MRF, CDS, e-Waste and Battery Recycling HVAC Duct Guide — Australian Engineering Reference

Why recycling and waste sortation HVAC is not general industrial HVAC

Australian materials recovery and waste sortation is one of the most demanding industrial HVAC environments built outside a regulated cleanroom. A general factory exhaust system handles dust. A recycling facility handles dust plus odour plus bioaerosol plus heavy metal plus deflagration risk plus thermal runaway risk plus the inevitable mixed-feedstock surprise that arrives at the tip face most weeks of the year. The ductwork is not a building service. It is a primary process system. When it fails, the operator either breaches a Workplace Exposure Standard, breaches an EPA licence condition, breaches a fire engineer's deflagration assumption, or closes the line to clean filters that should never have loaded that quickly in the first place.

The 2018 international import restrictions on mixed paper and contaminated plastic from major Asian importers ended the easy economics of Australian kerbside recycling. The federal Recycling Modernisation Fund of roughly AUD 250 million plus matched state funding has driven a steady wave of domestic MRF, plastic recycling, FOGO and battery recycling facility construction since 2020. Through 2026, state EPAs continue raising resource recovery targets, the Container Deposit Scheme rollout continues across Victoria after Queensland, New South Wales, the ACT and Western Australia, and the federal e-waste recovery scheme is reshaping the back-end of consumer electronics. Every one of those facilities needs an HVAC duct system that passes a fire engineer's audit, a Safe Work Australia inspection and a state EPA licensing review on the same drawings.

This guide is the working reference our Box Hill North engineers use when scoping ductwork machinery for Australian recycling and sortation projects. It is written for the mechanical consulting engineer specifying the system, the head contractor pricing the package, the fabricator deciding which SBKJ machine line covers the project mix, and the operator trying to read both the drawings and the tender returns. It is not marketing. Where SBKJ machinery is the right tool, we say so. Where the project needs something outside our scope — primary caustic scrubber bodies, FRP stack sections, fabric filter media — we say so as well.

The Australian recycling and sortation operator landscape in 2026

Anyone specifying HVAC for an Australian recycling facility benefits from understanding who actually operates these plants, because the operator's standard and procurement habits dictate the duct specification more than any code. The 2026 operator landscape is concentrated but not monopolistic, and the technical standards diverge meaningfully across operators.

• Cleanaway Waste Management (ASX:CWY), headquartered in Melbourne, runs over 250 depots and resource recovery sites nationally. Cleanaway operates kerbside MRFs in multiple states, post-collection sortation depots, plastic recycling at Albury and Wetherill Park, a partnership with TOMRA on Container Deposit Scheme infrastructure in New South Wales, and a major liquid waste portfolio. Cleanaway specifies AS 4254.1 and AS 4254.2 construction class as the floor on most projects and asks for AS 1668.2 calculations as part of the tender pack.
• Veolia Australia, headquartered in Sydney, holds more than 350 service contracts including major municipal MRFs, organics processing, hazardous and liquid waste, and the Woodlawn alternative waste treatment facility south of Goulburn. Veolia inherits European group HVAC standards — EN 1505 and EN 1506 are commonly referenced alongside AS 4254 — and is the most rigorous on tipping floor odour management.
• SUEZ Recycling and Recovery Australia, headquartered in Sydney with operations across Western Australia, New South Wales, Victoria and Queensland. Comparable European HVAC heritage to Veolia, with strong process exhaust expertise on FOGO and MSW residual.
• ResourceCo Group, headquartered in Adelaide with a Wetherill Park (NSW) processing line. Strong in alternative fuel from refuse-derived fuel and tyre processing. Typically specifies welded heavy-gauge construction on shredder hood extract because the dust load is high.
• Bingo Industries, now private under CPE Capital, headquartered in Sydney with 21 facilities across New South Wales, Victoria and Queensland. Strong on construction and demolition waste recovery, where silica and concrete dust dominate the contaminant register.
• Re.Group, headquartered in New South Wales and operating MRFs across multiple Australian states, is one of the larger independent MRF operators with a strong focus on the kerbside single-stream and dual-stream recovery rate.
• Visy recycles paper and cardboard at scale across Australian east coast facilities, with associated MRF operations. The paper recovery process is dust- and combustion-sensitive, and Visy facilities typically run heavy-gauge baghouse capture with explosion-vented collectors.
• Sims Metal Management (ASX:SGM), headquartered in Sydney with yards across Australia, is the dominant ferrous and non-ferrous metal recycler. Heavy on shredder hood extract, with eddy current and dense-media separation tied into the duct package.
• Owen International and TES (Total Environmental Solutions), Sydney-based e-waste and battery processors, run the highest-risk thermal runaway extract paths in the Australian recycling sector. Both operate under NFPA 855 alignment with AS/NZS 5139 reference.
• Envirostream Australia at Lithgow (NSW) and Campbellfield (VIC), Renewable Metals, Lithium Australia and several smaller battery recyclers operate dedicated lithium-ion shred and hydrometallurgical lines. The HVAC duct package on these facilities is the heaviest of any sortation operation.
• Pact Group recycling division operates PET reprocessing facilities; the wash and extrusion line is dust-light but VOC-bearing, with dedicated extract to thermal oxidiser or carbon polish.
• Repurpose It at Epping (VIC) handles concrete and construction waste — silica-dominated, with respirable crystalline silica as the lead WES driver.
• Council MRFs across the City of Melbourne, City of Sydney, Brisbane City Council, Wollongong and others operate variously in-house or under contract. Local government specifications tend to mirror the relevant state EPA approval template rather than carry an independent technical standard.
• Container Deposit Scheme operators — TOMRA Cleanaway JV in New South Wales, Container Exchange in Queensland, Return-It in Western Australia, Marine Rescue NSW and the VicReturn scheme currently under design — operate auto-sortation depots that are dust-light but volume-heavy. The HVAC duct package is general extract plus minimal dust capture, but the boundary air quality and noise requirements are tight because the depots are typically in commercial zoning adjacent to residential.
• Pyrolysis and gasification waste-to-energy plants — currently small in Australia but growing — operate high-temperature stack ductwork that sits closer to a chemical plant than a recycling facility in design terms.

The pattern across operators is clear: the larger and more multinational the operator, the tighter the HVAC duct specification and the more rigorous the tender return. The smaller and more local the operator, the more the consulting engineer's preference drives the standard. SBKJ has supplied auto duct line and stitchwelder machinery to Australian fabricators servicing facilities across all of these operators, and the dominant requirement is to deliver galvanised G90 work to AS 4254 with the capability to switch to 304L and 316L stainless for the scrubber, CRT, mercury and battery shred sections without changing shops.

The seven-zone HVAC duct map of a recycling facility

Every recycling and sortation facility decomposes into seven HVAC zones, regardless of feedstock, scale or operator. Getting the zone map right at concept design saves the project months of rework at detail design.

