Advances in greenhouse gas measurement, including fugitive methane

Better regulation of fugitive methane emissions is a high priority for the EPA and will significantly contribute to NSW achieving the objectives of its NSW Net Zero Plan. The EPA is seeking to investigate advances in the measurement of greenhouse gases (including methane) to improve the evidence base, better inform our regulatory approaches and improve tracking of the effectiveness of our interventions. As an early step in this journey, we commissioned the University of NSW to conduct a greenhouse gas survey across several suburbs in Western Sydney, an area that included licensed and unlicensed premises. The University of NSW is a specialist in greenhouse gas measurement and is furthering the development of techniques through their research programs.

Methane is a gas that is formed by natural processes and is the main component of natural gas. It is one of several gases including carbon dioxide, nitrous oxide and fluorinated gases that are greenhouse gases.

Methane can also be generated by industrial activity, for example venting of gas from coal mines and gas processing facilities, and surface emissions from waste facilities and sewage. These emissions are known as fugitive emissions.

Yes, methane is a greenhouse gas. Its global warming potential is estimated at approximately 28 times higher than carbon dioxide over a 100-year timeframe.

The aims of the survey were to:

• demonstrate how new greenhouse gas measurement techniques could be used to support the EPA’s regulatory functions
• identify unknown sources of methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) in the area surveyed, and
• potentially identify where more studies would be beneficial in the survey area to quantify the rates of emissions of methane, carbon dioxide and carbon monoxide.

The EPA’s long-term goal is to improve GHG emissions source identification, monitoring and measurement, to support improved mitigation and regulation of GHG emissions.

The survey was focussed on measuring methane concentrations. This is because methane is a potent greenhouse gas and sources of methane can often be reduced or eliminated, once identified. Methane reduction is a priority for the EPA as it is powerful greenhouse gas. Reducing methane emission in the short- to medium-term will greatly assist NSW achieve its net zero targets.

The instrument used to measure methane (Picarro 2401-m analyser) also has the capability of measuring carbon monoxide and carbon dioxide, which is why concentrations of these pollutants were also measured during the study.

To understand the survey results and what is considered a high concentration of methane, it is helpful to understand what ‘background’ or ‘fresh air’ concentrations are, as methane is a naturally occurring gas present in the earth’s atmosphere.

For the survey, baseline data was taken from Cape Grim, the north-western point of Tasmania. This location is used as a ‘fresh air’ reference point. The average concentration of methane during the month of May 2023 at Cape Grim was 1.868 parts per million (ppm).

Meteorological Organization Global Atmosphere Watch Programme’s recent (2022) measurement of methane levels from monitoring stations around the world show that the current average global background level of methane is 1.908 ppm.

The average methane concentration recorded during the study on 13 June 2023 was 2.272ppm, this is 0.405ppm above the Cape Grim (fresh air) background reference concentration. The Cape Grim background reference concentration was used only as a comparison for the methane concentrations detected during the survey. This elevated methane concentration recorded during the study is expected to be similar to concentrations found throughout Sydney due to natural gas releases (for pressure regulation and leakage) throughout the gas network distribution system and domestic and industrial point sources.

For comparison, methane concentrations must be between 50,000ppm and 150,000ppm before combustion can occur.

The term ‘significant’ was used to describe the size of the plume detected. For example, significant plumes were identified at around 1km or more, even if they contained relatively low concentrations of methane. ‘Significant’ does not refer to concentration levels, nor does it mean there are safety or health risks from the plumes.

The location has a mix of licensed facilities and unlicensed facilities, and the potential for unidentified sources of GHG emissions. The location was also within an area that is prone to odour complaints. Odours can be generated from the emission of landfill gas from waste management facilities, which in addition to odorous components, generally includes methane which is not odorous.

No. At room temperature and pressure, methane is an odourless and colourless gas.

A Picarro 2401-m analyser was used to measure concentrations of carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) on the evenings of 13 and 14 June 2023. Some areas were surveyed on both evenings. Some areas were surveyed on one evening only.

The survey has been useful in identifying that car-based technologies can be useful to inform further studies, regulatory support or interventions at specific sites.

While the study was focused on testing the technology, it did identify methane plumes of varying concentrations near five EPA licensed facilities.

As expected, the study found that concentrations of gases in the plumes were above background levels at the time of the survey, however, the emissions detected did not pose a health or safety risk for the community.

No.

Some facilities in the surveyed area are waste or resource recovery facilities. The EPA’s Environmental Guidelines for Solid Waste landfills (2016) (PDF 1.2MB) prescribes a methane threshold of >500 parts per million (ppm) which, if exceeded, would trigger further investigation and corrective action. Even though the methane emissions were above background levels, the methane emissions surveyed were well below this threshold.

As part of the EPA’s Climate Change Action Plan 2023-2026, Action 14 commits the EPA to regulating short-lived pollutants, including methane, emitted at licensed facilities.

No. 100% capture of fugitive methane and its destruction is not currently possible for landfills, especially older landfills which were not designed to efficiently capture landfill gas.

However, the EPA will be working with landfill operators to improve capture and beneficial reuse of landfill gas where appropriate, in accordance with best practice (where possible) in the short-medium term and over the longer-term as techniques improve.

No. The CO, CO₂ and CH₄ concentrations recorded at the time of the survey did not pose health or safety risks to the community.

The EPA is continuing to work with research institutions on a range of different monitoring technologies that can be used to inform the EPA’s regulatory response to climate change.

This study has shown great benefits in utilising monitoring technologies to identify and measure GHG emission sources. This can improve the evidence base, support further EPA action and interventions, and to assess the effectiveness of such actions and interventions into the future.

In relation to the specific GHG plumes identified in this report, the EPA has been working with some of the facilities to improve their gas management systems and to strengthen environmental performance requirements. Those measures include pollution reduction programs and licence variations and will also improve their management of greenhouse gas emissions. The EPA will continue to work with the identified licensees, as needed, to further investigate emission sources at their facilities, including methane emissions.