Energy security and decarbonisation of spray drying in New ZealandHeat supply pathways in a gas-constrained market
Andy Wells
Business Development Director
Vulcanic (Spirax Group)
Executive summary
New Zealand’s dairy sector is facing a structural shift in how industrial heat is supplied. Declining natural gas availability, particularly in the North Island, combined with rising prices and increasing uncertainty of long-term supply, is forcing operators of energy-intensive processes such as spray drying to reassess their heat supply strategies.
Spray drying requires the continuous delivery of large volumes of heated air, typically in the range of 180–230°C, with thermal loads often exceeding several megawatts. Historically, natural gas has fulfilled this requirement either through direct-fired air heaters or via high-pressure steam systems used to heat air indirectly.
As gas supply becomes constrained, three principal pathways are emerging:
- Biomass-based systems (typically steam-based in dairy applications)
- Direct electric resistance heating (ERH)
- Electric boiler-based steam systems
Each pathway presents a different balance of cost, complexity, and operational performance.
Biomass systems currently offer the lowest operating cost but require significant capital investment and introduce operational complexity associated with fuel handling, combustion control, and maintenance.
Electric resistance heating provides a fundamentally different approach. By applying heat directly to the air stream, it eliminates intermediate energy conversion steps, resulting in a simple, compact, and highly controllable system. While operating costs are higher under current electricity pricing, ERH offers advantages in process stability, deployment speed, and long-term alignment with New Zealand’s increasingly renewable electricity grid.
Electric boiler systems, which generate steam for indirect air heating, introduce additional complexity and efficiency losses and are generally not well suited to applications where steam is not inherently required.
The selection of an appropriate heat supply pathway is therefore not solely an economic decision. It must consider system complexity, reliability, site constraints, and long-term energy strategy.