REDUCTION OF METHANE EMISSIONS IN THE EU NATURAL GAS INDUSTRY Jürgen Vorgang, E.ON Ruhrgas AG, Germany; Angelo Riva, Eni S.p.A, G&P Div. G&P, Italy; Alessandro Cigni, Marcogaz, Belgium; Daniel Hec, Marcogaz, Belgium Keywords: Methane emissions, methodology, emission factor, best practice 1. Background Global climate change led to an intensive discussion about greenhouse gases. The most important anthropogenic greenhouse gas is carbon dioxide (CO2), but other emissions also contribute to the greenhouse effect. Burning of fossil fuels to provide energy and heat is recognised as a significant source of greenhouse gas emissions. Natural gas has a growing role in energy and heat production because it is recognised as the fossil fuel with the lowest specific CO2 emissions per unit of energy provided. But its principal component, methane (CH4), is the second important anthropogenic greenhouse gas, which has a global warming potential 25

1 times that of CO2. In terms of climate change effects, burning natural gas is

better than releasing it into the atmosphere. Compared to oil or coal the life cycle analysis regarding CO2 equivalents for natural gas from production to the customer in the EU is better. Greenhouse gas emissions of natural gas from the European transmission, storage and distribution systems have been recognised for some time by Marcogaz, the Technical Association of the European Natural Gas Industry, as a subject to study. One of the standing committees of Marcogaz is the Joint Group Environment, Health & Safety, led together with Eurogas. The question of how methane emissions are determined in the member countries led to the founding of a working group “Methane Emissions”, in which members from 9 different EU countries

2 took part

to share their experiences. The final results of this working group were internal reports describing

• A methodology for estimating methane emissions in the gas industry

• Guidelines for choosing methane emission factors The working group is aware of the fact that this is a first approach to support companies in building up an inventory of releases and to start communication for a better comparability. In the given framework of this working group it was not possible to verify the emission factors. A report on “Reduction of methane emissions in the European gas industry – Practices and technologies” containing a number of case studies adopted by European gas companies to reduce methane emissions has also been prepared by the working group and has been published on the Marcogaz website.

3

This paper shows the efforts of the European gas industry in addressing methane emissions and provides best practice guidance for reducing methane emissions which other companies may learn from or which they can adopt. 2. Objectives of the Paper The objective of this paper is to give a short introduction to the Marcogaz-Eurogas study. Here the broader study covering different sectors of the natural gas supply chain will be limited to the transmission sector with special focus on the methodology for evaluating methane releases to the atmosphere. The main parameters are emission factors, which can vary from one gas company to another for various reasons. A proposal is made to recommend choosing emission factors within a range identified by the study. 3. Methodology 3.1 Conditions and Definitions The conditions for using a common methodology for different companies were defined as:

• Applicable to gas transmission, storage, distribution and LNG,

• Covering normal operations as well as routine maintenance, malfunction of the system and external factors, e. g. damage from excavators,

1 Mass-related, see IPCC Assessment Report 4, 2007

2 Austria, Belgium, France, Germany, Italy, Netherlands, Slovakia, Spain, UK

3 www.marcogaz.org

• Based on existing knowledge (no R&D required),

• Considering fugitive emissions, vented gas, incomplete combustion and pneumatic devices. Terms to be defined are as follows:

• Fugitive emissions are all small leaks from flanges, pipe equipment, valves, joints, etc. that are more or less continuous sources.

• Vented emissions can be distinguished as o intended vents for maintenance or operational reasons and o vents from incidents, when the content of the gas equipment is released to the atmosphere.

• Incomplete combustion emissions are unburnt methane gases in the exhaust gases mainly from gas engines, but also smaller amounts from gas turbines and combustion facilities.

• Pneumatic emissions are all emissions caused by gas operating valves and other devices, continuous as well as intermittent emissions.

