Putting AS4454 to the Test:
What Can We Learn from International Compost Standards?

Introduction

Compost quality standards play a critical role in ensuring the safety, effectiveness, and marketability of recycled organic products. In Australia, the voluntary Australian Standard AS4454-2012 has been the benchmark for compost quality for over two decades. However, as the organics recycling industry evolves, questions are being raised about the adequacy of AS4454 in light of changing feedstocks, technologies, and market expectations.

To inform this ongoing dialogue, the Australian Organics Recycling Association (AORA) has published a comprehensive review comparing AS4454 with international compost standards. The paper, titled "International Comparison of the Australian Standard for Composts, Soil Conditioners and Mulches (AS4454-2012)", provides a detailed analysis of the key similarities and differences between AS4454 and standards in Europe, North America, and other regions. It also explores emerging challenges and opportunities for compost quality management in Australia.

This article aims to summarise the key findings and insights from the AORA paper and consider their implications for the future of AS4454 and the organics recycling industry in Australia. It will delve into a comparative analysis of AS4454 and its overseas counterparts, explore key challenges and opportunities, and highlight the pioneering work being undertaken by Australian companies like Huum in advancing compost science and technology. The goal is to spark a constructive and evidence-based conversation about the future of compost quality standards in Australia.

"Despite its voluntary nature, AS4454 has played an important role in driving improvements in compost quality and consistency over time."

Key Findings from the AORA Paper

The AORA paper provides a comprehensive review of the history and current state of compost quality standards, both in Australia and internationally. It traces the origins of these standards back to Europe in the 1980s, where they were first developed to differentiate between high-quality composts produced from source-separated organic wastes and lower-quality products derived from mixed municipal solid waste. This early work laid the foundation for modern compost standards, which aim to ensure product safety, quality and consistency while promoting the sustainable recycling of organic wastes.

Fast forward to today, and AS4454 has become the benchmark for compost quality in Australia since its introduction in 1999. The standard sets out minimum quality criteria for composts, soil conditioners and mulches, covering key physical, chemical and biological parameters such as nutrient content, heavy metal limits, pathogen levels and impurities. Importantly, AS4454 is a voluntary standard, meaning that compliance is not legally mandated. Instead, composters can choose to self-declare their conformance to the standard or seek independent third-party certification.

The AORA paper reveals that while many Australian composters follow AS4454 to some extent, relatively few pursue full third-party certification. The costs and complexity of certification are cited as major barriers, particularly for smaller operators and those producing bulk products for low-margin markets. As a result, the majority of composters rely on self-declaration or second-party certification (e.g. by customers) to demonstrate their adherence to AS4454.

Despite its voluntary nature, AS4454 has played an important role in driving improvements in compost quality and consistency over time. The AORA paper includes a detailed comparison of AS4454 requirements with compost standards and regulations in other key jurisdictions, including Europe, North America and New Zealand. This analysis shows that AS4454 stacks up well against international benchmarks, with broadly equivalent limits for key contaminants like heavy metals and impurities.

In some areas, AS4454 actually goes beyond international standards. For example, the AORA paper notes that AS4454 covers a broader suite of organic contaminants than most overseas standards, including pesticides, herbicides and PCBs. This reflects a precautionary approach to managing potential risks from legacy agricultural and industrial chemicals. However, the paper also suggests that some of these parameters may no longer be relevant and could potentially be removed from the standard to streamline testing requirements.

Another notable finding from the AORA paper is the emergence of new approaches to setting limits for physical impurities like plastics, glass and metals. Traditionally, these limits have been based on weight, with a maximum allowable percentage of impurities by mass. However, some jurisdictions are now moving towards area-based limits, which take into account the size and shape of impurities as well as their mass.

The best example of this is Germany, which introduced an additional area-based limit for impurities in its compost standard in 2018. Under this approach, the surface area of impurities must not exceed 15 square centimetres per litre of compost, in addition to meeting the existing weight-based limit of 0.5% by dry mass. The rationale for this change was to drive further reductions in plastic contamination, recognizing that lightweight plastic films can have a disproportionate impact on compost quality and aesthetics compared to heavier impurities like glass and stones.

