TOWARDS THE REGULATION OF NON-ROAD DIESEL EMISSIONS IN AUSTRALIA

whereas road vehicles are operated under highly transient conditions.

 The spatial and temporal patterns of activity for NRDE are less well understood and more difficult to estimate (Cravigan & Smit 2015).

Air pollutants from diesel engines can cause harm to human health and the environment (e.g. Weitekamp et al. 2020), and regulations for NRDE emissions have been in force in the United States (US) and the European Union (EU) since the mid-1990s. The regulations have evolved to cover a wider range of engine power and to increase the stringency of the emission limits. The first Australian emission standards for diesel road vehicles became effective in 1995, but there are still no corresponding Australian standards for NRDEs.

NRDEs are a significant – but poorly characterised –contributor to air pollution in Australia. NRDEs consume a volume of diesel that is comparable to that of road vehicles, despite there being far fewer engines in use, and they also have higher emissions per litre of diesel consumed due to the lack of regulation.

This ‘whole of Australia’ impact pathway analysis for NRDEs defined the stock and spatial distributions of emissions, air pollutant concentrations and health outcomes in a business-as-usual (BAU) scenario and three specific emission management scenarios.

2. Scope of analysis

2.1. Equipment

The analysis included 27 different types of equipment covering various applications (Table 1). The definitions were taken from Kinrade et al. (2020), and reflected the emission regulations in the US and EU. In the US, NRDEs include engines installed in (i) self-propelled equipment, (ii) equipment that is propelled while performing its function, or (iii) equipment that is stationary but transportable. The EU defines a wider category of non-road mobile machinery, which covers ‘any mobile machine, transportable industrial equipment or vehicle with or without bodywork, not intended for the use of passenger or goods transport on the road, in which an internal combustion engine is installed’. Broadly in line with the US regulatory approach, the following engines and equipment were excluded from the analysis:

 Diesel locomotives.

 International and interstate commercial marine engines (>130 kW)*.

 Aircraft engines.

 Underground mining equipment.

 Engines used in the defence sector (due to the sensitivity of the associated information).

*Marine engines <130 kW were included as ‘recreational boats’.

2.2. Emission standards

The Australian NRDE stock was also defined in terms of emission standards. Again in line with the US regulations, these were specified as tiers with increasingly stringent emission limits. Unregulated engines were assigned to Tier 0, and regulated engines were assigned to Tier 1, Tier 2, Tier 3 or Tier 4. The Tier 4 standards had an initial interim stage (Tier 4i), and a second, more stringent final stage (Tier 4f).

2.3. Scenarios

Four scenarios were considered in the analysis:

 BAU: business as usual. Expected evolution of the NRDE stock in the absence of emission standards or other management approaches.

 MS1: industry agreement (non-regulatory). Industry would agree to meet sales targets for new NRDE which align with current US emission standards (Tier 4f) (implementation year 2026).

 MS2: phased standards (regulatory). Interim emission standards (Tier 3) would be introduced as soon as practicable (2026), with a subsequent transition to Tier 4f (2030).

 MS3: best practice standards. Tier 4f emission standards would be introduced as soon as practicable (2026).

2.4. Timeframe

Detailed data on NRDE stock and emissions were determined for three datum years: 2018, 2028 and 2043. The data for the 2018 base year defined the situation at the start of the analysis period. The data for 2043 defined the situation 25 years later, and 2028 provided an intermediate point to account for non-linearity in the time series. However, many engines purchased near the end of the 25-year period would remain in service for years afterwards, and this would have consequences for health. Moreover, the health benefits of a reduction in NRDE emissions would be gradually realised over time for the exposed population by extending life