The Northern Territory Environment Protection Authority (NT EPA) regulates air emissions, including air toxics, from the Santos Darwin LNG (DLNG) facility in Darwin Harbour to ensure those emissions do not cause unacceptable environmental and human health impacts.
The NT EPA is aware of fugitive methane leaks from the Santos LNG tank. Fugitive emissions occur at all LNG facilities however, the cause of the emissions from the DLNG tank is unique to this facility. Santos monitors fugitive emissions annually and average emission rates are estimated as 80 ± 5 kg/hr (~20.8 kt CO2-e gross per year). The estimated emissions from the LNG tank leak are approximately equivalent to 1% of Santos’s facility’s total annual greenhouse gas emissions and approximately 0.1% of the NT’s emissions.
It is important to note that methane is not classified as a toxicant. While methane is a flammable gas and can cause asphyxiation at very high concentrations, sampling by Santos has confirmed that fugitive emissions from the tank are significantly below hazardous levels.
The NT EPA did not report the leak to the public because at these levels they do not pose any risk of explosion and negligible risk to human health or the environment. The NT EPA continued to regulate the facility including annual inspections and requiring submission of all independent expert engineering reports and data. The NT EPA regulates Santos under an NT EPA licence distinct from the Clean Energy Regulator’s (CER) framework for regulating greenhouse gas emissions.
According to Santos, the leak at the DLNG tank originated during its initial commissioning in 2006 due to a design fault. This was reported to the NT EPA and NT WorkSafe at the time, and an independent investigation subsequently cleared the tank for continued use. The NT EPA was notified of the fugitive emissions from the LNG tank in May 2020. More recently, as part of the DLNG life extension project, a reassessment by independent engineering consultants (2023) confirmed that the tank remains structurally sound and safe for operation until at least 2050.
The leaking gas is composed of 99.3% methane, with trace amounts of other non-toxic gases and represents 1.04% of the facility’s total annual greenhouse gas emissions. While methane is not a toxic substance, it is a greenhouse gas of regulatory concern. The Australian Government, through the CER, is responsible for regulating greenhouse gas emissions, and the NT EPA has notified the CER as the appropriate authority.
Fugitive emissions are included in reporting to the CER and are subject to the Safeguard Mechanism. Under the mechanism, Santos is obliged to reduce its emissions over time or purchase Australian Carbon Credit Units (ACCU) to offset emissions.
The Environment Protection Licence (EPL217) issued for the hydrocarbon facility allows emissions to air and water from authorised discharge and emission points. The licence (EPL217-04) is due for renewal on 18 September 2025. The regulator is in the process of assessing the licence application and will apply the ALARP (as low as reasonably practicable) principle. This principle includes a consideration of cost in reducing risks to as low as reasonably practicable. The current licence will continue to be in operation until a new licence is issued.
Ensuring licence conditions relating to air emissions and monitoring are consistent across the industry and adhere to world’s best, or leading edge, practice will provide public confidence that the regulator is maintaining appropriate oversight.
While the NT EPA will continue to monitor the situation, the facility’s fugitive methane emissions are adequately regulated through the Safeguard Mechanism and any duplicative regulation by the NT EPA of the same emissions makes no sense whatsoever.