1. Tipping floor — receival zone where trucks discharge feed. Dust load is moderate but highly variable; odour load is dominant on MSW, FOGO and contaminated streams; bioaerosol load is present on FOGO and organics. Held at negative pressure relative to the boundary.
2. Sortation hall — conveyor lines, manual pickers, optical sorters, eddy current and magnetic separators, ballistic separators, trommel screens, air classifiers. Dust load is the dominant contaminant; bioaerosol on trommels; noise and air movement around picker stations is a design constraint.
3. Shredding hall — primary shredders, secondary shredders, granulators. Dust load is heavy and the deflagration risk is the operative HVAC design driver. Spark-resistant construction and explosion venting are mandatory.
4. Specialist process rooms — CRT breakage, mercury lamp recycling, battery shred, hydrometallurgical processing. Each is held at strong negative pressure relative to adjacent zones, with HEPA recovery and recirculation and dedicated scrubber discharge.
5. Bale and bulk storage — densified output, in-process stockpile, paper bales, plastic bales. Fire load dominant, dust load low. Storage tunnel zone classification per AS/NZS 60079 may apply where paper bale CO and methane evolution is credible.
6. Outbound load-out — bale transfer to truck, container loading, refuse-derived fuel discharge. Dust load is moderate, capture is needed at point sources, boundary discharge management dominates.
7. Plant utilities — control rooms, amenities, maintenance workshop, switchroom. Positive-pressure clean supply, isolated from the process exhaust, with HEPA recovery and overpressure protection where it abuts the high-risk specialist process rooms.

The zone boundaries drive the pressure cascade, the duct routing, the material selection at the boundary, and the smoke and fire damper schedule. The pressure cascade rule is: clean-to-dirty flow, never the reverse, with positive pressure on the clean side and progressively deeper negative pressure as the feedstock becomes more contaminated. The cascade is enforced by VAV box modulation on supply and return with offset air determined by the differential pressure controllers on each room, verified during commissioning under both static and worst-case door-open conditions.

Tipping floor extract under AS 1668.2 process exhaust

AS 1668.2 is the Australian process and mechanical ventilation standard and the operative code for every recycling facility tipping floor. It does not prescribe a single air change rate. It frames the requirement as the volume of air required to dilute or capture the contaminant load to below the Workplace Exposure Standard or the relevant boundary air-quality limit. The calculation runs forward from the contaminant generation rate — established by emission factors for the waste stream — to the ventilation rate required to hold the concentration below the limit at the receptor of concern.

In practice, Australian MRF tipping floors run between 6 and 10 air changes per hour of general ventilation when sized to AS 1668.2 with localised capture overlaid at the tip face. The floor is held under negative pressure relative to the boundary and the surrounding amenities. The pressure differential is typically 12 to 25 Pa, maintained by fast roll-up doors at every truck entry and exit and by the VAV control on the supply and extract fans. When the door is open the differential collapses temporarily; the design must demonstrate that the cumulative open-door time and the boundary discharge concentration during open-door scenarios still meet the AS 3580 receptor target and the relevant state EPA licence condition.

The contaminants of concern on a kerbside MRF tipping floor:

• Total suspended particulate — heavy under high-throughput receival, dominated by paper fibre dust and shredded plastic fines. WES is not the operative limit; AS 3580 boundary monitoring and visual nuisance to the residential receptor is.
• Respirable crystalline silica at WES 0.05 mg per cubic metre, driven by any glass and demolition fines in the kerbside stream. The 2020 reduction from 0.1 to 0.05 mg/m3 tightened the calculation considerably and forced upgrades on several Australian MRF tipping floor extracts.
• Bioaerosol — viable bacteria, fungal spores and endotoxin, dominant on FOGO and any MSW with putrescible fraction. There is no formal WES, but Safe Work Australia and state work health and safety regulators expect a documented capture and treatment regime.
• Volatile organic compounds and hydrogen sulphide — odour drivers, dominant on putrescible and anaerobic streams. The receptor is the residential boundary and the operative limit is the AS 3580 monitoring threshold backed by the state EPA licence.
• Methane — credible on FOGO and any tipping floor with extended residence time, with AS/NZS 60079 hazardous area implications where the concentration approaches the lower flammable limit.

The extract duct main from the tipping floor is typically galvanised G90 (Z275) rectangular construction to AS 4254.2 medium-pressure class for routing inside the building, transitioning to 316L stainless or polyethylene-lined steel for the section between the building exit and the odour treatment plant where the gas stream becomes humid and acidic-condensing. The duct velocity is 12 to 16 m per second to keep particulate entrained without excessive pressure drop. The fan is a backward-curved centrifugal with corrosion-resistant impeller coating, sized for the worst-case open-door makeup demand plus 15 percent margin.

Sortation hall — conveyors, optical sortation, separators, classifiers, trommels

The sortation hall is where the recycling facility splits the feedstock into sale-grade streams. Each piece of equipment has a distinct HVAC duct demand. Getting the equipment-by-equipment specification right at concept design saves the project from the all-too-common pattern of generic ducted hood capture that fails to meet capture velocity at the camera face on commissioning.

Optical sortation NIR camera line

Near-infrared optical sortation is the heart of a modern MRF. A typical 60 tonne per hour mixed container line runs four to twelve NIR camera banks with air-knife ejector arrays, sorting PET clear, PET coloured, HDPE natural, HDPE coloured, PP and other resin and colour fractions. The NIR cameras are dust-sensitive. A dusty camera face misreads polymer signatures, drops the sort accuracy, and forces a shutdown for manual cleaning. The HVAC response is dust suppression upstream by enclosed conveyor hoods and a localised extract above each camera bank at 0.3 to 0.5 m per second face velocity. The air-knife ejector blast itself is high-volume low-velocity downstream and does not require capture, but the discharge chute below the air-knife — where the ejected fraction lands — does benefit from a dust hood at 0.5 to 0.8 m per second capture velocity. The total extract volume for a typical 60 tonne per hour MRF optical line is 8,000 to 14,000 cubic metres per hour, routed to a baghouse with PTFE membrane filter media. Duct material is galvanised G90 with stitchwelded longitudinal seams to AS 4254.2 medium-pressure class.

Eddy current separator

Eddy current separators recover non-ferrous metal — predominantly aluminium beverage cans from the kerbside stream and aluminium foil and copper wire from e-waste. The separator is enclosed and the dust load at the separator itself is minimal. The relevant HVAC duct demand is the conveyor transfer upstream and downstream — point-source dust capture at 0.5 m per second face velocity. Typical extract volume per separator is 600 to 1,200 cubic metres per hour. Galvanised G90 to AS 4254.1 is sufficient.

