The state of biosolids in Australia and the US

Waste Management Review looks at the lessons learnt from biosolids in the US and Australia to improve soil health and composting. 

What do Bill Gates and human waste have in common?

In recent times it seems a whole lot, as the billionaire philanthropist has spent US $200 million over the years to generate new approaches to toilet technologies and transform human waste into fertiliser, recycled waste or energy. 

The end result has potential to boost productivity, save money, preserve precious resources and support developing countries. In 2011, the Water, Sanitation & Hygiene program initiated the Reinvent the Toilet Challenge to support 2.5 billion people worldwide that don’t have access to safe, affordable sanitation. 

The Reinvent the Toilet Challenge aimed to create a toilet that could remove the germs from human waste and recover valuable resources such as energy, clean water and nutrients at a low cost. Gates is now testing further prototypes in poor, urban communities in India and Africa. Composting toilets provide waterless decomposition of organic matter to transform that into compost and can be used in dry landscapes and areas with low rainfall or minimal access to water. 

Chuck Henry, international consultant and design engineer, was involved in the design and licensing of two composting toilets, in addition to monitoring and evaluating large-scale compost systems, wastewater treatment, renewable energy and solid waste management. 

He and his partner Sally Brown, a research professor at the School of Environmental and Forest Sciences at the University of Washington, were keynote speakers at this year’s Australian Organics Recycling Association (AORA) Annual Members’ Meeting Forum.

Sally and Chuck’s research has found significant potential of human excrement to improve our natural resources. In Australia and other developed countries, a more mainstream solution in the form of biosolids have for decades been used to improve soil fertility. Sewage sludge is a by-product of treating wastewater from humans. When treated to an acceptable standard, the waste becomes a biosolid which may contain macro and micronutrients. But there is much untapped potential in their application overseas and in Australia, which Waste Management Review has sought to explore further.  


Sally has specialised in biosolids and organic residues and their potential to improve soil fertility and a number of other properties important for plant growth. Her research looked at how soils applied to residuals may also store more carbon, which can assist in mitigating climate change. In addition to in-situ restoration of contaminated sites, Sally’s research looked at the concept of integrating residuals into green urban infrastructure. The University of Washington research has begun to work on establishing the strength of nitrous oxide emissions from organically amended soils. 

Chuck tells Waste Management Review that his passion for biosolids dates back to the 1980s.

“I went to a conference on putting sludge in forest land and I was so enamoured by the whole process and the results I signed up to do my doctorate,” he says.

“From there, I did a lot of research in forest applications and it transitioned into research in compost. I was involved in national regulation development for contaminants and in the last 10 years or so I’ve transitioned even further into composting toilets.” 

Sally says that her 30-year research journey began with Chuck reclaiming the most contaminated sites on the US EPA Superfund list, a list of national priority sites at risk of hazardous substances or pollutants. From there, Sally worked on areas of carbon accounting and has now moved onto biosolids in urban areas. 

She says that following decades of research, significant changes are now starting to occur. 

“I think that cities are understanding more and more you have public health protection for waste treatment as the first goal, then environmental protection and resource recovery,” she says.

“The big discrepancy I see are people are really into the environment. People are really into the concept of compost, but you have regulations to make sure you don’t poison anything and make sure a product is used and integrated into society.” 


One 2009 research paper titled Land Application – a true path to zero waste, estimated that each person in Washington State creates about 60 pounds (27 kilograms) of biosolids, about the same amount of food waste and about 150 pounds (68 kilograms) of yard waste each year. 

The studies took organic amendment residuals to test their performance. Soil samples for the study included long-term replicated field trials and farmers fields distributed across Washington State and a range of land uses, including turf, ornamental crops, highways, agronomic crops and high value orchard crops such as pears, cherries and hops. 

The results showed all studies using organic amendments resulted in significant increases in soil carbon storage. Carbon content in soils increased with time, which found organic matter added with the residuals application resulted in long-term carbon increases in soils. 

In terms of benefiting the soil itself, all studies showed total nitrogen in soils that received organic amendment addition was higher than conventionally fertilised or control soils for at least one of the rates of amendment tested. Soil physical properties also generally improved, in addition to soil water holding capacity in five of the nine sites sampled and reduced bulk density in a number of sites.

Another study, titled Changes in soil properties and carbon sequestration potential as a result of compost or mulch application: Results of on-farm sampling, used a lifecycle analysis on open windrow composting to quantify the benefits of applying compost to agricultural soils in California. The project looked to investigate the impact of applying compost produced using municipal food and garden waste to agricultural soils. The limited field sampling found improvements were greater than the lifecycle analysis, including greenhouse gas equivalencies and water savings and improvements in soil quality and plant yield. 

Sally says that more municipalities are using biosolids in the US and being upfront on what they contain.  

