Turning organic waste into renewable energy by co-digestion

By listening to our customers’ needs, Melbourne Water has maximised the use of existing assets, reduced greenhouse gas emissions, and delivered a new revenuegenerating service, while keeping costs down for customers.

Western treatment plant renewable energy large

Here’s one example:

Melbourne Water customer, City West Water, came to us with a problem. Many of their industrial food customers had organic liquid wastes that were unsuitable for discharging to the sewer, and they wanted to explore ways that these wastes could be treated.

Melbourne Water decided to undertake a trial to see if these waste streams could be used to generate additional biogas at the Western Treatment Plant (WTP). The innovative trial used existing assets, in turn becoming a new source of revenue. We started small with an increase of 1 percent for the existing incoming organic load as this was judged a safe expansion. During the process, waste products were added to the main feed stream into the existing anaerobic lagoons at WTP where they were digested by anaerobic microorganisms to form biogas. The gas production from these lagoons is used to generate renewable electricity to run WTP.

Interest in the service has been so positive that an expansion of the project was required. Melbourne Water is now maximising the production of biogas in the existing anaerobic lagoons at WTP by accepting an increase in organic waste load of up to 3 percent over five days a week.

Last updated:
20 May 2019