On-ground investigations begin for bioreactor sites

December 18, 2017

The Cassowary Coast will soon be a trial area for bioreactors and other catchment repair technologies to better protect the Great Barrier Reef.

Up to $15 million is being invested in the Wet Tropics Major Integrated Project (the MIP) – and on-ground investigations have begun for repair and treatment trial sites. These have the potential to significantly reduce the load of nitrogen, pesticides and sediment entering the Reef lagoon.

Until the MIP, which is funded by the Queensland Government, there have been no systematic approaches to trialling and monitoring some of the newest repair and treatment technologies, like bioreactors, in the Wet Tropics.

Systems repair expert Mark Bayley recently joined landholders to talk about trial sites.

“At the end of the day, bioreactors are a proof of concept. There’s a question mark over if and how well they’ll work when they’re applied here. We’re definitely in for a journey - but if these do work, we’ve then got a great opportunity to roll them out across the entire reef catchment.”

The effectiveness of the technologies is highly dependent on location and landscape conditions.

In the design phase of the MIP, initial landscape assessments were carried out via spatial analysis. While this is immensely useful in the early stages, getting out in the field and ground-proofing sites is a critical next step.

In the Johnstone basin, six initial potential bioreactor sites were identified around the Liverpool and Cowley areas. Of these, one was deemed suitable for further investigation as a bioreactor site.

MSF Sugar’s Operations Manager for South Johnstone Farms, Alan Cross, said the Cowley location holds the most potential as the success of a bioreactor is very dependent on soil type.

“While the bioreactors don’t work everywhere, for environmental purposes MSF Sugar is always looking at what we can do to contain runoff on our farms and this particular tool is an option that we’re considering.

Bioreactors are shallow trenches that are filled with a carbon source (like woodchips) that intercept groundwater and denitrify it. Denitrification is the microbial process of converting nitrate to gas.

“After some ground proofing, our 4KZ Farm site in Cowley was identified as the best location to trial a bioreactor while our Cowley Farm was best suited to a constructed wetlands trial” said Mr Cross.

Further south, cane farmer Lauri Keto took the team out to his farm in Lower Tully. Conditions of a corner paddock turned out to be better suited for a constructed wetland, rather than a bioreactor.

“Ideally for a bioreactor site we’re looking for a few metres of sand with a clearly defined clay base, and we couldn’t find that here,” said Tully Basin Coordinator Fiona George.

Mr Keto said that whilst a wetland would take more land he was keen to do his bit for the reef.