Magnetic ferrous separator

Overband or pulley magnets recover ferrous metal — steel beverage cans from kerbside, steel-shelled batteries from e-waste, mixed ferrous from C&D. Dust load at the magnet is minimal. Conveyor transfer capture upstream and downstream is the same 0.5 m per second point-source extract as the eddy current separator. Galvanised G90 to AS 4254.1.

Air classifier and windsifter

Air classifiers separate light and heavy fractions using a high-velocity air stream. The light fraction — film plastic, paper, foam — is carried out the top of the classifier; the heavy fraction — glass, rigid plastic, metal — falls through the bottom. The classifier extract is the dominant duct flow on the machine: 6,000 to 18,000 cubic metres per hour at high transport velocity (18 to 22 m per second) into a baghouse for the light fraction recovery. The duct between the classifier and the baghouse is heavy-gauge galvanised G90 or 304L stainless on long runs, stitchwelded longitudinal seams, AS 4254.2 medium-pressure class. The baghouse runs PTFE membrane filter media with NFPA 68 explosion vent panels and NFPA 69 isolation on the inlet.

Trommel screen

The trommel is a rotating drum screen that separates oversize from undersize feedstock. On FOGO and MSW the trommel is the dominant bioaerosol generator in the facility. The screen is enclosed under negative pressure of 25 to 50 Pa, extract is taken at 4 to 6 m per second capture velocity, and the discharge is routed to a biofilter or chemical scrubber depending on the contaminant profile. The extract duct between the trommel and the biofilter is 316L stainless steel because compost off-gas is humid, organic-acid-laden and condensing; galvanised corrodes within months in this service. Where the trommel handles dry kerbside recyclate the bioaerosol load is lower and galvanised G90 with stitchwelded seams is sufficient.

Ballistic separator

Ballistic separators tilt and oscillate paddles to split flats from rounds — paper from containers in single-stream MRF. Dust load is similar to a conveyor transfer. Point-source capture at 0.5 m per second face velocity, galvanised G90 to AS 4254.1.

Shredding hall — the deflagration risk that drives the duct design

Shredders are the highest-risk HVAC zone in a recycling facility. Every shredder generates a fine combustible dust cloud. Paper fibre dust falls under NFPA 660 (the consolidated combustible dust standard from 2025 onwards, formerly NFPA 484 for metals and NFPA 654 for general particulate) typically as St-1 with Kst values in the 50 to 200 bar.m per second range. Shredded plastic dust is similar. Wood dust from C&D processing is more aggressive — Kst commonly above 200 bar.m per second, placing it at the upper end of St-1 or into St-2. Refuse-derived fuel shred is heterogeneous and assumed worst-case unless tested.

The HVAC duct response is layered. Local capture at the shredder hood — at 1.5 to 2.5 m per second face velocity around the discharge throat — collects the airborne dust before it escapes the room. The capture duct routes through heavy-gauge galvanised G90 construction, stitchwelded longitudinal seams, AS 4254.2 medium-pressure class, to an explosion-vented baghouse. The baghouse is fitted with NFPA 68 vent panels sized for collector volume and Kst, discharging through a flame arrestor and a duct path of welded heavy-gauge construction to a safe outdoor location at least 6 metres clear of any building opening and 15 metres clear of any combustible storage. NFPA 69 isolation on the inlet — rotary airlock or chemical suppression — breaks the propagation path back to the shredder. The fan is specified as spark-resistant per AMCA Type A or B with aluminium or aluminium-bronze impeller, and the fan motor is rated to the AS/NZS 60079 zone classification of the duct interior.

Where the shredder handles refuse-derived fuel or e-waste with credible lithium-ion contamination, the deflagration response is augmented with continuous hydrogen and hydrogen-fluoride gas detection at the hood interlocked to fast-acting isolation dampers, a nitrogen or argon inert gas knock-down plumbed into the shredder enclosure, and a process trip on the shredder drive. The shredder pre-vent extract path between the hood and the explosion-isolated baghouse is the most critical duct on the project — a wrongly-specified gauge, an incomplete weld or a missing reinforcement collapses under the pressure pulse and propagates the deflagration into the building.

SBKJ recommends a stitchwelder for the shredder pre-vent extract path because the welded longitudinal seam is mandatory under NFPA 660. The SBKJ SBSF-1525 stitchwelder operates at 2.5 kW and produces continuous welded seams on heavy-gauge galvanised or 304L stainless for the heavy-gauge construction class typical of deflagration-rated ductwork. The SBFB-1500 folder (7.5 kW, 1.20 m per minute) covers the heavy-gauge folded sections required around access doors, transitions and bracketry.

Container Deposit Scheme depots — dust-light, volume-heavy, boundary-tight

Container Deposit Scheme auto-sortation depots are the newest entry in the Australian recycling landscape and the most operationally distinct from a kerbside MRF. The feedstock is consumer-returned single-use beverage containers — aluminium cans, PET bottles, HDPE bottles, glass — typically empty and rinsed. The dust load is therefore minimal. The volume is heavy because the consumer foot traffic and the truck arrival pattern is high. The boundary is tight because the depots are commercial-zoning facilities, often adjacent to residential.

The HVAC duct demand is dominated by general ventilation to AS 1668.2 with localised capture only at the auto-sortation reverse-vending machine discharge and at any baler or compactor. General ventilation is typically 3 to 5 ACH on the main sortation floor, with a stronger differential pressure to atmosphere — 25 Pa or more — to manage odour from any residual organic content in the returned containers. The duct material is galvanised G90 throughout to AS 4254.1, slip-flange construction, EPDM gasketing. The fans are general-purpose backward-curved centrifugal with standard motor enclosure. There is no deflagration risk and no heavy metal capture demand.

The HVAC duct package on a Container Deposit Scheme depot is small relative to a kerbside MRF — typically AUD 200,000 to AUD 500,000 of installed ductwork against a kerbside MRF's AUD 2 to 5 million. The SBKJ machinery suitability is clear: a single SBAL-V auto duct line covers the entire project, with SBTF-1500C for the round return-air sections. The economics work for a fabricator running multiple Container Deposit Scheme depot projects in parallel — TOMRA Cleanaway in New South Wales, Container Exchange in Queensland, Return-It in Western Australia, the VicReturn scheme currently in design.

e-Waste shredder line — heavy metal, lithium-ion, mixed feedstock

e-Waste recycling is the highest-risk recycling operation in Australia other than dedicated lithium-ion battery recycling. The feedstock under the federal National Television and Computer Recycling Scheme and the state e-waste recovery schemes is a heterogeneous mixture of cathode ray tube monitors and televisions (lead-bearing funnel glass and phosphor), flat-panel displays (mercury backlights pre-2012 stock), printed circuit boards (lead solder, beryllium copper, brominated flame retardants), consumer batteries (lithium-ion, nickel-metal hydride, alkaline, lithium primary), capacitors (PCB-contaminated stock occasionally still found), and bulk plastic and metal casing.

