Biosolids are the nutrient-rich organic material produced after wastewater has been treated and stabilised. Far from being a waste, they are a by-product with significant agronomic and environmental value.
In Australia, most biosolids are beneficially applied on land, where they provide essential nutrients, improve soil structure, increase microbial activity, and boost resilience in farming systems.
By recycling carbon, nitrogen, phosphorus, and micronutrients back into the soil, biosolids reduce reliance on synthetic fertilisers, many of which are costly, energy-intensive to produce, and subject to volatile international markets and supply chains. As a steady, locally available resource, biosolids also underpin circular economy ambitions.
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A resource under pressure
Biosolids have long been recognised as a valuable resource, but the sector is now at a crossroads. While the benefits of biosolids are widely acknowledged, their continued use faces a complex mix of challenges including contaminants (such as per- and polyfluoroalkyl substances (PFAS)), increasingly conservative regulatory reform, rising transport and processing costs, and mounting scrutiny from communities and markets.
Population growth and urbanisation is amplifying these pressures, increasing biosolids production and forcing utilities and regulators to adapt.
Building a shared vision
Two major initiatives are shaping an updated, national perspective on biosolids management.
qldwater’s Future of Biosolids Reuse Roundtable brought together utilities, regulators, agricultural users and scientific advisors. The consensus was clear: land application remains the cornerstone of biosolids use. It delivers consistent agronomic benefits and supports resilient farming systems, especially as fertiliser costs and carbon decline in soils weigh heavily on farmers. Participants also emphasised practical constraints: odour, seasonal application windows, logistics, and the growing burden of regulatory uncertainty.
WSAA’s “Weighing up the Options” Sustainable Biosolids Management Assessment provided a structured comparison of 20 different management pathways. It found that where PFAS risks are managed land application continues to deliver the best outcomes, while advanced anaerobic digestion, pelletisation, pyrolysis and gasification represent viable alternatives should land use be restricted.
These sector-led initiatives have set the foundation for a holistic vision: optimisation of existing practices, diversification into emerging technologies, and stronger source control of contaminants.
Outcomes and priorities
From these initiatives, several clear priorities emerged:
- Recognition of biosolids as a resource, not a liability.
- Maintaining land application as the primary use pathway, supported by policy reform and improved logistics.
- Diversifying into advanced technologies like digestion, pelletisation, and thermal conversion to build resilience.
- Tightening source control of contaminants, particularly PFAS, to secure long-term viability.
- Creating viable markets for biosolids and derived products, including opportunities in soil carbon and the recovery of non-renewable, essential nutrients many of which are rare.
This collective vision calls for an adaptive, risk-based approach that balances opportunity with precaution.
NSW Biosolids Regulatory Review: Concerns over proposed limits
The national conversation has gained new urgency with the ongoing NSW Biosolids Regulatory Review.
The NSW EPA’s draft Biosolids Resource Recovery Order/Exemption proposes the introduction of conservative contaminant limits for PFAS (more conservative than the advice in PFAS NEMP 3.0), which has raised alarm across the sector.
The order also telegraphs future limits for HHCB and triclosan: compounds that are widely used in household products. Water utilities are passive receivers of these community-derived contaminants.
Utilities and agricultural stakeholders fear the thresholds under consideration are overly conservative and out of step with risk-based international practice.
They argue that, if adopted, these limits could sharply reduce the proportion of biosolids eligible for land application, without consideration of risk-based scientific evidence of environmental or health impacts as outlined in the PFAS NEMP 3.0.
The PFAS NEMP itself cautions that exceedance of “trigger” values does not necessarily imply unacceptable risk.
If the existing soil plus added biosolids PFAS would exceed those levels, then constraints need to be placed (e.g. limiting application rate) or further risk assessment/management is required.
The stakeholders say the adoption of more restrictive trigger values will not necessarily provide improved environmental outcomes and may indeed yield disbenefits for the agricultural sector. The concern is not simply regulatory compliance: it is the wider implications and that more restrictive limits could:
- Undermine agricultural confidence, despite decades of sustainable use.
- Erode market access, shrinking the outlets available to utilities.
- Drive higher costs, with utilities forced to invest in advanced thermal or disposal solutions before markets and policy are ready.
- Diminish circular economy gains, cutting off a stable, carbon-rich soil amendment in favour of higher-cost, less sustainable pathways and forcing technology adoption which may destroy the opportunity to recover the non-renewable essential nutrients.
For the Directorate, the solution lies not in fatiguing utilities but in addressing source control of contaminants. Without upstream regulation of industrial inputs and consumer products, limits on biosolids alone risk being both ineffective and economically damaging.
The outcomes from the NSW Biosolids Regulatory Review is a reminder that poorly calibrated policy has the potential to destabilise an entire use market. For many, it underscores the urgent need for nationally consistent, proportionate, and evidence-based standards.
Looking ahead
Developing a holistic vision for biosolids management is no longer optional. It requires:
- Adaptive frameworks that integrate risk, opportunity, and community expectations.
- Coordinated reform across resources, environment, and agricultural policy.
- Greater investment in innovation to ensure technology pathways are commercially viable.
- Building and maintaining social licence with farmers, regulators, and the public.
The future of biosolids will depend on aligning innovation, regulation, and market development. Land application will remain central, but it cannot stand alone. A resilient system will be one that blends optimisation of existing practices with investment in new technologies, while tackling contaminants at their source.
The Queensland and WSAA initiatives show the way forward: collaborative visioning, evidence-based evaluation, and proactive diversification.
The NSW EPA’s draft Biosolids Resource Recovery Order/Exemption demonstrates the fragility of progress.
Without proportionate regulation and strong source control, the sector risks being pushed into costly, less sustainable alternatives.
By taking a national, adaptive approach, Australia can ensure biosolids remain a cornerstone of sustainable water management and agricultural resilience rather than an unintended casualty of regulatory overreach.
For more information, visit qldwater.com.au