Department of Corrections New Zealand has successfully transitioned away from coal heating at Invercargill Prison, replacing its final coal boiler with a modern renewable wood pellet boiler system delivered by Apricus Eco.
The installation marks a major milestone in reducing operational carbon emissions within New Zealand’s public infrastructure sector and demonstrates how locally sourced renewable fuel can replace traditional fossil fuel systems at scale.
Project Overview
The project involved the installation of a 1MW ÖkoFEN pellet boiler system housed within a modular, containerised “Energy Box” design.
The modular approach was selected to provide:
- Increased operational resilience through multiple smaller boiler modules
- Flexible future expansion or relocation options
- Simplified installation and maintenance
- Reduced onsite construction time
Local Renewable Fuel Supply
A key feature of the project is the use of locally produced wood pellet fuel manufactured just 10.4km away by Niagara Sawmilling Company Ltd.
The pellets are produced using recycled wood shavings and sawdust generated through timber processing operations, creating a highly sustainable closed-loop fuel supply chain.
This local sourcing:
- Reduces transport emissions
- Supports regional industry
- Converts waste material into renewable energy
- Improves long-term fuel security
- Environmental Impact
Environmental benefits include:
- 99% reduction in CO₂ emissions
- Approximately 744 tonnes of CO₂ avoided annuall
- Elimination of coal use at the facility
- Increased reliance on renewable New Zealand energy sources
The project demonstrates how biomass energy can provide a practical decarbonisation pathway for large-scale institutional heating applications.
Smart System Operation & Automation
The boiler system includes advanced automation and remote monitoring capabilities designed to improve reliability and reduce maintenance requirements. This connectivity allows operators and installers to remotely manage and adjust the system from virtually anywhere, improving responsiveness and minimising downtime.
Low Maintenance Design
The system was designed for efficient long-term operation with minimal manual intervention.
Ash produced by the boilers is collected in external ash boxes that typically require emptying only once every two weeks. When full, the system automatically displays an “Ash Box Full” warning notification.
The ash by-product is also certified as an organic fertiliser and can be safely reused in gardens and landscaping applications.
Project Outcomes
Feedback from stakeholders including Department of Corrections New Zealand, Downer Group, and Octa Project Management has been overwhelmingly positive regarding both project delivery and operational performance.
The installation is also believed to be the largest ÖkoFEN boiler installation globally, showcasing New Zealand’s capability to deliver world-leading renewable energy infrastructure solutions.
Marcus Baker
Apricus Eco
Victor Ala
Octa Associates - Projected Management for the installation
“Throughout the project, Apricus Eco consistently demonstrated a highly cooperative and professional approach. Their ability to anticipate upcoming activities, constraints, and interfaces enabled effective coordination and supported the achievement of critical project milestones.”
Wayne Harpur
Rayners - Key part of the team of local contractors that delivered this project.
“Projects of this complexity are only possible through strong partnerships, trusted relationships, and a collective commitment to delivering exceptional outcomes.”