The HVAC duct demand is the highest-specification capture in the recycling sector outside dedicated battery shredding. The shredder hood is enclosed and capture is taken at 2.0 to 2.5 m per second face velocity. The duct routes through 304L stainless steel construction with welded longitudinal seams, stitchwelded transverse joints, AS 4254.2 medium-pressure class with NFPA 660 deflagration reinforcement. The baghouse is fitted with HEPA H13 polish stage on the clean side because the dust contains lead, cadmium, beryllium and mercury at concentrations that exceed Safe Work Australia WES many times over at the source. The baghouse-to-stack run is 304L stainless throughout. The fan is spark-resistant with aluminium impeller and the fan motor is rated to AS/NZS 60079 Zone 2 because the lithium-ion ignition risk is credible despite the inerting attempts upstream.

The heavy metal dust caught in the baghouse and the HEPA stage is regulated waste under AS 5061 and AS 5062 classification — typically a Category 4 or 5 hazardous waste depending on lead and cadmium content — and must be sealed and transferred to a licensed recovery facility. The duct cleaning regime under operational AS 1851 inspection is monthly internal inspection with quarterly HEPA bag-out replacement, and personal monitoring of operators against Safe Work Australia WES for lead (0.05 mg/m3), cadmium (0.01 mg/m3), mercury (0.025 mg/m3 vapour) and beryllium (0.0002 mg/m3) is the operative compliance regime.

Cathode ray tube breakage room — Pb dust HEPA H13/H14 capture

CRT recycling is winding down in Australia as the legacy stock is processed out, but several operators — Owen International, Recycle Smart and the larger Cleanaway and Sims e-waste lines — still run dedicated CRT breakage rooms. The room is held at strong negative pressure of 15 to 25 Pa relative to surrounding zones, with airlock door pairs and pressure differential controllers in the BMS. The feed CRT monitors and televisions are broken inside the room by a controlled crushing operation that separates the leaded funnel glass from the panel glass, electron gun and shadow mask.

The dust load is fine, lead-bearing and toxic. The duct extract is at 18 to 22 m per second transport velocity to keep the dust entrained — too low and the dust drops out and accumulates as a Safe Work Australia inhalation risk during maintenance. The duct material is 304L stainless steel with welded longitudinal seams for ease of decontamination at end-of-life. The room extract routes through a baghouse with HEPA H13 or H14 final filtration, and the HEPA discharge runs to a 304L stainless stack with continuous particulate monitoring against the state EPA licence boundary limit.

Operator personal monitoring is mandatory: lead WES at 0.05 mg/m3 is the operative compliance limit, and the duct capture must hold the breathing-zone concentration comfortably below this. Operators are typically in respiratory protective equipment as a final defence, but the primary protection is the HVAC duct capture.

Mercury lamp recycling — Hg vapour scrubber and activated carbon polish

Fluorescent lamp recycling — both compact fluorescent and linear tube — is operated by a small number of Australian processors including the larger Cleanaway and Veolia e-waste sites. Each lamp contains 2 to 50 mg of mercury depending on type and vintage. The recycling process breaks the lamp inside an enclosed crushing chamber, separates the glass, end caps and phosphor, and routes the released mercury vapour through a dedicated capture train.

The HVAC duct response is a 304L stainless extract path from the crusher to an activated carbon scrubber with sulphur-impregnated carbon (the sulphur reacts with the mercury vapour to form mercuric sulphide and trap it). The extract velocity is 12 to 16 m per second. The room is held at negative pressure of 12 to 25 Pa. The carbon discharge runs to a 304L stainless stack with continuous mercury vapour monitoring against the Safe Work Australia WES of 0.025 mg/m3 and the NEPM Air Toxics ambient air quality measure at the residential receptor. The spent carbon is regulated waste under AS 5061 and is recovered for licensed mercury recycling.

Lithium-ion battery shredder — the highest-stakes HVAC duct path in recycling

Lithium-ion battery recycling is the fastest-growing recycling segment in Australia and the most demanding HVAC duct application in the sector. Envirostream Australia at Lithgow and Campbellfield, Renewable Metals, Lithium Australia and a handful of smaller operators run dedicated lithium-ion shred lines that process EV battery packs, consumer cells, e-bike batteries and grid storage cells. The recycling process discharges the cell to a safe state of charge, shreds the cell mechanically inside an inerted enclosure, separates the black mass from the casing and current collectors, and routes the black mass for hydrometallurgical processing.

The thermal runaway risk is real and the gas hazard is severe. A single cell entering thermal runaway releases hydrogen, methane, carbon monoxide, hydrogen fluoride, hydrogen bromide and phosphoryl fluoride (PF5) into the extract duct at temperatures up to 700 degrees C. Hydrogen fluoride is the lead hazard at WES 3 ppm short-term exposure limit — exposure above this can cause acute pulmonary injury. The HVAC duct response layers four controls aligned to NFPA 855 and AS/NZS 5139:

• Inerted enclosure. The shredder operates under continuous nitrogen or argon blanket with oxygen concentration held below 4 percent. The extract duct from the enclosure carries the inert gas plus the entrained dust load, and the makeup gas is metered against extract flow.
• Explosion vent and isolation. NFPA 68 vent panels on the shredder enclosure and the downstream baghouse, sized for the worst-case deflagration pressure pulse. NFPA 69 isolation by chemical suppression or fast-acting valve on the inlet duct breaks propagation back to the process. The duct construction between the enclosure and the baghouse is welded heavy-gauge 304L stainless to AS 4254.2 with reinforcement against the design pressure pulse.
• Three-stage scrubber train. Caustic primary for HF and HCl knock-down (typically 5 to 8 percent sodium hydroxide solution), acid secondary for ammonia and amine capture (typically 5 percent sulphuric acid solution), and activated carbon polish for organic carbonates. The primary scrubber body is normally FRP (outside SBKJ scope). The interstage ducts are 316L stainless because chloride concentration from caustic carryover demands the higher molybdenum content. The carbon polish-to-stack run is 304L stainless. The stack discharge is 304L stainless with a continuous emissions monitor for HF, HBr, HCl and total VOC against Safe Work Australia WES and NEPM Air Toxics ambient receptors.
• Continuous gas detection and process interlock. Hydrogen, hydrogen fluoride, hydrogen bromide, hydrogen chloride, carbon monoxide and oxygen sensors at the enclosure interlocked to fast-acting isolation dampers, inert gas knock-down (additional argon or carbon dioxide injection), and a process trip on the shredder drive. The detection logic is fail-safe: any sensor fault closes the dampers and trips the drive.

