Sustainability Report 2006/07Energy and greenhouse
Melbourne Water is a large user of energy, mostly for treating and pumping water and sewage. We meet our energy needs by buying electricity from the grid, using fuels such as natural gas and diesel, and generating renewable energy from our own activities.
We create renewable energy at our Eastern and Western sewage treatment plants by capturing and using biogas – a by-product of the sewage treatment process – to generate electricity. In the water supply network, we harness water flow and pressure to generate hydro-electricity.
Since 2000, we have made significant progress in reducing emissions and generating renewable energy.
We achieved our target of 45% renewable energy production and exceeded our target of a 38% reduction in greenhouse gas emissions. We reduced greenhouse gas emissions by more than 15% compared with 2005/06, and 53% compared with our baseline year of 2000/01.
Melbourne Water used 1.25 million gigajoules of energy this year, most of which came from imported electricity, biogas and generated electricity. Melbourne Water spends about $17 million a year on energy, our fourth largest expense after labour, IT and external expenses. Most of the energy is used for sewage transport and treatment.
Renewable energy production was lower than previous years due to lower biogas production at the Western Treatment Plant, ceasing generation at Thomson and Cardinia hydroelectric power stations due to drought effects, and the Eastern Green Energy Project at the Eastern Treatment Plant being delayed.
Renewable energy includes biogas used at the Eastern Treatment Plant and biogas for electricity with AGL at the Western Treatment Plant, plus the mini hydros. In order to achieve our renewable energy target, Renewable Energy Certificates were purchased and surrendered to the Office of the Renewable Energy Regulator.
Overall it takes more energy to treat one million litres of sewage than one million litres of water. This is unusual for a water authority and represents the advantages of having protected catchments that provide good quality water needing minimal treatment, and a gravity fed system.
The challenge for Melbourne Water is that energy consumption is predicted to rise in the coming years due to drought recovery, tertiary treatment at the Eastern Treatment Plant, energy required for pumping in the Sugarloaf Pipeline Project and the Tarago Treatment Plant. Work is currently underway on the Greenhouse Emissions Reduction and Renewable Energy Use Strategy, due for completion in 2007/08.
Since 2000/01, significant reductions in our greenhouse gas emissions were achieved from the following:
Actions |
Result (tonnes Co2e per year) |
|---|---|
| Ceasing land application of sewage at the Western Treatment Plant | 131,000 |
| Collecting biogas to generate electricity at the Western Treatment Plant | 84,000 |
| Upgrading secondary aeration tanks at the Eastern Treatment Plant | 7,000 |
| Tree planting along waterways (offset) | 2,000 |
| Incorporating hybrid cars into the operating fleet | 147 |
| Initiatives identified through energy efficiency studies | 115 |
| Total | 224,262 |
Harnessing the power of biogas
This year marks the first full year of operation for the enlarged biogas power generation facilities at the Western Treatment Plant.
We reduce greenhouse gas emissions and odour by capturing increasing quantities of biogas collected from covered sewage treatment lagoons.
A power generation facility run by AGL, in partnership with Melbourne Water, generates electricity using biogas captured in the treatment process. We use this electricity to help meet our energy needs.
The biogas generators are expected to produce about 70% of energy needs at the Western Treatment Plant, and generate more than 50 gigawatt hours a year of renewable energy.
However, this year there was a reduction in the amount of biogas generated by the covered lagoons and a fire which destroyed an AGL generator. This resulted in a 25% reduction in electricity generation.
Eastern Green Energy Project
Our Eastern Treatment Plant is set to begin reducing greenhouse gas emissions and creating renewable energy with the successful completion of the $46 million Eastern Green Energy Project.
This innovative project uses biogas produced during the sewage treatment process to fuel electricity generators, and reduces greenhouse gas emissions by reducing imports of grid electricity and diesel fuel oil. The electricity generated is used to help power treatment processes.
The project is expected to produce about 50% of the plant’s energy needs and reduce electricity imported from the grid by about 28,000 megawatt hours per year (which is equivalent to the annual electricity consumption of about 3000 houses). It will also reduce greenhouse gas emissions by about 32,000 tonnes a year, and help us achieve 100% renewable energy use by 2018.
Our 2018 targets
We have set ambitious targets for achieving zero net greenhouse gas emissions and producing or exporting enough energy from renewable sources equivalent to our energy needs by 2018.
We aim to meet our 2018 target of zero net greenhouse gas emissions by:
- Avoiding energy use
- Improving efficiency of operations
- Using waste as an energy resource
- Using renewable energy sources
- Purchasing offsets, if necessary, as a last resort
- Sequestering carbon - removal of carbon dioxide from the atmosphere by the growing of organic matter (usually trees) and ensuring the carbon is immobilised for a signifi cant period of time (usually more than 100 years).
Operational efficiency
Significant energy savings can be achieved by optimising the way we operate our infrastructure.
We have reviewed energy consumption at our largest pumping stations – Hoppers Crossing, Brooklyn, Yering Gorge and inflow (influent) pumps and aeration blowers at the Eastern Treatment Plant – which combined are responsible for more than 60% of our electricity use.
Efficiency reviews helped identify equipment needing refurbishment, and further analysis has identified each site’s optimal combination of pumps. This information will be used to develop the most energy-efficient operational procedures.
We have registered for the Commonwealth Energy Opportunities Scheme, which requires businesses using more than 0.5 petajoules of energy a year to identify energy efficiency opportunities and report on assessment outcomes.
Mini hydro-electricity plants
Detailed planning continues on six new mini hydro-electricity plants on the water supply network, to supplement the existing ones at Thomson Reservoir and in the Silvan-Cardinia pipeline.
The new plants provide an alternative to existing pressure relief valves in the water supply system, converting the pressure of water flowing into renewable energy via power generators. The energy will be exported to the Victorian electricity grid.
The first plant, at Preston, has moved into the design and construction phase, and is expected to become operational in mid-2008.
The six mini-hydro plants will generate a total of 40,000 megawatt hours, equivalent to the amount of energy required to power 5000 homes.
Sharing our expertise
Through our development of renewable energy sources and ways to minimise greenhouse gas emissions, we have developed significant expertise, which we share with the wider water industry.
We presented an energy and greenhouse gas workshop on our management of energy and greenhouse gas emissions to the Victorian water industry, helped develop the automated Greencount emissions calculation assessment tool in conjunction with the Water Services Association of Australia, and worked with the Australian Greenhouse Office to clarify water industry issues.
We also maintained our membership of the Commonwealth Greenhouse Challenge Plus. This program enables Australian companies to form working partnerships with the Federal Government to improve energy efficiency and reduce greenhouse gas emissions.
