden and France showing that biomethane contained fewer microbes than natural gas could not fully convince them. However, the majority accepted the data. The fact that a dedicated dust filter with a nominal mesh size of less than 1 micron can be placed as close as possible to the injection point and according to new research data of Kema DNV remove also microbes, convinced also the hesitant ones. The operation of the filter should not be impaired by water, oil or hydrocarbon droplets. Such a filter also reduces greatly the content of biogenic material such as microorganisms. Smaller mesh provides better efficiency but increases the pressure drop across the filter. A HEPA type filter has a low pressure drop in proportion to its separation efficiency. A Dutch study showed that filters with an efficiency of at least 99,95% ( µm) are efficient enough to reduce the risks of micro biological contamination of the gas. 5.2 Carbon Dioxide Next to methane, carbon dioxide is the largest fraction in biogas. CO 2 is not a problem when biogas is used as vehicle fuel because it reduces the knocking characteristics at high pressure injection but it contains no energy and reduces the energetic volume of gas 12

13 bottles. Therefore it has to be removed. For grid injection it is mandatory to remove CO 2 in order to adapt to the standards of natural gas. It was agreed that at network entry points and cross border points between CEN member states the maximum mole fraction of carbon dioxide shall be no more than 2.5 % mol/mol. However, at entry points where the gas entering will not flow to another member state s system through a cross border point, a higher National limit of up to 4 % mol/mol may be applied, provided that the network is dry and not connected to installations sensitive to higher levels of carbon dioxide, e.g. underground storage systems. The current practice for injection of biomethane to local L-gas distribution grids is that higher contents of carbon dioxide in biomethane are allowed. The reason for this is that for L-gases a relative high content of inert gases is needed to fulfil the local requirements for the Wobbe number and the calorific value. Carbon dioxide is a by-product of the upgrading process and therefore it is relatively easy and cheap to add this gas to biomethane at the production site. For cost reasons carbon dioxide is mostly preferred to the addition of nitrogen. However, it is known that the addition of carbon dioxide enhances flame lift-off. The allowance of higher carbon dioxide content to the local L-gas distribution grid may therefore be associated with an increase of the lower Wobbe number limit, in order to prevent the risk of flame lift off. 5.3 Oxygen At the start of the CEN TC 408 work the national limitations for oxygen in the natural gas grids were far apart from each other with extremely low allowed concentrations in Spain (0.01%) and UK. The usual content of O 2 in raw biogas can vary between 0.1% and 3%. The fact of almost doubling this percentage when upgrading has to be taken into account. On the other hand, the possibilities of O 2 removal in upgrading processes are inexistent. Apart from the usual content of O 2 in biogas, the actual situation of biomethane injection in Europe should be considered: In the case of dry gas, values of 0.5% molar are accepted in several European countries (e.g. Switzerland, Sweden, The Netherlands) reaching up to 3%. In case of wet grids and cavern storages, the required levels decrease significantly, down to % when gas is to be stored in caverns. Countries with lower limits are studying and revising these values (Spain, France, UK, and Germany). The recommendation of the Biogasmax project was 3%. 5.4 Methane Number (MN) The combustion behavior of natural gases is of particular importance in internal combustion engines (e.g. co-generation systems, natural gas vehicles). A key property is the methane number (MN). It describes the knock behavior of fuel gases and strongly depends on the specific gas composition. MN is comparable to the octane number for gasoline. MN expresses the volume percentage of methane in a methane/hydrogen 13