The AORA paper also delves into the complex issue of microplastics in composts and other recycled organic products. Microplastics are tiny plastic particles less than 5mm in size that are increasingly being found in the environment, including soils and waterways. While composts and other organic soil amendments are not the main source of microplastics in the environment, they can potentially contribute to the problem if not managed properly.

The paper notes that research on microplastics in composts is still in its early stages, with limited data available on their prevalence, fate and impacts. However, some studies have detected microplastics in composts and other organic soil amendments, particularly those derived from food wastes and biosolids. The levels of microplastics found vary widely depending on the feedstocks used and the processing methods employed, but can range from a few particles to several thousand particles per kilogram of product.

The potential risks of microplastics in composts are not yet fully understood but could include impacts on soil health, plant growth and human health if present at high levels. The AORA paper suggests that more research is needed to better characterise the sources, fate and impacts of microplastics in composted products, and to develop appropriate testing methods and management strategies. In the meantime, the paper recommends that composters take steps to minimise plastic contamination in their feedstocks and products, such as through better source separation and screening processes.

Overall, the AORA paper paints a picture of an evolving regulatory landscape for compost quality in Australia and around the world. While AS4454 provides a solid foundation, there are opportunities to further refine and harmonise the standard over time, drawing on international best practices and the latest scientific evidence. Key areas for future focus include aligning contaminant limits with risk-based assessments of agronomic and human health impacts, adopting area-based limits for physical impurities, and developing validated methods for testing microplastics and other emerging contaminants.

At the same time, the paper highlights the ongoing challenges of balancing the costs and benefits of compost certification, particularly for smaller operators and those serving bulk markets. Overcoming these barriers will require a collaborative effort between industry, regulators and end users to build demand for certified products and create a level playing field for all composters. By working together to continuously improve standards and practices, the organics recycling industry can enhance the quality, safety and reputation of its products while supporting the transition to a more sustainable and circular economy.

Challenges and Future Considerations

While AS4454 has undoubtedly played a vital role in promoting compost quality and safety in Australia, the AORA paper identifies several challenges and opportunities for the standard going forward. One of the most significant challenges is the voluntary nature of the standard, which means that adoption and compliance are essentially optional for composters. This has led to a patchwork of certification practices across the industry, with some operators pursuing full third-party certification, others relying on self-declaration or customer audits, and some not explicitly aligning with the standard at all.

The costs and complexity of third-party certification are often cited as major barriers to wider adoption of AS4454, particularly for smaller operators and those producing bulk products for low-margin markets like agriculture and land rehabilitation. The AORA paper notes that the direct costs of certification can run into the thousands of dollars per year, depending on the size and scope of the operation. These costs can be difficult to justify for producers who are not seeing a clear market demand or price premium for certified products.

Beyond the direct costs, the process of preparing for and undergoing certification can also be time-consuming and resource-intensive, requiring significant investments in record-keeping, testing, and quality control systems. For some operators, particularly those with limited staff and expertise, these requirements can be daunting and may discourage them from pursuing certification.

To address these challenges, the AORA paper suggests that there may be opportunities to streamline and rationalise the certification process, while still maintaining the integrity and credibility of the standard. This could involve developing more flexible and modular certification options that are tailored to the needs and risk profiles of different types of composters and markets. It could also involve exploring alternative certification models, such as group certification schemes or risk-based approaches that focus on critical control points rather than exhaustive testing of end products.

Another key challenge identified in the AORA paper is the need to keep AS4454 up to date with evolving scientific knowledge and best practices. The paper notes that some of the organic contaminants currently covered by the standard, such as organochlorine pesticides and PCBs, are legacy chemicals that are no longer in widespread use. While it is important to monitor for these substances, the paper suggests that there may be scope to rationalise the list of parameters over time, based on a risk assessment of the likelihood and consequences of their occurrence in contemporary compost feedstocks.

At the same time, the AORA paper highlights the emergence of new contaminants of concern, such as microplastics, that are not yet fully addressed by AS4454 or other compost standards around the world. As mentioned earlier, microplastics are tiny plastic fragments that are increasingly being found in the environment, including in soils and composts. While the risks of microplastics are not yet fully understood, there is growing concern about their potential impacts on soil health, food safety, and human health.

