Air Emissions
Normal operations on the Prelude facility generates atmospheric emissions, which include greenhouse gases. Shell has implemented key mitigation strategies to manage the potential impacts of these emissions on the surrounding environment.
Atmospheric emissions and Greenhouse Gas emissions
The operations of the Prelude FLNG facility produces atmospheric emissions and greenhouse gas emissions from:
- fuel combustion for power generation and compression
- flaring for safety purposes
- disposal (venting) of reservoir CO2
- fugitive emissions and general leaks
For a detailed summary, select your potential impact of interest:
Atmospheric emissions
Atmospheric emissions
As the facility is located 200km from the Western Australian coast, only the immediate physical environment (air quality and visual amenity) has the potential to be impacted by atmospheric emissions.
Impacts on the physical environment will be the result of:
- planned emissions of atmospheric pollutants to the facility’s airshed under routine and non-routine (planned and emergency) operating conditions
- routine and non-routine flaring resulting in smoky flare
The facility’s airshed and impacts of the combined emission sources have been examined in an air quality modelling study. The study modelled emissions under three different scenarios – normal operations, exceptional operations and worst reasonable exceptional operations. Emissions from the nearby Ichthys petroleum operations, were also modelled to understand the cumulative effects of atmospheric emissions.
These modelled emissions were then compared to current and future air quality standards:
The Australian Ambient Air Quality Standards (AAQS) (National Environment Protection Council 1998)
New draft ambient air quality standards for NO2, SO2 and PM2.5 listed in the proposed NEPM Air Quality Measure (National Environment Protection Council 2019)
Results for all three scenarios predict ground-level concentrations of pollutants at the nearest receptor (i.e. Browse Island) to be well below the assessed air quality standards.
Apart from the aesthetic impact associated with a slightly smoky flare, there would be no material environmental impacts to local and regional airshed quality.
Key controls and mitigations
Representative boiler stack samples carried out at least once.
A surveillance program is in place for the boilers and power generation units to ensure that they are operating within the design operating envelope.
Use only low sulphur fuel oil/ diesel for FLNG and marine support vessels.
Specified vessels are required to have the valid atmospheric emissions management documentation as required by class.
Collect and estimate total air emissions to the National Pollutant Inventory regulator.
Undertake targeted topside fugitive emissions monitoring on an annual basis.
Greenhouse Gas emissions
Greenhouse Gas emissions
Anthropogenic emissions of greenhouse gas to the earth’s atmosphere have been recognised by reputable scientific bodies, international organisations and governments around the world as the single most important factor leading to accelerated climate change and global warming. Trends and effects have been closely monitored since the second half of the last century. Environmental impacts from global warming and climate change act on a global scale.
The greenhouse gas inventory for the highest production throughput year, during the first five-year period, indicates 97% of all scope 1 greenhouse gas emissions to be contributable to fuel combustion and reservoir CO2 venting. Flaring and fugitive emissions constitute less than 3% of the total. These results indicate that the greenhouse gas emissions associated with Prelude operations will depend primarily on the CO2 content of the reservoir.
Prelude has been designed to operate in a way which reduces greenhouse gas emissions, including:
- Locating Prelude in close proximity to the gas field, eliminating the need for long pipelines to shore.
- Integrating product offloading facilities into Prelude’s design, avoiding additional energy use for gas compression which is needed to export gas to an onshore terminal.
- Using Shell’s proprietary double mixed refrigerant process, ensuring efficient use of power and less fuel gas demand.
- Using colder seawater from a depth of 150m, rather than surface water, reducing the need to cool the water and leading to greater LNG production using the same energy inputs.
Key controls and mitigations
- Implement GHG minimisation as per the Prelude Operations Playbook during planned plant shutdowns and start-ups.
- Conduct an annual forecast of future greenhouse gas emissions from Prelude FLNG.
- Collate and estimate total greenhouse gas emissions from Prelude FLNG and report to the Clean Energy Regulator.
- Undertake targeted topside fugitive emissions monitoring on an annual basis.
- Commence monitoring plant energy performance using Carbon and Energy Management Information System within 18 months of completion of all relevant performance tests for specified plant equipment.