14 mixture which, in a test engine under standard conditions, has the same tendency to knock as the gaseous fuel to be examined. High MN means high knock resistance; high knock resistance, in turn, means the possibility to design high compression ratio engines or higher boost curves in supercharged engines when running on natural gas and biomethane, hence good combustion, high efficiencies and thus low CO 2 emissions. If MN is too low, knocking may cause engine damage (if no knock control unit is installed) or lead to losses in efficiency and performance if engine operation has to be adjusted to avoid knocking combustion. Methane is the main constituent of natural gas and has high knocking resistance. The MN of pure methane is 100 while the MN of hydrogen is 0. Increasing fractions of higher hydrocarbons (ethane, propane and, in particular, butane) reduce knock resistance; inert components such as carbon dioxide or nitrogen increase knock resistance. There is no standardized or harmonized calculation method for determining the MN. It is envisaged to specify a standard method on international level (CEN, ISO) taking into account research results still outstanding. Gas engine manufactures have noted that the AVL method which is the method most frequently used in Europe developed in the late 1960ies, is not accurate enough for modern gas engines and therefore they have partly developed their own more precise calculation method (MWM). Table 1 lists the MN and other combustion characteristics for typical natural gases and biomethane. Table 1: Gas qualities of different natural gases (pipeline), LNG and biomethane with calculated MN (reference temperatures: 25 C superior calorific value; 0 C) EUROMOT, the European car industry association pushed a MN of min. 80 because at lower MN engines would lose efficiency with an increased emission. Nevertheless, if the engine is optimized for a MN of 70 from the beginning than the decrease of performance is negligible (Fig.6). 14

15 The span of MN number in European gas grids is typically between 65 and 75. Any increase to MN of min. 80 would lead to tremendous cost for upgrading and could reduce the gas availability because the increasingly imported LNG usually has a lower MN. Currently, the share of the grid volumes with an MN below 70 is marginal. It should also be noted that the gas business is very interested in making it possible to add renewable hydrogen to their networks, in order to make them greener. With a stricter level of MN 70, this would be much harder to achieve. Figure 6: Engine performance versus methane number (Source: Klaus Altfeld, Eon-Ruhrgas) 5.5 Peak and mean values (off-spec management) The definition of mean and peak values is extremely important for biogas installations where gas quality and therefore also the quality of the upgraded biomethane might vary considerably in function of the substrate digested. An expert group collated regulations and warrantee values from a number of different European countries and manufacturers of upgrading plants. Each European country has its own experiences and rules with or without market growth perspectives. More than half of the about 250 biogas upgrading and injection plants in Europe are operated in Sweden and Germany. They have also the most elaborated and detailed standards and rules (SS resp. DVGW 260). Other countries have none or only few plants in operation, thus little experience but in contrast more stringent rules, for example: France: Off spec situation induces cut off after 2 consecutive measurements exceeding the limit values (i.e. after 400seconds), Spain: limit values are instantaneous, even though there is a time period agreed between the biomethane producer and grid operator to fulfil requirements in case of off-spec situation 15

16 Throughout Europe there is a whole range of rules on how to manage disengagement of grid injection: warnings/alarms when peak limit values are exceeded with/without timely delay before shut down on the one end or rules for shut-down based on mean values over an hour or even a day. The expert group recommended to base shut-downs on an average value of minimum 1 hour or even better 1day. This would be in line with other requirements for air pollution control e.g. for combustion according to corresponding EU Directives. A lag period between 30 minutes and 2 hours is common in environmental industry allowing plant operators to take measures after the first alarm before the grid injection is shut-down. The reason for an alarm might be a failure of a gas analyser. A short-term automatic shut-down should be avoided in these cases. No doubt there is a need for accredited equipment, standardized protocols or guidelines and periodic control. The Swedish and German regulations distinguish between a warning and an alarm concentration with different allowed reaction times in function of the chemical parameter. An example of the Swedish agreement between E.ON Gas Sweden and the TSO Swedegas for a number of parameters is given in Table 2. Table 2. Warning and alarm levels with shut-off times in the Swedish agreement 16

