Hopes for bioreactor innovation to drive sustainable farming, protect oldest New South Wales marine park

Researchers and local and state agencies are working to improve farm fertiliser management to protect Coffs Coast waterways and the adjacent marine park. (Supplied: Frank Redward)

In a bid to reduce fertiliser pollution entering the oldest New South Wales marine park, Australia's biggest blueberry farming region has trialled an emerging innovation that was pioneered to protect Queensland's Great Barrier Reef. 

In recent years, researchers found high amounts of nitrogen from fertilisers in Coffs Coast waterways, particularly in the Hearnes Lake catchment, where most horticulture farming occurs.

Southern Cross University PhD candidate Shane White and his team estimated the catchment's nitrogen levels were six times higher than the Australian east coast average.

Hundreds of fish and dozens of coral species inhabit the Solitary Islands Marine Park.  (Supplied: Brett Vercoe)

High nitrogen and nutrient levels in waterways can have devastating environmental impacts, including algal blooms, which lead to fish kills.

After rainfall events, the nitrogen levels in the Hearnes Lake catchment were at least 50 times higher than recommended under water-quality guidelines set by the Australian and New Zealand Environment Conservation Council (ANZECC).

The catchment's waterways flow into the Solitary Islands Marine Park, which is home to hundreds of species of fish and dozens of types of coral.

To reduce fertiliser run-off, researchers have been trialling a system called a bioreactor, which has been in use in Queensland to prevent run-off affecting the Great Barrier Reef.

The Coffs Coast in NSW is the country's largest producer of blueberries.  (ABC Coffs Coast: Claudia Jambor)

What is a bioreactor?

A bioreactor is a simple trench, filled with woodchips, and is something that has been proven to catch fertiliser before it gets into waterways.

Naturally occurring bacteria in the woodchips break down fertiliser chemicals and convert them into di-nitrogen gas, which is harmless and makes up most of the Earth's atmosphere.

The bioreactor trials are part of a broader research project being conducted by Coffs Harbour City Council, Southern Cross University and Local Land Services to better manage fertiliser pollution in waterways.

Southern Cross University researcher Shane White (left) and Shaun Morris from Local Land Services inspecting a bioreactor at Sandy Beach.  (ABC Coffs Coast: Claudia Jambor)

Promising results, but no 'silver bullet'

Local Land Services officer Shaun Morris worked with participating farmers to develop two different bioreactors.

The system installed at a blueberry farm in Sandy Beach was similar to those trialled in Queensland, both of which were designed to catch surface run-off.

Woodchips from the bioreactor at Sandy Beach.  (ABC Coffs Coast: Claudia Jambor)

Overall, the prototype was able to reduce nitrogen run-off into waterways by about 30 per cent. When operating at full capacity, pollution was reduced by between 73 and 85 per cent.

For Nicole Strehling, the manager of the Solitary Islands Marine Park, the results are promising.  

One of the region's blueberry growers has been participating in the trial.  (ABC Coffs Coast: Claudia Jambor)

Another bioreactor was constructed to catch the fertiliser-rich run-off coming directly from cucumber plants in hothouses.

The excess was captured and filtered through a network of pipes filled with woodchips to best filter out the nitrogens and stop the production of nitrous oxide gas, which has nearly 300 times the global warming potential of carbon dioxide.

While nitrogen run-off was reduced by 15 per cent, Mr White said it was significant considering his research showed local waterways near cucumber hothouses showed nitrogen levels 28,000 times above the ANZECC guidelines.

Cucumber and raspberry farmer Palwinder Singh trialled a bioreactor on his property at Bucca. ( ABC Coffs Coast: Claudia Jambor)

Modifications have since been undertaken on that bioreactor that are hoped to increase its effectiveness.

Cucumber and raspberry farmer Palwinder Singh hoped the trial on his property would demonstrate the industry was embracing sustainable practices but, he said, more needed to be done.

Construction of a bioreactor for cucumber hothouses in Bucca, NSW.  (Supplied: Local Land Services)

Mr Morris said work was being done to enhance fertiliser application practices. 

"We always try and talk about the fact that [bioreactors are] not a silver bullet," Mr Morris said.

In future, Mr White said, it was hoped the lessons from these trials would help enable further studies into bioreactors, which could play a big role in protecting waterways and marine parks.  

"And then we can really protect our waterways and stop greenhouse gas emissions."

The Solitary Islands Marine Park is the oldest in New South Wales. (Supplied: Brett Vercoe)

Keeping costs down

Mr Morris said minimising the costs of a bioreactor was a big priority and would encourage farmers to install them in future. 

"We've tried to use materials in our bioreactors that are economic and accessible to keep that cost down and make these structures far easier to build," he said. 

The structure at Bucca cost about $25,000, which is cheap compared to alternative nutrient management systems such as commercial septic systems, which cost roughly $100,000.

Solitary Islands Marine Park manager Nicole Strehling says the trials are a positive step. (ABC Coffs Coast: Claudia Jambor)

Back in the Solitary Islands Marine Park, Ms Strehling said the trials were a positive step toward a better balance between farming and protecting marine life.