Page 35 - EER-1-1

Explora: Environment
and Resource WTW emissions of road, rail, sea, and air transport

1. Introduction taken into account in the emission simulations.

Australia has committed to reducing its greenhouse gas The following questions were addressed by this analysis:
(GHG) emissions by 43% below 2005 levels by 2030 and • Are there any Australia-specific models and data that
achieving net-zero emissions by 2050. Reducing emissions can be used to quantify the GHG emission intensity
from the transport sector is a crucial, but challenging of different transport modes (in particular sea and air
element of the net-zero strategy. In the year 2018 – 2019, transport)?
domestic transport was responsible for 100 Mt of carbon • How can the impacts of variability and uncertainty in
dioxide equivalents (CO -e), or 18% of gross national emission estimates be taken into account?
2
emissions. Within the sector, the largest source by far • What are the potential emission benefits of transferring
was road transport (85%), with itself dominated by cars passengers and freight from high-intensity modes to
and light commercial vehicles with internal combustion low-intensity modes?
engines (ICEVs). Civil aviation (8%), railways (4%),
and marine navigation (2%) were minor contributors to 2. Methods
domestic transport emissions. 1 2.1. Characterization of GHG emissions
In the same year, Australia’s domestic passenger travel For consistency with Part I of the study, the analysis used
was 443 billion passenger-km (pkm). The majority of this a “fuel/energy lifecycle” approach to characterize GHG
travel was by road (79%, including a small contribution emissions. This approach is also referred to conceptually as
from ferries), with 4% by rail and 17% by air. Domestic “well-to-wheel” for road and rail transport, “well-to-wake”
freight activity was 785 billion tonne-km (tkm). In this for sea or air transport, and sometimes “tank-to-propeller”
case, the majority was by road (28%) and rail (56%), for sea transport or “well-to-wing” for air transport. For
with sea (coastal shipping, 15%) making up most of the each mode, the full cycle is abbreviated here as well-to-
remainder. Freight transport by air was less than 0.05% of wheel/wake (WTW), and the calculation of emissions
the total. 2 involves two steps. The first step calculates direct emissions
Shifting activity between transport modes – and from vehicles on the move and is referred to as “tank-to-
specifically from modes with a high emission intensity to wheel” (TTW) for road and rail transport, “tank-to-wake”
modes with a low emission intensity – will have to be an for sea transport, and “tank-to-wing” for air transport,
important consideration in the net-zero strategy. Part I abbreviated in each case as TTW. The second step calculates
of this study provided additional context on mode-shift indirect emissions associated with fuel extraction, energy
3
approaches, but noted that there have been few studies production (fossil fuels, electricity, and H ), and distribution
2
using Australian data. Part I, therefore, considered the and is referred to as “well-to-tank” (WTT), which applies
potential of mode shift in land transport – specifically from to all modes. Although the production, maintenance, and
road to rail – to reduce GHG emissions, with reference disposal of vehicles and infrastructure were not taken into
to real-world Australian scenarios and using local data account in this analysis, the WTW analysis is expected to
where possible. The scenarios involved the movement have captured the bulk of the total GHG emissions over the
of passengers and freight between two Australian state considered time frame, 65,66 which is particularly the case for
capital cities: Brisbane and Melbourne. The analysis used high-mileage transport modes such as ships and aircraft
a probabilistic approach which provided insight into the with long operational lifetimes.
uncertainty and robustness of the modeling approaches. The main outputs of the analysis were the WTW
This paper describes Part II of the study, which emission intensities (ε) of CO -e for freight transport
2
expanded the mode shift analysis from Part I to include sea by sea, and passenger and freight transport by air, with
and air transport. For consistency, the methodology from emissions normalized for passengers, payload, and distance
Part I was mostly retained, although sea and air transport (i.e., g/pkm or g/tkm). Passenger transport by sea could also
have certain characteristics, as well as more limitations on have been assessed in principle, but it was not considered to
data availability, which required changes to the simulation be a realistic alternative to the other modes for the Brisbane
approach. To elaborate on the first point, sea and air – Melbourne route and was therefore excluded. Three years
transport occur in moving media, and are subject to were modeled: a 2019 base year, and the target years for
currents and winds, which affect energy use and emissions. GHG reduction in Australia of 2030 and 2050.
When comparing an aircraft with a car, truck, train, or
ship, the mass of the fuel represents a larger proportion of 2.2. Transport routes
the total vehicle mass. Therefore, for an aircraft, the total Sea and air transport routes between Brisbane and
mass changes significantly during a journey, which was Melbourne were defined for the analysis, and these are

Volume 1 Issue 1 (2024) 2 doi: 10.36922/eer.3471