SBKJ supplies the duct fabrication machinery for the extract path from the shredder through to the stack. The SBAL-V auto duct line in 304L stainless configuration covers the rectangular main runs. The SBSF-1525 stitchwelder produces the welded longitudinal seams mandatory under NFPA 660 and NFPA 855 for the deflagration-rated extract sections. The SBTF-1602 spiral tubeformer produces the round transition sections between rectangular main and the scrubber inlet. The primary caustic scrubber body itself is outside SBKJ scope and is supplied by FRP specialist fabricators — SBKJ provides the duct interfaces in 304L on the inlet side and 316L on the outlet side. The SBLR-600A roll bender (7.6 m per minute) covers the radius transitions on stack tie-ins. The total duct fabrication for a typical 5,000 tonne per annum lithium-ion battery shred line is 2,500 to 4,000 m2 of duct, fabricated in 3 to 5 shifts on an SBAL-V running double shift.

Plastic flake wash line — water mist extract

Plastic recycling — Pact Group PET reprocessing, Cleanaway plastic recycling at Albury, multiple smaller HDPE and PP recyclers — runs a plastic flake wash line as the central process. Baled plastic is sorted, ground to flake, washed in caustic water, rinsed in fresh water, dried in a centrifugal dewatering stage, and either extruded back to pellet or shipped as washed flake.

The wash line is humid and the dominant extract demand is water mist capture above the wash tanks and the rinse tanks. The extract is at 1.0 to 1.5 m per second face velocity, sufficient to draw the mist into the duct without entraining excessive splash. The duct material is 316L stainless steel for the wash tank extract because caustic carryover is corrosive to galvanised within months; 304L stainless suffices for the rinse tank extract. The mist is condensed in a knockout drum before any fan and discharged to the wastewater treatment system.

The extruder section is dry but VOC-bearing. The polymer melt at 200 to 280 degrees C off-gases residual additives and oligomers. The extruder vent is captured at the die face at 0.5 to 1.0 m per second face velocity and routed to a thermal oxidiser or activated carbon polish before stack discharge. The duct between the extruder and the thermal oxidiser is 304L stainless because the gas stream is mildly acidic-condensing. The post-oxidiser stack is galvanised G90 because the gas has been cleaned.

Compost and FOGO biofilter return — humidity, organic acid, bioaerosol

FOGO (food organics and garden organics) processing has expanded rapidly in Victoria, New South Wales and Western Australia under the relevant state government source separation programs. Repurpose It at Epping, Veolia's Woodlawn AWT, SUEZ's organics facilities and several council-run compost operations process FOGO at scales from a few thousand tonnes per annum to over 100,000 tonnes per annum.

The HVAC duct demand on a compost facility is dominated by odour and bioaerosol management. The receival floor, the windrow turning hall (where applicable), the trommel screen and the maturation hall all generate dimethyl sulphide, ammonia, hydrogen sulphide and a long tail of organic VOC at concentrations that breach the AS 3580 residential receptor target without treatment. The HVAC response is a biofilter scrubber train — primary chemical or biofilter, polishing activated carbon, stack discharge.

The compost biofilter is typically open-bed wood-chip or bark over a perforated plenum, with residence time of 30 to 45 seconds, irrigated to 50 to 65 percent moisture content. Some operators run an enclosed biofilter with stack discharge instead, which gives more dispersion margin against the residential boundary at the cost of higher fan power. The extract duct between the process and the biofilter is 316L stainless steel because compost off-gas is humid, organic-acid-laden and condensing — galvanised corrodes within months. The biofilter-to-stack return duct (where the biofilter is enclosed) is 316L stainless. Open-bed biofilters discharge directly to atmosphere; enclosed biofilters with a stack are sized against AS 3580 receptors and the residential boundary.

Paper bale storage — fire load and CO/methane evolution

Paper recycling at scale — Visy across the Australian east coast, Cleanaway's mixed paper streams, the larger council MRFs — accumulates baled mixed paper in storage tunnels for road or rail dispatch to the paper mill. Paper bale storage is the leading fire risk in the recycling sector. Bales self-heat by microbial action and by chemical oxidation of residual moisture and contaminants, and an internal hot-spot can smoulder for days before breaking through to flaming combustion. The fire load is enormous — a typical paper bale storage tunnel holds 5,000 to 20,000 tonnes of paper, equivalent to 100 to 400 GJ of stored fuel energy per metre of tunnel length.

The HVAC duct demand on the paper bale storage tunnel is general ventilation at 4 to 6 ACH plus continuous CO and methane gas detection. CO is the leading indicator of bale self-heating — a CO concentration above 25 ppm at the tunnel exhaust indicates active microbial decomposition and triggers a tunnel inspection regime. Methane evolution is credible where the bale moisture content is high, with AS/NZS 60079 hazardous area implications if the concentration approaches the lower flammable limit (5 percent). The ventilation duct material is galvanised G90 throughout to AS 4254.1. The fan is general-purpose backward-curved centrifugal with standard motor enclosure. The fire protection system is independent — typically deluge or in-rack sprinkler under AS 2118 — but the HVAC must not propagate fire between tunnels, so fire dampers per AS 1668.1 and AS 1530.4 are mandatory at every fire-rated wall penetration.

Refuse-derived fuel shredder — the highest fire risk in residual sortation

Refuse-derived fuel (RDF) processing — ResourceCo, Cleanaway, and several emerging operators — shreds residual waste after recyclables recovery to produce a fuel pellet or fluff for cement kiln or waste-to-energy combustion. The feedstock is heterogeneous and the fire risk is the highest of any non-battery recycling operation. The HVAC duct response combines the deflagration controls of any shredder with the heavy general ventilation of a mixed-waste hall: 10 to 15 ACH on the shredder hall, heavy-gauge stitchwelded galvanised G90 extract from the hood to an explosion-vented baghouse, spark-resistant fans, NFPA 660 alignment throughout, and continuous gas detection for CO and methane.

The dust load is high and the extract baghouse is the largest single duct termination on the project. Typical extract volume on a 100,000 tonne per annum RDF line is 60,000 to 120,000 cubic metres per hour. The duct main between the shredder hall and the baghouse is rectangular 600 mm by 800 mm or 800 mm by 1000 mm depending on flow, in heavy-gauge galvanised G90 with stitchwelded longitudinal seams to AS 4254.2. The SBKJ machinery fit is the SBAL-V auto duct line with the SBSF-1525 stitchwelder running parallel.

Glass cullet handling — silica dust and the WES 0.05 mg/m3 challenge

Glass recycling produces cullet for re-melt in container glass furnaces. The cullet handling chain — receival, crushing, washing, sizing, optical sortation by colour — generates respirable crystalline silica dust at concentrations that exceed the Safe Work Australia WES of 0.05 mg/m3 many times over at the source. The HVAC duct demand is local capture at every transfer point at 0.5 to 1.0 m per second face velocity, with the extract routed to a baghouse with HEPA H13 polish stage on the clean side. The duct material is galvanised G90 throughout to AS 4254.2, with stitchwelded longitudinal seams on the heavy-gauge transport sections. The fan is general centrifugal with corrosion-resistant impeller.

