Sustainability Report 2006/07Greenhouse gas emissions
Melbourne Water is among the top 15 energy users in Victoria and among the top 300 energy users in Australia, and produced 284,500 tonnes of greenhouse gas emissions (CO2 equivalent) this year.
We use energy primarily for treating and pumping sewage and water, and 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.
In 2007/08, Melbourne Water used 1.368 million gigajoules of energy compared with 1.248 million gigajoules the previous year – an increase of 9.6%.
The increase in energy consumption is due to the additional pumping requirements associated with pumping water from the Yarra River at Yering Gorge and treating water at the Winneke water treatment plant to ensure security of water supply.
Melbourne Water spent $15.7 million this year on energy (3.9% of operating expenditure) compared with $16.2 million (5% of operating expenditure) last year. We have made significant progress in reducing greenhouse gas emissions and generating renewable energy since 2000.
At our Eastern and Western sewage treatment plants we create renewable energy 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.
This year we exceeded our target of a 40% reduction in greenhouse gas emissions. We reduced greenhouse gas emissions by 50.4% compared with our baseline year of 2000/01. However, we failed to meet our target of 50% of renewable energy used or produced, with 41.3% of our energy needs being supplied from renewable sources.
Our ability to produce renewable energy was affected mainly by drought impacts restricting hydro-electricity generation at the Thomson and Cardinia power stations.
Melbourne Water decided not to buy Renewable Energy Certificates to achieve the renewable energy target because we had already exceeded the more critical greenhouse gas emission reduction target and because of financial considerations.
Energy consumption is expected 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 water treatment plant.
To help address these issues and meet our long-term target of 100% renewable energy by 2018, we began developing a greenhouse emissions reduction and renewable energy use strategy. The strategy is due to be completed in April 2009.
Actions to reduce emissions
Since 2000/01, significant reductions in our greenhouse gas emissions were achieved from the following:
Renewable power from biogas
Melbourne Water uses biogas produced during the sewage treatment process to fuel electricity generators, reducing greenhouse gas emissions by importing less grid electricity and diesel fuel oil. The electricity generated is used to help power treatment processes.
This year we experienced minor technical problems affecting biogas generation facilities at the Eastern and Western treatment plants.
Despite these issues, we maintained our production of renewable energy from biogas, producing a total of 565 gigajoules.
At the Western Treatment Plant, a power generation facility run by AGL in partnership with Melbourne Water generates electricity using biogas captured in the treatment process.
The biogas generators produce about 70% of energy needs at the Western Treatment Plant, generating more than 50 gigawatt hours a year of renewable energy.
Lower sewage flows associated with the drought reduced the amount of biogas generated by the covered lagoons, and replacement of an AGL generator destroyed by fire in December 2006 was not brought online until September 2007.
Our Eastern Treatment Plant completed the Eastern Green Energy Project. The project is expected to produce about 50% of the plant’s energy needs, reducing electricity imported from the grid by about 28 gigawatt hours per year, and cut greenhouse gas emissions by about 32,000 tonnes a year.
However, the project delivered lower than expected electricity generation this year due to gas compressor reliability issues, power station engine breakdowns, and operational interruptions required as part of the commissioning process.
Renewable power from hydro
Hydro-electricity is playing an increasingly important role in providing renewable energy for Melbourne Water, with six new mini-hydro systems expected to be operational by 2009.
However, power generation from existing hydro plants at the Thomson Reservoir and the Silvan-Cardinia pipeline was well down this year due to low reservoir levels associated with the prolonged drought resulting in failure to meet our renewable energy target.
The Thomson hydro plant was online for only two months, producing just 946 megawatt hours (MWh) of electricity compared with about 15,000 MWh in a normal year. The Cardinia hydro operated all year, but at reduced levels, producing 11,350 MWh compared with about 14,000 MWh in a normal year.
Investigating new sources of green energy
Melbourne Water has set ambitious targets for 2018 of zero net greenhouse gas emissions and 100% renewable energy used or exported. Sourcing renewable energy substitutes for grid-supplied electricity is the key to achieving these targets.
A consultant’s report identified limited options to increase the amount of renewable energy produced through our own resources. These options included:
- Producing biogas from crops and plants (biomass) grown onsite or imported from offsite
- Increased production of biogas at sewage treatment plants through process improvements
- Constructing additional mini hydro-electric power stations
- Wind power, if suitable sites could be located.
Melbourne Water is working with several companies to develop sources of biomass for conversion to fuels and biogas for use in existing biogas electricity generators. A promising source of biomass is the nutrient-rich water at sewage treatment plants, which can be used to grow algae, and a pilot project is expected to be established at the Western Treatment Plant in 2008/09.
We also investigated the feasibility of installing wind turbines, and during 2008/09 we will conduct more detailed wind resource studies as a first step in confirming the suitability of using wind turbines at promising locations.
Operational efficiency initiatives
Energy consumption reviews at our largest pumping stations – Hoppers Crossing, Brooklyn, Yering Gorge and inflow pumps and aeration blowers at the Eastern Treatment Plant – have delivered savings through optimised operations. These facilities combined are responsible for more than 60% of our electricity use.
We are also involved with several Government initiatives aimed at conserving energy, waste and water across our operations.
Our membership of the Commonwealth Greenhouse Challenge Plus program has enabled us to establish a strong foundation for future reporting under the Commonwealth’s National Greenhouse and Energy Reporting System.
We develop water management action plans (waterMAPs), which require major industrial, commercial and institutional water-using organisations to assess their water use, identify inefficiencies, prepare an action plan to implement water conservation activities and report on these activities annually.
We also started to develop Environment and Resource Efficiency Plans, which include self-assessments about how to reduce energy, water and waste footprints, at three sites. We are part of the Commonwealth Government’s Energy Efficient Opportunities program, which requires large energy-using businesses to examine factors that influence energy use and identify, evaluate and report publicly on cost-effective energy savings opportunities.