3.2 Evaluation Basis The evaluation of some methane emissions is difficult because these emissions are very low in relation to the volumes of gas transported and because of a high number of emission sources, different operating procedures and different inspection intervals and time until repair. For these reasons it is in practice impossible to measure all the emissions exactly. Therefore the way to calculate methane emissions is based on the use of emission factors and activity factors with the following equation:

Emissions = Σ (Activity Factor x Emission Factor) The activity factors are the population of emitting equipment such as length of pipelines, number and type of valves, number and type of pneumatic devices, and the frequency of emitting events such as number of operating vents and frequency of operation of gas-driven pneumatic devices for pressure regulation. Activity factors can be determined by knowledge of the infrastructure and the operation (e.g. length of pipelines, number of valve stations and number of natural gas-operated startups of gas turbines). The emission factors are defined as the quantity of methane emitted from each emitting source and for each emitting event and period of time, respectively. Some emission factors can be calculated or measured, such as the gas vented for operating reasons or for maintenance, others can be evaluated on the basis of the characteristic of components, such as the emissions from each intervention of pneumatic devices, and others are very difficult to be evaluated or measured, such as those deriving from fugitive emissions. This equation can be used for fugitive and pneumatic emissions as well as for incomplete combustion. It is also applicable to the calculation of periodic vents, e.g. methane emissions caused by starting a turbine with pressurised natural gas. 3.3 Emission Factors On the basis of this calculation equation a spreadsheet for transmission, storage, distribution up to the meter and LNG was created to cover all relevant sources of methane emissions and make sure that all are systematically taken into account.

Figure 1: Spreadsheets for transmission, storage, distribution and LNG

These spreadsheets were circulated among the Marcogaz-Eurogas working group members coming from 9 different EU member states to determine how the emission factors vary from one company to another. Not all companies used this methodology and therefore they were not able to supply all factors, so sometimes the number of answers for an individual factor was low. The result was a high variability of emission factors (examples in Figures 2 and 3).

Figure 2: Emission factor for compressor station Figure 3: Emission factor for M&R station fugitive emissions fugitive emissions The working group investigated reasons for this variability:

• Sources of factors: The different factors were only partly based on measurements, but mainly based on estimations or literature data. The working group investigated the different approaches to measuring emissions. Some approaches are described in the literature. Common to all types of measurement up to now is the relatively high effort needed to get reliable results. The actual knowledge needs improvement, but due to increasing discussions about climate change and greenhouse gas emissions the tendency to take environmental reasons into account is growing.

• Equipment: Different companies in different countries are purchasing equipment according to national standards, therefore one can find a broad range of types of equipment within the companies. Thus, comparability does not exist.

• Groups of equipment: In some companies different sources were treated as one one group with only one emission factor, e.g. pipelines including valve stations or a complete city gate station.

• Age: Following the increasing use of natural gas as an energy source the development of technology has improved, so one can find different technical generations of equipment even within one company and of course in different companies in Europe.

The working group discussed many more different parameters like pipeline material for distribution pipes, maintenance and operating philosophy, location and, in some cases, pipeline ageing. The qualitative effect

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of parameters on the emission factor was estimated (see table in Annex I), but should be decided by each company individually. In the given framework of this working group it was not possible to verify the emission factors, so the values were all accepted as correct. A further investigation has been initiated, but needs more time to be undertaken. The dissimilarity of all those parameters among companies or among countries also makes the adoption of these coefficients a very tricky issue. To evaluate its individual methane releases, each company should use factors based on its specific conditions. Without knowing these factors, the working group proposes a range of emission factors, where each company using this methodology chooses its appropriate emission factor. The working group considers this proposal as a first approach, which shall be updated regularily with better knowledge of gas companies and of investigations on main influencing parameters with the aim of choosing appropriate emission factors.

Emission Factors

Marcogaz Range

Subsystem and Souce Type of Factor Minimum Maximum Unit

Pipeline System - Fugitive Emissions

Length of pipelines including valves, flanges etc.

