To decarbonise, we need to understand where our carbon comes from and how we can reduce it.

AECOM has been working closely with Waka Kotahi NZ Transport Agency to understand and reduce emissions from the construction, operation, and maintenance of land transport infrastructure. A vital component of this ongoing work has been calculating emissions related to recent Waka Kotahi projects. We have been identifying New Zealand’s largest infrastructure emissions sources, creating baselines of emissions based on international studies, and developing an emissions estimation tool known as PEET (Project Emissions Estimation Tool) for future projects.

Taking climate change measures in infrastructure

New Zealand’s government implemented a Climate Implications Policy Assessment (CIPA) requirement in 2019. All major infrastructure proposals initiated by central government agencies that go to Cabinet for funding, must undertake a CIPA. This requirement enables New Zealand to measure, monitor and report on Cabinet decisions that impact the country’s greenhouse gas emissions. Through the work undertaken for the NZ Upgrade Programme CIPA assessments, we developed PEET in collaboration with Waka Kotahi as a standardised tool that can be applied to various projects.

Establishing a project emissions estimation tool

Emissions are typically determined during the design phase of a project, which is too late, as many key design elements have already been decided, making it difficult to change the design to reduce emissions. PEET is a whole-of-life greenhouse gas (GHG) emissions tool that allows users to embed an understanding of the potential impacts of infrastructure-related emissions early in the business case/pre-design phase and consider alternative options when making investment and design decisions. The tool has been split into three user modes to allow for variable levels of data detail when running the tool. PEET captures emissions through construction, operations and maintenance and estimates emissions associated with vehicle use (enabled/avoided emissions) by integrating Waka Kotahi’s Vehicle Emissions Prediction Model.

The tool has been further developed in collaboration with Auckland Transport and KiwiRail to include elements for local authorities and rail projects. An emissions reduction analysis is built into PEET so that users can understand the effect of using currently available emission-reducing options and materials like low-cement concrete, high-recycled content steel, recycled asphalt pavement, and recycled crushed concrete. By ensuring that emissions are easily accounted for in the business case or pre-design phase, users can identify hot spots and reduce carbon emissions which could impact hundreds of thousands of tonnes of carbon dioxide.

Achieving emission reduction goals

PEET enables government agencies, local authorities and infrastructure providers to achieve the emissions reduction targets outlined in the New Zealand Emissions Reduction Plan released in 2022. By quantifying and assessing possible emissions, PEET empowers users to realise the effects of material choices and how they can lower embodied carbon or even reduce/remove specific design packages from projects.

Auckland Transport engaged AECOM to complete a GHG Baseline and Emission Reduction Assessment of the Regional Land Transport Plan (RLTP) using PEET. The total embodied emissions of the RLTP were estimated at 1,532,691 tCO2e, and a reduction of 346,799 tCO2e (23%) was modelled using low-carbon material options. This analysis was used to inform Auckland Transport’s embodied GHG emissions target of 50% by 2031. Adopting the embodied emissions target establishes Auckland Transport as a leader in this area and complements existing targets that address other sources of transport emissions.