We want to reduce our operational greenhouse gas emissions related to our wholesale businesses by 34% compared to 1990 by 2020.
We aim to reduce dependency on energy from the grid by improving energy efficiency and increasing our self-generation percentage (mainly from our sludge treatment), reducing our net energy import from the grid across wholesale wastewater services by approximately 33 per cent by 2020.
We want to increase our power generation of renewable energy to 405 Gwh.
We also want to reduce dependency on the energy grid for wholesale water services by improving energy efficiency and reducing our net energy import from the grid by 8.7 per cent by 2020.
Thermal Hydrolysis Process
We are improving the effectiveness of some of our anaerobic digesters by fitting an additional pre-treatment process called thermal hydrolysis (THP).
This effectively involves pressure-cooking sludge at 160 degrees Celsius for about 40 minutes. During this time the sludge must, for a few seconds, be heated to 800 degrees Celsius to destroy harmful dioxins.
Sludge put through this process produces up to 50 per cent more biogas during anaerobic digestion, breaking down far quicker than ordinary sludge.
The extra biogas produced can be used as a fuel to generate renewable electricity using Combined Heat and Power units.
It is an ongoing challenge to beneficially recycle treated sewage sludge to agricultural land as a form of natural fertilizer.
THP has an additional benefit that less sludge is produced via the anaerobic digestion process, meaning less sludge to manage. This also reduces vehicles movements which helps to manage our carbon emissions.