Sydney Water committed to sustainable energy projects

Along with the provision of world-class water and wastewater services, protection of the health of our customers and protection of the environment are part of Sydney Water’s core values.

Sydney Water has reduced its carbon and ecological footprints by 45% and 35%, respectively, since 2007–08. This has been achieved despite an increasing population and the need for more energy-intensive water sources.

Pumping and treating water and wastewater uses large amounts of energy. Sydney Water recognises the sustainability benefits in producing our own power on-site and exporting some to the electricity grid. In doing this, we produced 72,600 MWh in 2014–15, which is enough energy to power around 10,000 homes each year. Of this, we exported 6000 MWh to the electricity grid.

Operationally, Sydney Water is already generating more than 17% of its total energy use through an extensive portfolio of renewable energy projects. This reduces greenhouse gas emissions by over 60,000 tonnes a year.

Through our innovation, we continue to keep electricity purchase to below 1998 levels.

Case study: Bondi Wastewater Treatment Plant

The Bondi wastewater treatment plant became a net energy producer last year. Generation of electricity in 2015, through the co-digestion process, exceeded electricity demand by 13%.

Co-digestion is still in its infancy in Australia, but the results of Sydney Water’s Bondi Glycerol Pilot Project have exceeded expectation by leveraging international best practice — with the potential to double our biogas production. We use biogas to generate green energy from waste.

In 2012 we built two 50 L digesters at Bondi that were used for testing glycerol co-digestion. Glycerol is the waste by-product from the production of biodiesel. This work showed that by adding just 2% glycerol to wastewater received at the plant, we could double biogas production.

We commenced a pilot project at our Bondi wastewater treatment plant in October 2014 to co-digest up to 600,000 L of glycerol with wastewater sludge. So far we have processed 220 kL of waste and produced 440 MWh of additional renewable energy.

Our long-term 2020 plan is to provide a service for most or all organic waste streams for our customers. Our audit of waste streams identified two streams that provide the best combination of benefits, risk management and potential long-term scale — beverage waste and glycerol.

Sydney Water will deliver one new co-digestion pilot project per year over the next three years, with larger scale commercialisation planned from 2020.

We recently commenced work on a collaborative co-digestion research project with Wollongong University, which is supported by the Australian Research Council. As part of this, two 1000 L research digesters were built, to be located at Shellharbour wastewater treatment plant. This work will help to optimise the value of co-digestion by determining maximum feed.

A second pilot project taking pulped fruit and vegetable waste will commence at Cronulla in early 2016.

Sydney is preparing for additional pilot projects to process wastes such as beverage waste, dairy, bakery and fats, oils and grease.

With this work, Sydney Water is aiming to set a new standard for resource recovery in the Australian Water Industry. The projects leverage our expertise and infrastructure for processing liquid organic waste and turning it into usable resources — energy and biosolids fertiliser. These projects will also help reduce our environmental impacts and the transportation of wastes.

The NSW Office of Environment and Heritage (OEH) recognised the value of Sydney Water’s work to date and future plans for co-digestion by providing a $150,000 grant in 2014.

Sustainable stepping stones

Sydney Water aims to set and achieve enhanced targets in the quality of Sydney’s environment and in the provision of services to meet both customer and community expectations.

We are using hydro-power generation at North Head wastewater treatment plant, on the Warragamba pipeline, and a pipeline from Woronora Dam. These hydro power plants use pressure reduction and gravity flow in water and wastewater streams to generate energy.

We continue to keep electricity purchase to below 1998 levels and know we will continue to achieve this cost-effectively through the use of our purpose-built Cost of Carbon Abatement Tool. The tool was developed to standardise and simplify the assessment of carbon mitigation opportunities. It helps us determine the potential greenhouse gas volume reductions and identify the most economical forms of abatement investments.

Solar energy

In 2008/9, Sydney Water investigated the use of solar power plants to increase renewable energy generation on its sites. The outcome was a 60 kW pilot plant built in 2009 on the roof of our Potts Hill warehouse. No further solar plants were considered until 2013 as the projects were not financially viable. However, a 70% drop in construction, supply and installation costs for solar power has significantly improved the project economics. Since 2015, eight solar plants totalling 100 kW have been commissioned across eight Sydney Water sites.

Modelling

Sydney Water has now assessed around 1700 sites for their solar suitability. An in-house assessment tool is used to model and re-model sites for their financial viability in future. It is expected that solar prices will continue to fall, although not as rapidly as between 2008 and 2015. This will further increase the attractiveness of this kind of renewable energy generation for Sydney Water. The federal government’s renewable energy incentive — Small Scale Technology Certificates or STCs — is another criterion facilitating solar plant rollout across Sydney Water sites.

Selection criteria for Sydney Water’s solar plants

To find the most suitable sites across Sydney Water, the following selection criteria were assessed:

• Heritage permissions to install a solar plant were sought from Sydney Water’s heritage department.
• Orientation to the north.
• No shading from trees.
• An on-site load is required to take the produced power instead of exporting it to the grid; this ensures faster amortisation periods as the price for exported power is much lower than for power imports.
• Sufficient roof space.
• Is the site prone to vandalism?
• Are future upgrades of the roof or building planned, potentially shortening the period in which the plant can be amortised?
• Acceptable amortisation periods.

A variety of sites (eight sites in total) were chosen, allowing Sydney Water to gather experience with different roof designs.

Future projects

Sydney Water will continue to investigate projects to minimise our carbon and environmental impact while at the same time providing the services that our customers demand.

Future solar power opportunities are currently being investigated.

What is exciting is the opportunity to utilise a series of different products, currently considered to be waste, as a resource to generate additional power through our co-digestion processes at wastewater treatment plants.

This will have a significantly positive impact in reducing the waste stream while at the same time creating a green alternative to power production.