“The industry for a very long time had a real philosophy if we stay on the down low, real quiet, no-one will say anything and it will be OK. That backfired at least in the US and developed a lot of mistrust and people thought we were trying to hide something,” she says.

“One of the big concerns or challenges are that you’re dealing with a municipal infrastructure that is very used to having to abide by regulations and meet permits and not cause a fuss, but you’re not dealing with an entity that’s used to developing a product that’s marketed and understanding how to meet a customer’s demand.”

Chuck says that in the US, compost is much more easily accepted than biosolids. However in Seattle, Sally says that biosolids branded Loop are being used effectively. Loop has been used in a range of locations in King County, Washington, including Boulder Park, the Snoqualmie Forest and the Washington State Department of Natural Resources. Sally says Chicago is now also distributing and selling biosolids to homeowners.


In Australia, biosolids are largely limited to agricultural applications, energy recovery, road base, land rehabilitation and landscaping. Biosolids are also mixed in with organic waste in composting. 

According to the Australian & New Zealand Biosolids Partnership, in 2017, Australia produced about 327,000 dry tonnes of biosolids annually. About 75 per cent of this was applied to agricultural land and about 19 per cent used for landscaping or land rehabilitation and the remaining stockpiled, landfilled or discharged to the ocean. 

The organisation on its website notes Australia has one of the strictest regulatory regimes for biosolids production and application in the world. It notes that biosolids may contain traces of synthetic organic compounds and metals, including arsenic, cadmium, chromium lead, mercury, nickel and selenium, limiting the extent to which biosolids can be used.

Biosolids are classified in specific state, territory or national guidelines and must be tested to ensure they meet the quality standards defined in the respective state, territory and national guidelines.

For example, in WA, the state government guidelines for biosolids management indicates biosolids are used on select agricultural and forestry properties and in compost production. According to data from VicWater, Victorian water utilities beneficially reuse about 26 per cent of the biosolids produced in the state.  

As state and territory water authorities process Australian wastewater, companies such as Sydney Water, Melbourne Water, TasWater and SA Water all have their own biosolids processing. 

For example, Sydney Water has a $25 million biosolids program and produces about 180,000 wet tonnes per annum for reuse in agriculture.

In Victoria, there are numerous water businesses that treat their own biosolids through a composting process to be re-applied to agricultural land to benefit the soil quality and ultimately improve productivity. 

To the east of the state, Gippsland Water processes up to 25,000 tonnes of biosolids per annum, mixing it with a number of other organic streams and composting it, ultimately achieving compliance with Australian Standard AS4454. 

This compost product is commercially distributed predominantly to the broad acre farming industry.

Kelly Hopewell, Chair Australian New Zealand Biosolids Partnership (ANZBP), says that in Australia, a stigma exists on the public perception of biosolids, despite being used safely for more than 30 years. 

ANZBP was created to promote and support the sustainable management of biosolids in Australia and New Zealand and its advisory board includes representatives from from SA Water, NSW EPA, Sydney Water, TasWater and Queensland Urban Utilities. 

ANZBP’s members comprise consultants and contractors that apply the materials to land. It also has strategic alliances with AORA and other water associations. 

One of the barriers, Kelly says, is the perception that biosolids should not be applied to agricultural land where food is being grown. The Harmonised Australian Retailer Produce Scheme (HARPS) indicates that treated and untreated fertilisers and soil additives made from biosolids are not permitted for use on growing sites or potential growing sites. Kelly says there is potential for this exemption to be removed when HARPS updates its guidelines to bring them in line with current biosolids guidelines. 

In addition to chairing the partnership, Kelly is also the Coordinator of Process Engineering helping to optimise the sewage treatment plants for a local government in South-East Queensland. In Queensland, a number of councils run their own water services, contrary to the other states and territories with government-owned water businesses. Kelly says that having the council run its water and waste businesses has provided it with synergies and insights into managing its waste business. 

While biosolids have been largely used on agricultural land, Kelly says potential exists for the councils to look at applying them to council-run land. She says infrastructure projects could also utilise biosolids. 

One of the emerging contaminants which will need to be updated in biosolid guidelines is per- and poly-fluoroalkyl substance (PFAS) chemicals, historically used in firefighting foams and other industrial and consumer products. 

The ANZBP is working closely with other industry bodies and the National Chemicals Working Group, a working group of environmental regulators from all state and territory governments and the Federal Government, to ensure that biosolids are considered in the next version of the PFAS National Environmental Management Plan.

Kelly says that ultimately the key will be to try and stay ahead of the game with emerging contaminants and ensure regulations are up-to-date and relevant. 

She says there is also room to improve communication that biosolids are beneficial to farmers and the community. 

She says the benefits are not just applicable to carbon sequestration, but in avoiding the energy intensive process of producing chemical fertiliser.

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