The resources sector works to minimise air quality impacts resulting from operations for the health of communities and the environment
Air quality can be impacted by emissions from a range of sources, including transport, industry, agricultural and urban activities. The resources sector contributes to these emissions and understands the need to minimise air quality impacts resulting from operations for the health of communities and the environment.
Dust is a key focus for communities and the Government due to the potential impact it can have on human health and amenity. Dust is small particles (also known as particulate matter), which come from a range of different sources. Dust can take a number of forms and sizes. For environmental and health purposes, dust is usually described by size:
- >PM10: Particle sized 10 microns in diameter and greater;
- PM10: Particle sized less than 10 microns in diameter; and
- PM2.5: Particle sized 2.5 microns and smaller.
PM2.5 and PM10 are invisible to the naked eye. For context, the below figure illustrates how small these particles are when compared with the size of a single thread of human hair or a grain of sand.
Source: United States Environmental Protection Agency (2018) Particulate Matter (PM) Basics
Larger dust particles (PM10 and greater) can be produced from many sources. In an urban area, PM10 results from lawn mowing, movement of plant material, tyre rubber and wind blowing over bare ground. For resource operations, PM10 or larger particles result from activities like moving rock and soil with large machinery or by blasting, traffic on haul roads or wind blowing over dumps and stockpiles.
In comparison, smaller dust particles (PM2.5) are generally produced from combustion processes such as vehicle exhaust, wood stoves and fires, which are present in all domestic settings. Whilst for resource operations, PM2.5 is primarily produced from vehicle and mobile equipment exhausts.
Dust can have a variety of health and amenity (nuisance) impacts depending upon the concentration, size of particles and the duration of exposure. Elevated levels of particles less than PM10 (including PM2.5) are of greater health concern than larger particles as they can reach the air sacs in the lungs. Whereas, amenity impacts are associated with PM10 and greater. These larger particles tend to settle out of the air close to its source.
Collectively, the total of all particles suspended in the air is referred to as Total Suspended Particulate (TSP) matter. When these particles settle out of the air they are referred to as deposited dust. Generally, deposited dust can include particles of any size, but often comprises particles larger than 20 microns in diameter (i.e. greater than PM10) that rapidly settle out of the air near its source (Qld Govt, 2017).
Air quality standards
The Queensland and Commonwealth Governments have set criteria for background (ambient) air quality, based on independent national and international studies, to ensure the ongoing health and wellbeing for communities and the environment.
At the Commonwealth level, the National Environment Protection Measure for Ambient Air Quality establishes standards for a range of emissions, including dust particles. These standards have been adopted under Queensland law and are provided in the Environmental Protection (Air) Policy 2019.
Dust management and reporting
Dust levels across resource operations are continuously monitored and must be kept to below criteria set under Queensland and Commonwealth law at sensitive receptors (e.g. residences). Dust emissions are managed through a combination of:
- Operational planning;
- Minimising disturbed areas;
- Undertaking progressive rehabilitation;
- Limiting road haul distances and traffic;
- Using enclosed conveyors;
- Veneering of train wagons (see section below);
- Load profiling of train wagons (see section below);
- Using water sprays on stockpiles and water carts on unpaved roads;
- Amending operations based on adverse forecast weather conditions; and
- Real-time monitoring.
Whilst the list is long, the resources sector is serious about minimising its impacts on communities and the environment and is always looking for ways to improve its performance, tackling each of the elements above.
In addition to the wide range of management measures implemented across operations, the resources sector reports emissions, including dust, annually to the National Pollutant Inventory (NPI). This reporting scheme is intended to provide transparency to the public and assist Government in identifying priorities for environmental policy and inform decision making.
It is important to note the NPI focuses on industry-related activities. Whilst other (e.g. diffuse) emissions are considered to a small extent, the NPI does not provide a complete representation of all sources of emissions across Australia or jurisdictions. As such, the data must be used with caution to avoid misrepresentation or misinterpretation.
QRC plays an important role in ensuring information released in the public domain, which represents activities undertaken by the resources sector, is factual and accurate. It is important for the community to understand what the numbers mean to them. In the case of the NPI, there is a public perception that the level of dust recorded by resource operations equals the equivalent level of impact on the community and the environment, however, this is not accurate. Under normal working conditions, dust generated during operations is largely retained within the proponent’s lease boundary and buffer lands and this is generally a requirement of operating approvals.
QRC is currently working with its member companies and Government to:
- Improve NPI reporting for the resources sector;
- Collate up-to-date data for other emission sources (beyond industry) to input into the NPI and deliver a complete representation of air emissions across jurisdictions; and
- Provide better information on NPI data for greater public understanding and interpretation.
Rail corridor coal dust management
The rail networks across Queensland offer an efficient means for the resources sector and others to transport products to ports for export trade.
To minimise coal dust emissions (lift-off) during transit, all coal mines in Queensland undertake veneering of loaded train wagons. This process involves spraying a biodegradable non-toxic agent onto the loaded coal surface at the time of loading, which then binds the top of the coal surface together forming a flexible, protective layer.
Details of coal dust management on the Western Metropolitan Rail System are provided below and can be found on Aurizon’s website along with measures for the Central Queensland Coal Network.
Coal dust management on the Western-Metropolitan Rail System
The Supply Chain that utilises the Western-Metropolitan Rail System (WMRS) is made up of two coal producers, a rail transport operator, a rail network manager and a coal export terminal operator. It is the smallest coal network in Australia.