The silica dust caught in the baghouse is general industrial waste under AS 5061 — it is not regulated waste, but the disposal route is typically licensed landfill or, increasingly, beneficial reuse as construction fill. The duct cleaning regime is monthly internal inspection with quarterly bag replacement, and personal monitoring of operators against the 0.05 mg/m3 WES is mandatory.

Pyrolysis and gasification waste-to-energy stack

Pyrolysis and gasification waste-to-energy plants — currently small in Australia but growing under federal and state alternative fuel and energy-from-waste programs — operate high-temperature stack ductwork that sits closer to a chemical plant than a recycling facility in design terms. The pyrolysis reactor operates at 400 to 700 degrees C in an oxygen-starved atmosphere, producing a syngas, a char and a tar. The gasification reactor operates at 700 to 1200 degrees C with controlled air or oxygen feed, producing a higher-quality syngas. Both technologies route the gas through a quench, a gas cleaning train (cyclone, scrubber, dust filter), and either a syngas engine for power generation or a thermal oxidiser for direct disposal.

The HVAC duct demand is high-temperature alloy on the reactor outlet (typically AISI 309 or 310 stainless for service to 1000 degrees C), 316L stainless on the post-quench gas cleaning train, and galvanised G90 on the post-cleanup syngas distribution to the engine. The stack discharge is monitored continuously for CO, NOx, SO2, HCl and total VOC against the state EPA licence and NEPM Air Toxics ambient receptors. SBKJ machinery suitability is limited on the high-temperature reactor outlet — that work goes to specialist pressure-vessel fabricators — but the SBAL-V in 304L and 316L configuration covers the gas cleaning train and the post-cleanup distribution. The SBSF-1525 stitchwelder produces the welded seams required on the high-pressure sections.

Materials selection by zone

Material selection across the recycling and sortation duct package is more nuanced than in general HVAC, and getting it wrong is expensive — both as a direct cost and through accelerated failure of mis-specified runs.

• General tipping floor and sortation hall extract: Galvanised G90 (Z275) coating per ASTM A653 or AS 1397, rectangular to AS 4254.1 or AS 4254.2 depending on pressure class. The default for around 70 percent of the project tonnage.
• Boundary section between tipping floor and odour treatment plant: 316L stainless or polyethylene-lined steel where the gas stream becomes humid and acidic-condensing. Galvanised corrodes within 12 to 24 months in this service.
• CRT breakage room extract: 304L stainless with welded longitudinal seams for ease of decontamination at end-of-life. Lead dust capture demands HEPA H13 or H14 final filtration.
• Mercury lamp extract: 304L stainless throughout from the crusher to the carbon scrubber and beyond to the stack.
• e-Waste shredder extract: 304L stainless from the shredder hood to the baghouse, with welded longitudinal seams and stitchwelded transverse joints. NFPA 660 deflagration reinforcement throughout.
• Lithium-ion battery shredder extract: Welded heavy-gauge 304L stainless from the enclosure to the baghouse. 316L stainless on the scrubber interstage runs because of chloride carryover. 304L on the post-carbon polish-to-stack. FRP on the primary caustic scrubber body itself (outside SBKJ scope).
• Compost and FOGO biofilter return: 316L stainless because the gas stream is humid, organic-acid-laden and condensing. Open-bed biofilter discharge directly to atmosphere; enclosed biofilter return through 316L stainless duct to a 316L stainless stack.
• Plastic flake wash extract: 316L stainless on the caustic-bearing wash tank extract; 304L stainless on the fresh-water rinse tank extract.
• Plastic extruder vent: 304L stainless to the thermal oxidiser or carbon polish; galvanised G90 post-cleanup.
• Shredder pre-vent extract (general): Heavy-gauge galvanised G90 or 304L stainless with stitchwelded longitudinal seams. NFPA 660 deflagration reinforcement.
• Pyrolysis or gasification reactor outlet: AISI 309 or 310 high-temperature stainless. Out of normal SBKJ scope.
• Gas cleaning train post-quench: 316L stainless from quench to dust filter to scrubber. 304L stainless post-scrubber to syngas engine.
• Container Deposit Scheme depot general extract: Galvanised G90 throughout to AS 4254.1.
• Refuse-derived fuel shredder extract: Heavy-gauge galvanised G90 with stitchwelded seams; spark-resistant fan blade.
• Glass cullet handling extract: Galvanised G90 throughout to AS 4254.2; baghouse with HEPA H13 polish.
• Paper bale storage ventilation: Galvanised G90 to AS 4254.1; CO and methane gas detection; fire damper per AS 1668.1 and AS 1530.4.
• Stack and chimney discharge: 304L stainless or 316L stainless depending on gas chemistry; never galvanised because of solar and discharge thermal cycling.

For a deeper comparison of the material trade-offs and where each grade is appropriate, see our reference on galvanised vs stainless steel duct selection.

AS 4254 construction class by service

AS 4254 is the Australian ductwork construction standard, split between AS 4254.1 (flexible duct and acoustic duct) and AS 4254.2 (rigid duct). The relevant pressure class for most recycling facility ductwork is medium-pressure AS 4254.2, with structural reinforcement on long collector inlet ducts under negative pressure and stitchwelded heavy-gauge construction on shredder pre-vent runs.

• AS 4254.1 (low pressure, up to 500 Pa): General supply to control rooms, amenities and clean-supply zones. Slip-flange or TDF flange construction with EPDM gasket. Galvanised G90 in most cases.
• AS 4254.2 medium pressure (500 to 1500 Pa): General extract from tipping floor, sortation hall, conveyor capture, optical sortation extract, trommel extract, eddy current and magnetic separator capture, baler and compactor extract. Slip-flange or TDF flange. Galvanised G90 default; 304L or 316L on the wet and acidic-condensing runs.
• AS 4254.2 high-pressure / negative-pressure (above 1500 Pa): Shredder pre-vent, air classifier extract, baghouse inlet, scrubber interstage, lithium-ion battery enclosure extract. Stitchwelded longitudinal seams. TDF flange with PTFE gasket on chemical service. NFPA 660 deflagration reinforcement on combustible dust service.

The construction class drives the gauge schedule, the flange specification, the reinforcement spacing and the joint sealing. A consulting engineer specifying ductwork for a recycling facility should mark every duct run on the drawing with the AS 4254 class and the gauge schedule, leaving no ambiguity for the fabricator at the take-off.

Fire-rated penetrations and damper maintenance

Every wall, floor and ceiling penetration where the duct crosses a fire-rated barrier requires AS 1530.4 tested and certified seal. The seal system is normally specified by the fire engineer on the project drawings — typical solutions include intumescent collar, mortar fill, proprietary firestop system, or fire-rated duct wrap on the duct itself. The seal is detailed at every penetration, with the certification number recorded on the project compliance schedule.

