As an organization, PUB’s emissions in 2020 are approximately 460 kt CO2e as reported in PUB's Sustainability Report 2020/2021. To achieve its net-zero goal, PUB will need to implement new technologies and solutions to address emissions associated with its
water facilities. PUB has built a robust and diversified supply of water, including NEWater facilities that recycle used water and desalination facilities that convert seawater to drinking water (see FIGURE 1).
However, many of these processes are inherently energy-intensive and PUB’s emissions are projected to increase with population rise and economic growth in the coming decades. By mid-century, emissions could double to 1 MtCO2e.
PUB is already working to reduce its carbon footprint by replacing carbon-emitting energy sources with solar PV deployed on facility rooftops and at reservoirs, and reducing carbon emissions through energy efficiency, lowering desalination energy and conservation. These efforts are expected to abate approximately 600 kt CO2e/year of emissions by mid-century.
While current efforts can reduce PUB’s future carbon footprint substantially, PUB is seeking solutions to remove an additional 400 kt CO2e/year associated with its facilities that will require solutions such as carbon capture, utilization and storage (CCUS) and carbon removal (see
FIGURE 1 and TABLE 1).
PUB Water Loop
Projected Emissions from PUB
PUB’s projected Scope 1 emissions that will require new solutions (200 kt CO2e/year) are associated with its four water reclamation facilities and come from two sources:
● Approximately 100 kt CO2e/year from anaerobic digester processes that result in an emissions stream containing approximately 35% carbon dioxide; 62% biomethane; and 3% mixed gases that are primarily hydrogen sulfide and nitrous oxide.
● Approximately 100 kt CO2e/year of mostly nitrous oxide emissions from nitrification/denitrification that happens in the aerobic wastewater treatment processes.
FIGURE 2 illustrates a typical water reclamation process and the sources of Scope 1 emissions.
Typical Water Reclamation Process and Scope 1 Emissions
The remaining Scope 2 emissions (200 kt CO2e/year) are due to the electricity used to power PUB’s facilities, for example water treatment plants, desalination plants, NEWater Factories and used water treatment plants.