Up to 10 million tonnes per annum of coal can be extracted from the Clarence-Moreton and Surat Basins in southern Queensland. Coal extracted is then hauled via the WMRS (approximately 650 kilometres return) for export through the Port of Brisbane. In addition to coal transport, the WMRS is used by passenger trains and freight trains, which haul grain and livestock.
In late 2012 and into 2013, communities along the WMRS raised concern with the Queensland Government that coal dust generated from uncovered rail wagons transporting product coal to the Port of Brisbane was a nuisance, particularly for neighboring residences. In response this concern, the Supply Chain, in collaboration with the Government, took action to understand the sources and impacts of coal dust through air quality monitoring and implement additional mitigation and management measures.
Scientific evidence is essential to establish an accurate picture of air quality and coal dust deposition levels along the WMRS. QRC, on behalf of the Supply Chain, commissioned the Queensland Department of Science, Information Technology and Innovation (DSITI) (now integrated as the Department of Environment and Science) to conduct independent baseline air quality monitoring along the WMRS between March and May 2013. Monitoring focused on acquiring data, including TSP, PM10, PM2.5, and dust deposition, to assess both health and nuisance impacts on the community and to identify the contribution of coal dust to total deposited dust levels. The Department’s analysis was later validated through a peer review process.
DSITI reported that rail transport emissions, including coal haulage, was compliant with air quality criteria for TSP, PM10, PM2.5, and dust deposition along the WMRS. Coal dust made up a minor fraction of total deposited dust levels with soil or rock dust being the major contributor.
Although the monitoring showed coal haulage met air quality criteria, the Supply Chain voluntarily adopted additional dust mitigation and management measures to further improve overall environmental performance and to address community concerns, including:
- Veneering, which involves the application of a biodegradable, non-toxic, binding agent onto the loaded wagon coal surface. The veneer forms a crust over the coal load and minimise coal dust lift-off in transit; and
- Load profiling, which involves shaping the exposed surface of coal above the sill of the wagon into a ‘garden bed’ profile, to minimise coal dust lift-off when the top of the loaded wagon in transit.
By the end of 2013, additional coal dust mitigation and management measures had been implemented across the Supply Chain consistent with commitments in the South West System Coal Dust Management Plan 2013 (see also South West Supply Chain Coal Dust Management Plan 2019). DSITI subsequently monitored air quality throughout 2014 and 2015 to obtain a long-term data trend, for TSP, PM10, PM2.5, and dust deposition, and to assess the ongoing effectiveness of the Supply Chain’s efforts.
The monitoring demonstrated that rail transport emissions, including coal haulage, continued to comply with air quality criteria for TSP, PM10, PM2.5, and dust deposition with coal dust making up a minor fraction of total deposited dust levels. The monitoring also highlighted that the implementation of additional mitigation measures had been highly effective in maintaining compliance and reducing the loss of coal dust from loaded rail wagons further during transit.
DSITI has since undertaken routine monitoring on the WMRS on behalf of the Supply Chain. The below figure shows the trend in total dust deposition levels since March 2013 to present. It also demonstrates that coal dust makes up a minor fraction of total deposited dust levels with the annual average coal dust deposition rate generally less than 1 mg/m2/day through to 2017 (after implementation of mitigation measures).
In 2018, the annual average coal dust deposition rate increased slightly to 2.2 mg/m2/day. However, this decreased in 2019 to 0.3 mg/m2/day, well below pre-veneering levels and the lowest annual average coal dust deposition rate measured across the rail corridor since the commencement of the study.
In 2018, the slight increase in the annual coal dust deposition rate was found to be due to coal deposition during drier periods of the year rather than being uniformly spread across all months and was therefore understood to be a result of meteorological conditions rather than losses from rail transport.
While dry conditions persisted in 2019, coal dust deposition decreased in 2019 compared to 2018, to the point where there was no coal dust deposited during the period August to December 2019. The most likely explanation for this is that with the extended period of dry conditions experienced in 2018 and into 2019, the majority of soil within the rail corridor containing coal from historical losses that was readily available for re-entrainment was effectively removed. This lack of historic coal dust in the rail corridor available for re-entrainment, coupled with Coal Dust Management Plan actions preventing any appreciable amounts of new coal being added to the rail corridor, resulted in the low coal dust deposition rates in 2019 despite the continuing dry conditions.
In 2020, the annual average coal dust deposition rate across the rail corridor as a whole in 2020 was almost non-detectable with less than 0.1 mg/m2/day, compared with 0.3 mg/m2/day in 2019.
Dust deposition changes with seasonal weather conditions.
The outlier in the September 2018 sample is largely due to local dust sources other than rail transport (including coal haulage). In validating, and removing the outlier, the deposited coal dust level is 3.5mg/m2/day. Refer to the Western-Metropolitan Rail System Coal Dust Monitoring Program Report 2018 for further details (pages 13, 17, 18, 22, 23).
Source: DSITI (2013, 2016, 2017) and Department of Environment and Science (2018, 2019, 2020)
Full details of the monitoring program and results are published in the links below.
To demonstrate ongoing compliance on the WMRS, monitoring remains in effect and will continue voluntarily for the foreseeable future. From 1 April 2021, the rail transport operator (QR) and network manager (Aurizon) will lead and take responsibility for this monitoring.
The current operation of the Supply Chain, including mitigation and management measures, is provided in the South West Supply Chain Coal Dust Management Plan 2019. For a summary of the Plan, refer to QRC’s Western-Metropolitan Rail System and Coal Haulage – In brief.
Queensland Government (2017) Particles, accessed November 2017, <https://www.qld.gov.au/environment/pollution/monitoring/air-pollution/particles>