0,8 107 m³/km/a

Pipeline System - Pneumatic Emissions

Number of valves with pneumatic operation

129* 129* m3/No./a

Compressor Stations - Fugitive Emissions

Mechanical power of gas turbines 450 6500 m3/MW/a

Compressor Stations - Fugitive Emissions

Mechanical power of gas engines 7800 97000 m3/MW/a

Compressor Stations - Fugitive Emissions

Number of blow down Valves 1850 35000 m3/No./a

Compressor Stations - Pneumatic Emissions

Number of valves with pneumatic operation

1106 3200 m3/No./a

Compressor Stations - Combustion Waste Gas

Fuel gas consumption turbines 0,001 0,954 %

Compressor Stations - Combustion Waste Gas

Fuel gas consumption engines 0,114 3,7 %

M&R Stations - Fugitive Emissions

Number of stations 5000 10000 m3/No./a

M&R Stations - Pneumatic Emissions

Number of stations 22300 24500 m3/No./a

M&R Stations - Combustion

Fuel gas consumption 0,0113* 0,0113* %

City Gate Stations5

- Fugitive & pneumatic Emiss. Number of stations 43 62 m3/No./a

*Only one value for this factor

Table 1: Emission factors for transmission – Range of values from EU member companies of the Marcogaz working group 3.4 Venting Venting, i.e. the release of unburnt natural gas to the atmosphere, is often caused by operational requirements (e.g. depressurising of a compressor), maintenance and repair measures, when working at the equipment requires a non-explosive atmosphere. Venting also might occur after third party interference, when e.g. excavation machines damage a pipeline. For the determination of vented volumes the above-mentioned equation cannot be used. In these cases the individual geometric volume of the vented sector of equipment must be calculated and the result is multiplied by the pressure of natural gas before venting. 4. Results of Data Collection

4 One extremely high value differs from most other very low ones

5 Depending on the national definition either part of transmission or distribution sector

The analysis of collected data from seven major western European gas transmission companies in 2004 shows similar distribution of emissions to the different sources of equipment (figure 4).

Pipeline System;

21%Compressor

Stations; 33%

City Gate

Stations; 3%

M&R Stations;

44%

Figure 4: Distribution of methane releases by transmission equipment

It was surprising that the releases form Metering & Regulating Stations have the highest share of emissions, whereas compressor stations and pipelines follow with a difference of 10 % each. In Figure 5 a more detailed view of individual reasons for releasing gas is shown.

Pipeline - Fugitive; 2%

Pipeline - Vents; 19%

Compr.Station -

Fugitive; 16%

Compr. Station -

Pneumatic; 4%

Compr. Station -

Vents; 12%

M&R - Fugitive; 17%

M&R - Pneumatic; 26%

M&R - Vents; 1%

City Gate Stations; 3%

Pipeline - Pneumatic;

1%

Figure 5: Distribution of releases in transmission in detail

On the other hand it was interesting to see the distribution of releases by kind of release (figure 6).

Fugitive

Emissions; 35%

Pneumatic

Emissions; 31%

Vents; 32%

City Gate

Stations; 3%

Figure 6: Distribution of methane releases by kind

It can be stated that fugitive and pneumatic emissions as well as venting are on the same level. Fugitive emissions are unintended releases, whereas pneumatic emissions and venting are caused by the technical requirements of the operator and the equipment in use. To reduce fugitive emissions it is important to identify the leaks responsible for the release and then take action to avoid them. To reduce other releases it is necessary to modify either the technology (reinvestment) or, if possible, the operating philosophy (e.g. keep compressors under pressure when taken out of operation). 5. Best Practice Cases To demonstrate that a lot of measures can be taken, a collection of best practice cases was made. Different companies offered their case descriptions to explain how emissions can be reduced or avoided. Each case study is combined with the name of an expert in the company together with contact details. The main items were:

• Flaring: Use of a mobile flare unit to burn vented gas at pipeline maintenance works.

