Solar Powering Karragarra Island Composting Trial

It’s hoped solar energy will help residents of Karragarra Island in Brisbane’s Moreton Bay better deal with organic food waste.

Situated in the southern part of Moreton Bay, Karragarra Island covers around 240 hectares and is home just to couple of hundred people. While a very small population, 16,000kg of organic food waste is generated a year that is transported back to the mainland according to Redland City Council.

A collaboration between Council, University of Queensland’s Centre for Recycling of Organic Waste and Nutrients (CROWN) and several local community groups is seeking to help address the situation through the use of a solar-powered composting system; the idea for which came from California-based Conscious Compost.

The system includes a pair of solar panels that charge a bank of lithium-ion batteries, with the stored energy used to power a time-switch operated blower. The blower pushes air through sub-surface pipes to the base of compost bays, which is drawn up into the material through convective currents generated by heat created in the composting process.

There wasn’t an image available of Karragarra Island’s aerated static pile system, so here’s one from the Conscious Compost website:

Decreasing Waste Shipped, Increasing Self-Sufficiency

Residents signing up for the trial are provided kitchen caddies and compostable liners they empty into larger bins situated at the island’s jetty and the Karragarra Community Garden. Once processed, the resulting compost will be used for the Community Garden.

“If more organic food waste can be retained for beneficial use within the island communities, it will not only be a great saving to Council but a clever way for islanders to become more self-sufficient as food growers,” said Councillor Mark Edwards.

25 households had signed up for the trial as at last week and it’s hoped a total of 50 will join. If the trial is a success, the system may be implemented on other Redlands Coast islands.

Redland City Council noted that in 2019, approximately 7,321 tonnes of organic material (not just food waste) was collected from the islands, including about 235 tonnes from Karragarra. This was all shipped to the mainland, at considerable cost to Council.

Solar Energy On Moreton Bay’s Islands

Residents of Moreton Bay’s islands are already pretty switched on to the benefits of solar power, and this project is yet another application for it.

Solar panels are a common sight on the rooftop of homes on Karragarra, Coochiemudlo, Lamb, Macleay Island, and Russell islands. In the 4184 postcode – which covers all of these locations – 2,305 small-scale solar power systems had been installed as at the end of February this year; an impressive tally given a total population of approximately 6,300.

More broadly across the Redland City Council local government area, which also covers suburbs including Capalaba and Alexandra Hills, there had been an estimated 30,600 solar installations as at the end of December last year. APVI estimates a whopping 49.7% of Redland City LGA dwellings had panels installed at that point.