Landfills: climate change adaptation case study

Preventing and managing odour generation exacerbated by extreme rainfall at landfills and waste management facilities.

This future scenario outlines possible climate impacts, risks, adaptation measures and ongoing management measures at a hypothetical site in NSW.

Scenario

A privately owned landfill facility in Mid-North Coast New South Wales (NSW) has recently experienced periods of heavy rainfall. Following this period, the landfill experienced increased odour generation from the landfill cells and received multiple odour complaints from nearby residents.

The Facility owner recognised that the odour incidents associated with extreme rainfall were occurring more frequently. They undertook preliminary investigations to better understand the Facility’s exposure to climate risk. The investigation indicated that with each degree of global warming, the frequency of intense rainfall events is projected to almost double¹. The assessment also found that there will be an approximate 7% rise in rainfall intensity with each degree of warming that is realised which would result in the system being even more vulnerable to extreme rainfall events². By 2050, the region is likely to experience a 66 mm increase in rainfall depths during a 1 in 100-year, 24-hour storm duration under a higher emissions pathway³.

Climate impacts

After the heavy rainfall event, the Facility owner identified that the off-site odour impacts and resulting odour complaints, were caused by excess landfill gas generation. There were 3 modes by which the excess gas was generated:

• rainwater infiltration through an area where the landfill cap was compromised, increasing the rate of waste decomposition
• active landfills being saturated though exposed tipping face, expediting the decomposition of waste
• the landfill gas and leachate capture and treatment systems going offline during the rainfall event.

The Facility owner realised that while the landfill cells (both active and inactive) were impacted in the rainfall event, there may be other components of the Facility that could also be impacted by climate change and could result in adverse odour impacts.

Further, the Facility owner noted that the existing systems such as leachate ponds, stormwater networks, and landfill gas capture systems were designed using historical rainfall data and may not be able to manage current and projected rainfall. Without the adaptive capacity to manage increasing rainfall, unmanaged odour generation could become more commonplace.

Assessing climate risk

To understand the climate change impacts on the Facility, and to prioritise climate risk management, the Facility undertook a system wide climate change risk assessment using climate projection data for rainfall, temperature, fire and extreme storms. While several climate hazards and potential climate related impacts related to the Facility were identified, this scenario focusses on increased volume and intensity of rainfall, resulting in exacerbation of odour impacts.

The assessment was undertaken across the remaining asset life of the Facility using projected climate data for a medium and high emissions climate scenario. The system was found to be at higher risk of excessive odour generation during extreme rainfall events.

Identifying Adaptation Measures

With the key climate risks identified, the Facility owner and key stakeholders such as the landfill operator collaborated to identify potential adaptation measures that could be implemented to reduce these climate risks and associated impacts. The adaptation measures targeted different infrastructure components and vulnerabilities of the system, with each having different levels of feasibility and effectiveness in addressing climate change induced environmental impacts.

The Facility owner identified a number of adaptation options that could be implemented at its operational and closed landfill cells to reduce the likelihood of odour incidents during extreme rainfall events. These included:

• Developing and/or updating site-specific management plans, manuals and operational procedures including maintenance manuals, vegetation management plans (for landfill caps), aftercare management plans (for closed landfill cells and those approaching closure), and asset management plans to account for extreme rainfall incidents. The Facility owner recognises this as a low-cost measure often only requiring an additional ‘climate’ consideration to an already existing system or plan. These plans must clearly specify roles and responsibilities to ensure accountability of implementation and maintenance of these documents. As the climate changes, the review and refinement of these administrative controls may need to occur at increasing frequency.
• Prioritisation and investment in regular preventative maintenance checks of landfill cells to ensure they are not compromised during future rainfall events. These checks would be of the lining, capping, and temporary cover to reduce the likelihood of rainwater infiltration. Routine checks of the gas and leachate extraction systems should also occur to ensure they operate at maximum efficiency when required. Over time the frequency of maintenance checks may increase and should be documented in site plans, manuals, guidelines, and/or procedures.
• Embedding redundancy in the system to ensure that if part of the leachate and landfill gas management system goes offline during a peak rainfall event, or if the extraction/treatment capacity is nearing its limit, the facility can remain operational and prevent generation and release of excess odour. This could include having backup power supply to maintain operation of critical processes or having alternative pipelines/valves to redirect flows as required.
• New landfill cells should be designed in accordance with relevant industry and regulatory guidelines including the Environmental Guidelines: Solid Waste Landfills (or latest revision available) including adequate slope to enable drainage of stormwater and prevent pooling in any areas of temporary cover or final capped landfill. These designs should take into account appropriate climate change scenarios so that infrastructure can capture and divert rainwater from the waste and ultimately preventing it from creating conditions that could result in excess odour generation.
• For existing landfills, the landfill cap design, leachate management design, and surface water management systems should be assessed against relevant standards and guidelines, such as the Australian Rainfall and Runoff Guidelines (ARR) 2019 v4.2, and the Environmental Guidelines: Solid Waste Landfills (or latest revision available), to understand the existing capacity of the existing system to minimise leachate and odour generation and abide by compliance requirements.
• For existing landfills, the feasibility of retrofitting landfill gas capture and treatment infrastructure could be investigated to better manage odour issues.
• Preventative controls should be undertaken, such as implementing daily covering to the tipping face of landfills at the end of each operational day to minimise exposure to rainfall. As per EPA Solid Waste Landfills Guide, Virgin Excavated Natural Material (VENM) should be used where possible to provide a protective layer and minimise the volume of wet waste and odour generation. Minimising the area of the tipping face also reduces the exposure of the waste to extreme rainfall.

Ongoing management of climate impacts

The above adaptation measures focus on an increased volume and intensity of rainfall resulting in odour generation - which represents a sample of the long list of potential actions the Facility owner identified which will be included in a climate adaptation plan for the Facility.

An adaptation pathway will then be developed to ensure that adaptation measures are prioritised and implemented based on key trigger points. Key trigger points will be identified based on when the climate change impacts may eventuate in environmental risk, where there is opportunity to improve environmental performance, as well as taking into consideration the age, condition and criticality of the infrastructure and likely timelines for infrastructure upgrades. The adaptation pathway will enable the Facility to address the high-risk, time critical climate change impacts now while remaining open to future adjustments as the climate evolves.

Climate risk management is an iterative process and should be reviewed periodically to ensure the risk assessment and adaptation pathway remain effective and appropriate into the future. By planning ahead and building adaptability into administrative controls and infrastructure, the landfill and waste management industry can reduce its vulnerability, safeguard its facilities, and protect