Value in waste

Value in waste


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The windrows during the maturation process.

The windrows during the maturation process.

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IT IS compost, but not as you know it. In an innovative project near Sale, Gippsland Water is combining human biosolids with green and industrial waste and producing agricultural fertiliser.

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IT IS compost, but not as you know it.

In an innovative project near Sale, Gippsland Water is combining human biosolids with green and industrial waste and producing agricultural fertiliser.

With an NPKS averaging 18:10:6:4, it is going out the door at a rate of 800 to 1000 tonnes per week.

"It's got a lot of nutrient in it – similar to an NPKS dairy blend," said Gibsons Ground Spreads managing director Damien Gibson – the third generation of his family to run the company started by his grandfather Bill.

"We apply it at phosphorous 4-8kg/ha, potassium 6-8kg/ha and nitrogen 14-20kg/ha, with traces of sulphur, calcium, magnesium, molybdenum, zinc, copper, cobalt, carbon and microbes.

"It's the microbes that make the difference. It suits lighter country that needs organic matter, but it goes on everything."

Mr Gibson is supplying the slow-release fertiliser, called Revive, to farms between Bairnsdale in east Gippsland to Pakenham and Wonthaggi in west and south-west Gippsland.

It is being applied to mainly dairy, beef and sheep farms, but he is seeing growing interest among croppers, vegetable growers and potato farmers.

Gibsons is also running 14 trial plots across Gippsland to measure the fertiliser's effectiveness and yield value.

"We put the trial plots down 12 months ago and we've already seen an increase of 10 in phosphorous levels using the Olsen P test," Mr Gibson said.

"In sandy soils, we've seen changes in the structure to loam.

"Dairy farmers are telling me that applying the compost offsets the acidic residue resulting from applications of high levels of nitrogen.

"They also say it takes about 8-10 weeks before the pasture changes colour and kicks on.

"One dairy farmer's herd is producing 1000 litres/day more milk."

The project has taken four years of development.

It is based at Gippsland Water's Soil and Organic Recycling Facility (SORF) at Dutson near Sale in Gippsland.

Dutson Downs includes a farm and has for many years been a dumping ground for industrial waste.

Gippsland Water began looking at ways to re-use this industrial waste, green waste and human excrement, particularly with a deadline looming that forbids biosolids being sent to landfill.

"We have two categories of waste that get sent here – prescribed and non-prescribed wastes," SORF manager Mark Heffernan said.

"The prescribed wastes include industrial and food wastes and contaminated soils, such as oil spills and hydrocarbon-polluted dirt from petrol stations.

"The industrial wastes come from milk factories and chicken processors, among others.

"Non-prescribed wastes are green waste – we get about 2t/week of lawn and tree clippings from Melbourne's eastern suburbs – biosolids – the end products of sewerage – and sludges out of water treatment practices.

"We get about 600t/wk of sewerage.

"We also get odd things like truckloads of spoiled yoghurt, cheese, spilt milk, broken eggs and chocolate.

"We are starting to get mixed waste from food markets and supermarkets.

"It's all sorted, screened where necessary, put out in rows and mixed.

"The hydrocarbons break down with the other wastes, resulting in increased nitrogen."

Prescribed wastes are initially treated separately, with an intense three-day pasteurisation, before green waste is added.

Non-prescribed wastes go through a four-week pasteurisation phase, in windrows.

Then follows an eight-week maturation process.

Water from acquifers is one of the key ingredients in the project, encouraging bugs to do their work.

The temperature of the windrows is kept between 55-65 degrees, with a moisture level of 40pc.

"It's important to balance the carbon and nitrogen levels in the windrows and the turning process controls the temperature; and we add water as part of the turning process and that also helps control the temperature," Mr Heffernan said.

"The windrows are turned five times in four weeks and the temperature has to be maintained between 55-60 degrees for a consecutive 15 days."

The 40-50 windrows are 200m long and contain 900 cubic metres of green waste and 200-300t of biosolids. This produces 800-1000t/wk of composted fertiliser.

Only a portion is used on the Dutson Downs farm, although initially all the fertiliser was applied to it during the development phase. This was when Gibsons first became involved.

"We got involved as we were spreading Revive on-farm before it was ready for commercial sale," Mr Gibson said.

"We then started working closely with SORF to make sure the product was commercial and at the quality that our farmer clients would expect."

Gippsland Water agribusiness manager Jono Craven has seen for himself the added value of using Revive on the Dutson farm.

"It's one of the reasons we're turning off better weights," he said. "We are also seeing an improvement in soil health."

Mr Craven manages a commercial Angus herd, a flock of sheep, grows 2500ha of pasture and crops canola, wheat, barley and triticale off 700ha.

He manages an additional 1000ha across several farms in Gippsland.

The farms use 10,000-15,000t/pa total of Revive fertiliser, with Dutson using 10,000t.

"We have really sandy soils and Revive is meeting the majority of our nutrient needs," Mr Craven said.

"Our nitrogen application rates are dropping and we're getting better cropping yields, better groundcover and better colour in our pastures.

"The stocking rate has risen from 500 to about 1000 breeders in four years and we're able to turn-off cattle at 22 months at 500kg.

"Four years ago we were turning off animals weighing 420-450kg at the same age. This change has given us more options."

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