Wastewater Treatment Plants and Cogeneration - Is there value?

Wastewater treatment plants aren't generally something you speak about in everyday conversation, nor are they something that you would likely consider when looking at creating eco-friendly energy. But cogeneration can potentially change this approach, and Sydney Water are at the forefront.

Cogeneration

Sydney Water are the perfect an example of the use of biogas to operate cogeneration assets. They have been doing this since 1999, producing up to 15% of Sydney Water's energy needs through the cogeneration process. But is there really value? We take a look below.

The cogeneration plants installed by Sydney Water have a capacity to generate over 60,000 MWh electricity per year thereby reducing over 60,000 tonnes of greenhouse gas emissions, which is the equivalent of removing 15,000 cars from the road.

A little more information to start

  • Biogas is created at wastewater treatment plants across Sydney in anaerobic digesters.
  • The biogas that is produced contains between 55-65% methane.
  • Sydney Water utilises cogeneration in 8 wastewater treatment plants.
  • The installed capacity of the entire system is 9.8MW.

How does it work?

Sydney Water utilises the biogas that is created by wastewater treatments across Sydney to create energy that is used to meet up to 15% of their overall power needs.

Aspects to consider

There are a range of aspects that are required to be considered when it comes to cogeneration and wastewater treatment plants, including:

  • What engine size is practically and financially viable e.g. engines below 200kW are usually not financially viable for Sydney Water.
  • Site factors have be considered and factored in where necessary, including corrosion, emission requirements, access and maintainability of engines.
  • Maintenance costs.
  • Operator capabilities.
  • Stakeholder involvement, if any.
  • Biogas supply/optimisation and measurement.
  • Maintenance strategies that are suitable to the circumstances.
  • Auxiliary equipment costs.
  • Realistic downtime.
  • Cogeneration units that are run on biogas do not all respond the same, therefore different maintenance needs must be met depending on engine model and biogas composition.
“Identifying additional value from cogeneration assets beyond financial benefits from electricity production is a valid approach. A focus on optimising gas production can lead to better biosolids management” - Alex Sanbrook, Renewable Energy Generation Manager at Sydney Water.

These are not negative factors, however they need to be thoroughly understood to ensure the cogeneration arrangement is being utilised to the best of its ability. This is where experts such as Inoplex can assist.

Benefits of cogeneration

So, what benefits does cogeneration offer when used by wastewater treatment plants?

  • Financial benefits due to decreased electricity costs.
  • Green commodity value.
  • Provides a 'hedge' against future power cost increases.
  • Increased plant performance.

Is there value?

Overall, there is significant value in cogeneration when it comes to wastewater treatment plants. While it is noted that the primary benefit is financial in nature, ongoing value from cogeneration also extends to the environment and plant performance too!

Inoplex

If you would like to know more about cogeneration and how much value it can bring to your business, give Inoplex a call on 0448 307 282 and we can discuss your needs now.

Resources:

Utility Magazine (Turning waste into energy: is there value in cogeneration?): https://utilitymagazine.com.au/turning-waste-into-energy-is-there-value-in-cogeneration/

Is there value in cogeneration?: http://www.awa.asn.au/documents/096%20ASanbrook.pdf