Fire dampers are required at every penetration of a fire-rated barrier on a duct that does not have an equivalent fire-rated duct construction. The damper specification is to AS 1682, with the operational regime under AS 1851 — drop test on a 12-month cycle, with the test record kept in the operations file. The damper actuator is either a fusible link (typically 74 degrees C for general HVAC, 100 degrees C or higher for process exhaust where the operating temperature is elevated), an electric actuator wired into the BMS, or a pneumatic actuator with a fail-closed configuration.

On battery recycling and lithium-ion shred lines, the fire damper schedule is augmented with fast-acting isolation dampers on the extract path — typically pneumatic-actuated with sub-second response time, interlocked to the gas detection and process trip. These are not AS 1682 fire dampers; they are process safety dampers under AS/NZS 60079 zone classification, and the maintenance regime is monthly functional test with annual full overhaul.

Safe Work Australia Workplace Exposure Standards in the duct design

The duct design is bounded by Safe Work Australia Workplace Exposure Standards at the breathing zone. The operative values for recycling and sortation:

• Respirable crystalline silica: 0.05 mg/m3 8-hour time-weighted average. Driven by glass cullet, construction and demolition waste, and any inert recycling stream. Reduced from 0.1 to 0.05 in 2020.
• Lead: 0.05 mg/m3 8-hour TWA. Driven by e-waste shred, CRT breakage, lead-acid battery recycling.
• Mercury (vapour): 0.025 mg/m3 8-hour TWA. Driven by fluorescent lamp recycling.
• Beryllium: 0.0002 mg/m3 8-hour TWA. The most stringent metal limit in the recycling sector. Driven by some legacy electronic substrates and certain alloy waste streams.
• Cadmium: 0.01 mg/m3 8-hour TWA. Driven by e-waste, especially nickel-cadmium battery legacy stock.
• Hydrogen fluoride: 3 ppm short-term exposure limit (15-minute), 1.8 mg/m3 ceiling. Driven by lithium-ion battery thermal runaway and certain fluoropolymer thermal decomposition. Highest acute hazard in the sector.
• Hydrogen bromide: 3 ppm ceiling. Driven by brominated flame retardant decomposition and lithium-ion battery thermal runaway.
• Hydrogen chloride: 5 ppm ceiling. Driven by PVC thermal decomposition in shredder fires.
• PFAS: No formal WES in Australia at 2026 publication, but several state EPAs have introduced advisory limits in the range 0.005 to 0.05 mg/m3. Driven by aqueous film-forming foam contamination of training-ground waste and certain industrial residual streams.

The duct design must hold airborne concentrations below the WES at every breathing-zone receptor. The calculation runs forward from the contaminant generation rate at the source, through the dilution by general ventilation and the capture by local extract, to the residual concentration at the operator position. A duct system that meets AS 1668.2 mechanical ventilation rate but fails the WES at the breathing zone is non-compliant — process exhaust is the operative driver, not general ventilation.

Boundary air quality, AS 3580 and NEPM Air Toxics

The duct discharge from any recycling facility is bounded by the receptor air quality at the residential boundary. The operative standards are AS 3580 (boundary air monitoring methods) and the National Environment Protection Measure for Air Toxics, which set ambient air quality goals at the receptor for benzene, formaldehyde, polycyclic aromatic hydrocarbons, toluene, xylenes and benzo[a]pyrene. The state EPA licence conditions translate the NEPM goal to a stack discharge limit through dispersion modelling.

The duct design implications are stack height, stack velocity and stack location. Stack height is set against dispersion modelling — typically 1.5 to 2.5 times the height of the tallest building within 100 metres, with corrections for terrain and wind rose. Stack velocity is typically 15 to 25 m per second to ensure plume rise and to clear the building cavity. Stack location is set against the residential boundary and the public access positions. The stack itself is normally 304L stainless or 316L stainless because solar and discharge thermal cycling rapidly degrades galvanised in this service.

Operator boundary monitoring is a state EPA licence condition. AS 3580 sets the methods — high-volume sampler for particulate, sorbent tube for VOC, real-time CO and SO2 instruments where required. Complaint risk from the residential boundary is a leading reason that recycling facilities require expensive duct upgrades through the operational life — a complaint pattern triggers a state EPA review which typically prescribes additional capture or treatment at the source. Designing the duct to clear the receptor target with margin at commissioning is significantly cheaper than retrofitting later.

Hazardous area zoning under AS/NZS 60079

AS/NZS 60079 is the Australian and New Zealand hazardous area standard, addressing explosive gas atmospheres. The recycling facility zones that typically classify:

• Lithium-ion battery shredder enclosure: Zone 1 inside the enclosure during normal operation, Zone 2 in adjacent rooms during fault conditions.
• Anaerobic digestion biogas paths: Zone 0 inside the digester and the biogas pipework, Zone 1 in adjacent areas, Zone 2 in larger plant rooms. Continuous H2S and CH4 detection mandatory.
• FOGO compost tunnels: Zone 2 inside the tunnel where methane evolution is credible, particularly in the early thermophilic stage.
• Paper bale storage tunnels: Zone 2 where CO and CH4 evolution from microbial decomposition approaches the lower flammable limit. Continuous CO detection mandatory.
• Solvent-bearing plastic recycling streams: Zone 1 or Zone 2 depending on the solvent inventory and the ventilation regime.

The HVAC duct in a hazardous area must be earth-bonded to prevent static accumulation, the fan motor must be rated to the zone classification (typically Ex e or Ex d construction), and the gas detection must be intrinsically safe to Ex ia. Routine isolation valves and dampers must be rated to the zone classification or located outside the hazardous area. The hazardous area zoning is documented in the project safety file alongside the AS 3957 dust hazard assessment.

SBKJ machinery suitability across the recycling duct package

The Australian fabricator pricing a recycling or sortation facility duct package needs a machinery line that covers the rectangular galvanised majority, the round return-air component, the heavy-gauge stitchwelded shredder pre-vent, the 304L and 316L stainless stainless and the special bracketry. The SBKJ machinery offer maps to the duct package as follows.