The AORA paper notes that research on microplastics in composts is still in its early stages, with limited data available on their prevalence, fate, and impacts. However, some studies have detected significant levels of microplastics in composts and other organic amendments, particularly those derived from food wastes and biosolids. These findings suggest that composters may need to pay closer attention to plastic contamination in their feedstocks and take steps to minimise it through improved source separation, screening, and quality control measures.

The paper recommends that AS4454 and other compost standards should be updated over time to reflect the latest scientific evidence on microplastics and other emerging contaminants. This could involve developing standardised testing methods for microplastics, setting appropriate limits based on risk assessments, and providing guidance on best practices for minimising contamination. The paper also emphasises the need for ongoing research to better understand the sources, fate, and impacts of microplastics in composts and soils, and to develop effective strategies for managing them.

More broadly, the AORA paper highlights the need for greater harmonisation and consistency in how compost standards and regulations are applied across different jurisdictions in Australia. Currently, there is significant variation in how AS4454 is referenced and enforced by state and territory regulators, with some requiring mandatory compliance for certain types of facilities or end uses, while others treat it as a purely voluntary standard. This inconsistency can create confusion and additional costs for composters who operate across multiple jurisdictions or who sell their products into different markets.

To address this challenge, the AORA paper suggests that there may be opportunities for greater collaboration and alignment between regulators, industry groups, and standards bodies to promote a more consistent and coherent approach to compost quality management across Australia. This could involve developing national guidelines or protocols for implementing AS4454, harmonising testing and reporting requirements across jurisdictions, and promoting mutual recognition of certification schemes.

Finally, the AORA paper emphasises the ongoing importance of education and engagement with end users and the broader community to build awareness and demand for quality assured compost products. While AS4454 provides a robust framework for ensuring product safety and performance, its value ultimately depends on the willingness of consumers to seek out and purchase certified composts over cheaper, uncertified alternatives.

To build this demand, the paper recommends that the organics recycling industry should continue to invest in research, demonstration projects, and outreach activities that showcase the benefits of compost use for soil health, plant growth, and ecosystem resilience. This could involve collaborating with farmers, landscapers, and other end users to develop tailored products and application guidelines, as well as working with retailers and certifiers to promote the value of AS4454 certification to consumers.

Ultimately, the challenges and opportunities facing AS4454 and the broader organics recycling industry in Australia are complex and multifaceted, requiring a collaborative and adaptive approach from all stakeholders. By working together to continuously improve standards, practices, and market demand, the industry can position itself as a leader in sustainable waste management and a key contributor to a more circular and resilient economy. With the right investments in research, innovation, and engagement, Australia has the potential to become a world leader in compost quality and safety, delivering significant benefits for our soils, our communities, and our planet.

Conclusion

The AORA paper on the comparative analysis of AS4454 and international compost standards provides a timely contribution to the ongoing debate about the future of organics recycling in Australia. The key message is that compost quality standards need to be continually reviewed and updated in light of new scientific evidence, technological advancements, and market expectations.

The evolution of AS4454 will require collaboration from all stakeholders in the industry. It will require investment in new technologies and practices, and a commitment to science and evidence-based decision-making. Key areas for improvement include contaminant management, particularly emerging contaminants like microplastics, and the harmonisation and consistency of compost standards across different jurisdictions.

The success of compost quality standards will depend on their ability to deliver benefits for all stakeholders. Innovative companies like Huum are pushing the boundaries of composting technology and practices to optimise the process and produce high-quality, safe, and consistent products from a wide range of organic waste streams.

Looking to the future, the organics recycling industry in Australia has a vital role to play in the transition to a more sustainable, circular, and resilient economy. By turning organic waste into valuable soil amendments, composts can help regenerate degraded landscapes, support sustainable agriculture, and mitigate the impacts of climate change. The AORA paper provides a starting point for the journey towards a world-class system for compost quality assurance that delivers lasting benefits for our soils, communities, and planet.