17 5.6 Limit values for contaminants in biomethane based on health assessment criteria Another approach to assess and derive limit values for contaminants in biomethane is based solely on considerations of potential 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. The calculation is based on a French model developed by AFSSET for natural gas that considers two pathways: a) Inhalation of unburnt biomethane released from a gas cooker hob prior to its ignition and b) Inhalation of contaminants or products of combustion of contaminants released whilst a gas cooker hob is in use. Some 120 potentially available compounds have been considered in the calculations. The acceptable concentration was compared to the maximum concentration of that contaminant observed in UK landfill gases, according to the UK Environment Agency database. The ratio of this maximum value to the derived acceptable value was calculated. Contaminants for which a ratio of less than 0.5 was calculated were removed from further consideration. This means that only contaminants that have been observed in biogases at a concentration of one half of the acceptable concentration are considered. A value of 0.5 assumes that upgrading of biomethane results in a doubling of concentration, i.e. almost all carbon dioxide and no contaminant is removed. Table 3: Parameters and limit values recommended according to AFSSET model 17

18 Screening (i.e. calculation) of different relevant chemical compounds resulted in the specification shown in Table 3. The exposure model was heavily discussed because the Italians didn t agree to the French model applied. For example with the French model the value for CO would be 3% and with the Italian model the value would be 0.1%. Because there was no agreement an expert group was formed. Step 1: Expert group on health criteria resulting in values (exposure model accepted by EG) Step2: With the limit values it should be evaluated if the grid integrity, etc. is guaranteed Step 3: Evaluation of other criteria like water protection, engine performance, consumer acceptance 6. Parameters and limit values 6.1 Part 1: Specifications for biomethane for injection in the natural gas network After all the discussions and with the increasing resistance of the car manufacturers and some mostly gas experts inexperienced with biomethane it became clear that apart from long informative annexes not many parameters can be firmly defined for grid injection of biomethane (Table 4). For binding definitions of a number of additional parameters, the series of evaluations and research projects started within CEN TC 408 still have to be finished. Another series of parameters that initially had been heavily debated in CEN TC 408 had to be defined by CEN TC 234/WG 11 working on natural gas pipeline specification. They started work before CEN TC 408 and are therefore ahead in the development of standards. They launched the internal consultation in the second half of 2013 and have received over 600 comments until end of November. The parameters under discussion included the following peak values: Methane number > 65 (according to MWM model) Total sulphur < 20mg/Nm 3 (not odorized) Odorization will remain a national decision H 2 S+COS < 5mg/Nm 3 Mercaptane < 6mg/Nm 3 Carbon dioxide cross border 2.5% for inland 4% Water dew point: -8 C at 70 bar Hydrocarbon dew point: 3 C 18

19 The Wobbe index is still discussed because it is a national standard and all boilers are built according to the national Wobbe index. If the Wobbe index exceeds certain ranges, carbon monoxide might be emitted. The proposed range is about + 7% around the average Wobbe index, boiler manufacturers want to reduce it to + 2%. Most of the data are not scientifically based but more on experience. There were intense discussions with LNG importers because they have very low and depending from the origin, variable methane numbers. 6.2 Part 2: Automotive fuel specifications This standard specifies the requirements and test methods for natural gas, biomethane and blends of both at the point of use as automotive fuels irrespective of the storage state (compressed or liquefied). LNG or liquefied biomethane has to be re-gasified prior to testing. 19

20 Table 4: Parameters and limit values for grid injection of biomethane (H-grid) 20

21 Table 5 Requirements, limit values and related test methods for natural gas and biomethane as automotive fuels SeeTable 6 21

22 The requirements on the water dew point are very sensitive to the climatic conditions of the countries they are being applied. The functionality of the refueling stations and the drivability of the gas powered vehicles rely on the water level being so low that no hydrocarbon hydrate precipitation occurs. Three classes, A, B and C are therefore given to allow for climate dependent limits to be adopted nationally. In a national annex to this European Standard, each country shall indicate which class(es) it adopts. Table 6: Climate dependent requirements and test methods 7. Further evaluation The preliminary text of the two parts of the biomethane standard has been sent to the TC 408 participants and CEN partner countries for consultation. The duration will be 6 months. Partners of GGG are welcome to send their comments to the author of this report who will report them further to the CEN TC 408. The committee will meet another four times in 2014 to discuss and incorporate the comments made during consultation. It might be even more efficient to get in contact with the national entity which is part of the CEN group to place remarks. The author would appreciate to receive copy of the corresponding discussion. 22