Background and context

Kaikōura, New Zealand, faced the challenge of managing biosolids (stabilized sewage sludge) as its resource consent for biosolids stockpiling was set to expire. Community concerns over contaminants and environmental impacts highlighted the need for a sustainable, long-term biosolids management strategy. To address this, local authorities and researchers explored reuse options that would align with environmental and cultural values while ensuring economic feasibility.

Approach

A comprehensive community engagement process was central to the initiative, incorporating hui (meetings), personal interviews, and consultations with Māori representatives and local stakeholders. Biophysical analysis was conducted to assess the composition and safety of biosolids, while cost-benefit and life-cycle analyses evaluated different reuse options. Vermicomposting trials were also introduced to determine improvements in biosolids quality. Key stakeholders included the Kaikōura District Council, the Centre for Integrated Biowaste Research (CIBR), Te Rūnanga o Kaikōura (Māori representatives), and environmental and industry experts. Implementation involved four community hui and 22 key stakeholder interviews to identify values and concerns. Scientific assessments characterized biosolids' nutrient content, pathogens, and contaminants, while economic and environmental impact assessments helped prioritize the best reuse solutions. Community members also participated in voting to select the most suitable biosolids management options.

Outcomes and impacts

The project assessed the reuse potential of 1,500 tonnes of biosolids, with life-cycle analysis confirming that reuse options had lower environmental impacts than landfilling. Economic analysis identified exotic forest application as the most cost-effective solution, with an estimated cost of $46,400. Furthermore, the initiative established a collaborative decision-making model that increased public trust and acceptance in biosolids management. By integrating scientific research into community-driven waste solutions, it demonstrated a balanced approach that aligned environmental, economic, and cultural priorities.

Lessons learned

A community-driven approach was key to gaining broad public support for biosolids reuse. Scientific analysis played a crucial role in addressing safety and contamination concerns, while a multi-option strategy ensured flexibility in biosolids reuse applications. However, challenges included the long-term commitment required for community engagement, the economic feasibility of composting, and regulatory alignment with community perspectives. The Kaikōura model offers a replicable framework for other communities facing biosolids management challenges. Implementing regional biosolids management strategies could further improve efficiency and cost-effectiveness, making it a viable solution for sustainable waste management in similar contexts.