Farmer demand for Sydney Water’s biosolids program – which turns human waste into nutrient-rich fertiliser – is currently outstripping supply.
The program, which has now been running for 20 years, is known to increase crop yields by 20-30%.
Sydney Water produces upwards of 180,000t of biosolids each year, with 70% applied across 20 broadacre cropping and livestock farms in the Central West and South West of NSW. The rest is either composted or used for mine rehabilitation.
“We’re converting what has traditionally been seen as a waste product and turning it into a valuable resource,” said Gavin Landers, Operations Contracts Manager at Sydney Water
Landers said the program has also benefitted Sydney’s waterways and surrounding oceans, which were the previous destination of huge volumes of human waste. “We’re closing the organic and nutrient loop between city and farm,” he said.
Where synthetic fertilisers applied on paddocks will give soil a quick fertility boost, biosolids “enable large quantities of nutrients to be placed safely into the soil and utilised as the plants need them over a number of years,” said Roger Crisp, an Agronomist for ANL – one of three biosolids contractors for Sydney Water.
Treated crops are also “more resilient in colder conditions, respond quicker and for longer after rain and are less prone to disease,” said Crisp.
Although the initial layout cost may be steep for some properties, biosolids are a cheaper alternative to conventional fertiliser after a four-year period. Some croppers have eliminated the need to apply synthetic fertiliser for up to three years, and reduced the need for the three years following.
Crisp said that, on average, croppers using biosolids have reduced input costs by between $200 and $300 per hectare per year for up to five years.
Alongside the benefits for farms and waterways, Sydney Water has also reduced its pressure on the grid, with the energy by-product from biosolid processing powering 21% of related operations.
The wattage is enough to power 11,000 homes and cut greenhouse gas emissions
by over 70,000t per year.
Beginning as ‘sludge’, human waste is collected at Sydney Water’s 23 wastewater treatment plants, where it is screened, settled and baked in digesters for a minimum of 20 days.
Over 30 years of research has shown no adverse environmental or human health impacts stemming from the use of biosolids
The source of biosolids “may be perceived as dark and mysterious,” said Crisp, “but its final destination is certainly brightening the outlook for those farmers fortunate enough to receive it”.
Next time they flush, Sydney residents should take heart knowing they are sending Sydney Water a package that could benefit farmers, the environment and themselves.