• Reduction of maintenance emissions: Use of a mobile compressor to pump gas from a section to be vented into a neighbouring section.

• Reduction of operating emissions: Use of low or zero emitting pneumatic systems with re-use of the gas instead of venting.

• Inspection and maintenance programmes: Organisational measures to detect emissions earlier and stop them.

This report can be downloaded directly from the Marcogaz website

6. As the report produced by IGU Study

Group 3.3 of the Working Committee 3 for Transmission is based on the Marcogaz-Eurogas collection of best practice cases, any interested reader can also refer to that report. 6. Conclusions To determine methane emissions the companies have only a limited number of exactly measured data. Due to (still) high costs of measurements they usually use estimated or literature data instead. For companies it is a good starting point to use the recommended range of emission factors mentioned in the Marcogaz-Eurogas study unless they have a better knowledge about their individual emissions.

6 www.marcogaz.org – Marcogaz publications – Environment, Health & Safety – 2008 – “Reduction of methane emissions in the

European gas industry – Practices and technologies”

The variety of emission factors and their dependency on many influencing parameters require further investigations. A common approach has been adopted by some European companies to obtain a better knowledge of these influences. Preparing an inventory of emissions is a task which will be more and more important for the gas industry because scientific and public pressure to reduce greenhouse gas emissions will rise in the future. Due to the shorter lifetime of methane molecules compared to CO2, a reduction of methane emissions has a more rapid positive influence on the climate than reducing CO2. Various options are used to minimise emissions from the gas supply system for reasons of safety, economic considerations and operational efficiency. Against the backdrop of scientific knowledge about climate warming, the environmental consciousness of operators is growing. European gas companies have assumed technical and financial commitments to reduce methane emissions through the supply chain up to the customer's meter. It is the responsibility of individual system operators to approach this in the most cost-effective way, best suited to their particular circumstances, and taking full account of safety and security of supply. 7. Summary This report uses the previous work of the Marcogaz-Eurogas working group “Methane Emissions” to provide a baseline. It enables operators of transmission systems to evaluate their releases of methane to the atmosphere. A methodology is proposed to calculate emissions e.g. by the use of activity and emission factors. The paper proposes an interval for emission factors identified by European gas transmission companies as a first approach in case no better knowledge is available. Various options are used to minimise emissions from the gas supply system for reasons of safety, economic considerations, operational efficiency and environmental concerns. European gas companies have for many years been making a continuous technical and financial commitment to reduce methane emissions through the supply chain up to the customer's meter. Opportunities for reduction of methane emissions have been identified for a range of transmission and distribution activities and documented in a collection of best practice cases. Adoption of the methodologies and best practice cases should help to demonstrate that the proactive approach taken for decades limits the need for any legislation aimed at reducing methane emissions in the gas industry. Acknowledgement: The authors wish to thank the members of the Marcogaz working group “Methane Emissions” for their cooperation and contributions and especially Mr. Luciano Occhio from Snam Rete Gas S.p.A. for his support. Annex I: Qualitative influence of parameters on emission factors

Emission Factor

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Parameter

Age of the equipment

� � � � � � � � � � � �

Frequency of maintenance

� � � � � � � � � � � �

Time to repair � � � � � � � � � � � �

Time between 2 inspections

� � � � � � � � � � � �

Pressure in the equipment

� - � � � - - - � - - �

Diameter of pipe � � - - - � - - - � - �

Number of valves � - - - - - - - � - - �

Type of soil X - - - - - - - - - - -

Protection of the pipe

� - - - - - - - - - - -

Type of equipment

X x x x x x X x x x x X

Sealing quality � - � � - - - - � - - �

Operating philosophy

x x x x x x X x x x x x

Symbol Meaning

� the emission factor increases with the parameter

� the emission factor decreases while the parameter increases

X the parameter has an influence on the value but no trend can be defined

- there is no influence