• SBAL-V auto duct line. 16 m per minute production speed, 87 kW total connected load, 0.5 to 1.5 mm gauge range, 1500 mm maximum coil width. Covers the rectangular galvanised majority of the project — tipping floor extract, sortation hall extract, conveyor capture, optical sortation extract, eddy current and magnetic separator capture, baler extract, Container Deposit Scheme depot general extract, paper bale storage ventilation, glass cullet handling, refuse-derived fuel shredder extract, plastic recycling general supply. Configurable for 304L and 316L stainless with the stainless tooling package, covering CRT, mercury, e-waste shredder extract, lithium-ion battery shred extract, compost biofilter return and plastic flake wash extract. See SBAL-V product page for full specifications.
• SBAL-III auto duct line. 14 m per minute, 15.7 kW. Lower-throughput alternative to SBAL-V for fabricators with smaller project mix. Covers the same materials range.
• SBAL-II auto duct line. 18 m per minute, 5.5 kW. Entry-level auto duct line for small-volume specialty work.
• SBTF-1500C / SBTF-1602 / SBTF-2020 spiral tubeformers. Round duct production for return-air sections, ducted transitions between rectangular main and scrubber inlet, stack tie-ins. Different models cover different diameter ranges and gauge schedules. Stainless configuration available.
• SBEM-1250 elbow making line. Round-duct elbow production for the return-air and stack tie-in sections.
• SBSF-1525 stitchwelder. 2.5 kW. Continuous welded longitudinal seams on heavy-gauge galvanised and 304L stainless. Mandatory for the shredder pre-vent, lithium-ion battery shred extract, NFPA 660 deflagration-rated sections, and any service above AS 4254.2 medium-pressure class. See SBSF-1525 product page.
• SBFB-1500 folder. 7.5 kW, 1.20 m per minute. Heavy-gauge folded sections around access doors, transitions, bracketry and reinforcement frames. Covers the special fabrication that does not fit through the auto duct line.
• SBHF hydraulic folding machine. Heavy-gauge plate folding for stack saddles, scrubber inlet plates and reinforcement plates.
• SBPC1500 plasma cutter. 1500 mm cutting width for 304L and 316L stainless plate work, scrubber inlet cut-outs, access door cut-outs, branch take-offs.
• SBLR-600 / SBLR-600A roll bender. 7.6 m per minute. Radius transitions on stack tie-ins, scrubber inlet bends, large-radius duct bends where the auto duct line cannot deliver the geometry.

A representative machinery line for an Australian fabricator pricing recycling and sortation work as a primary segment is one SBAL-V auto duct line, one SBTF-1500C spiral tubeformer, one SBSF-1525 stitchwelder, one SBFB-1500 folder and one SBLR-600A roll bender. The total connected load is around 115 kW, the footprint is around 600 to 800 square metres, and the fabrication throughput is around 1,200 to 1,800 m2 of finished duct per shift. The machinery investment typically pays back within 2 to 3 Australian MRF or recycling facility projects relative to imported pre-fabricated duct, after which it covers maintenance retrofits and adjacent industrial work across the operator's local region.

For fabricators with primary work in battery recycling or hazardous waste, the machinery line is augmented with stainless tooling on the SBAL-V (extra cost in the 12 to 18 percent range), additional stitchwelder capacity (a second SBSF-1525 running parallel), and increased plasma cutter capacity (SBPC1500 with second torch for productivity). For fabricators with primary work in Container Deposit Scheme depots and small-volume general waste sortation, the line can be reduced to a single SBAL-III with one SBTF-1500C, covering the duct package at lower capital cost.

Adjacent industry references

The Australian recycling and sortation sector shares technical territory with several adjacent industries the SBKJ catalogue addresses in dedicated guides. Specifiers cross-referencing experience benefit from the comparisons.

• Battery gigafactory HVAC — the lithium-ion thermal runaway controls applied in battery recycling shred lines are the reverse problem of those applied at the cell manufacturing end. See our battery gigafactory HVAC duct guide for the cell-side perspective on the same chemistry.
• Composite manufacturing — the brominated flame retardant and styrene VOC capture in plastic recycling overlaps the composite manufacturing exhaust regime. See our composite manufacturing HVAC duct guide.
• Cement plant alternative fuel — the refuse-derived fuel exit from the recycling facility feeds the cement kiln. See our cement plant HVAC duct guide for the kiln-side perspective.
• Steel mill and smelter — the ferrous metal recycling at Sims feeds the electric arc furnace stream. See our steel mill and smelter HVAC duct guide.
• Mining ventilation — the silica dust controls applied in glass cullet handling are conceptually similar to underground mine intake and return ventilation. See our mining ventilation HVAC duct guide.
• Australia HVAC duct fabrication setup — for the fabricator setting up an Australian shop to service recycling and sortation projects, see our Australian HVAC duct fabrication setup 2026 guide.
• AS 1668.2 Australian ventilation code — for the full reference on the operative ventilation standard, see our AS 1668.2 reference.

Cost benchmarks and budget guidance

HVAC ductwork including supply, return, exhaust, scrubber interstage and stack on an Australian recycling or sortation facility typically represents 4 to 8 percent of total facility capital cost. For a typical 100,000 to 250,000 tonne per annum MRF with capital cost in the AUD 30 to 80 million range, this implies AUD 1.5 to 5 million in ductwork material, fabrication and installation. Within this:

• General supply and return (galvanised G90): 35 to 45 percent of total ductwork spend.
• Process extract and capture (galvanised G90 with stitchwelded heavy-gauge sections): 25 to 35 percent.
• Specialist process room extract (304L and 316L stainless): 10 to 20 percent. Concentrated on e-waste, CRT, mercury, battery shred, compost biofilter return.
• Scrubber stack and discharge: 5 to 10 percent.
• Insulation, protection and fire-rated penetration sealing: 8 to 12 percent of installed ductwork cost.

For an e-waste or battery recycling facility the stainless proportion climbs to 35 to 50 percent of total tonnage and the total ductwork cost share of facility build rises to 8 to 12 percent. For a Container Deposit Scheme depot the ductwork share is at the lower end — 3 to 5 percent — because the duct package is small relative to the conveyor and reverse-vending equipment.

The fabrication labour share is what local on-site fabrication with appropriate duct-forming machinery directly attacks. Moving from imported pre-fabricated duct to local fabrication on an Australian shop with an SBKJ machinery line typically reduces installed cost by 15 to 25 percent on the stainless work and by 10 to 15 percent on the galvanised work, accounting for machinery capital amortisation, operator training and shop overhead. The lead-time benefit is significant on the stainless work — local fabrication delivers in 4 to 6 weeks against 14 to 22 weeks for imported pre-fabricated.

Validation, commissioning and ongoing compliance

HVAC commissioning on a recycling facility is more rigorous than general industrial HVAC because the duct system is a primary process safety system. The validation suite typically includes:

• Pressure decay testing on completed duct sections before insulation and concealment. Tightness verification at 1.5 times design static pressure for 15 minutes minimum. Sections that fail are repaired and re-tested before sign-off.
• Capture velocity verification at every local extract hood with calibrated anemometer. ACGIH IV Manual target plus or minus 10 percent at the design face position.
• Air change rate verification by tracer gas decay or anemometric supply measurement on every zone. Verified to plus or minus 10 percent of AS 1668.2 design.
• Pressure cascade verification at every airlock with all doors closed and worst-case door-open scenarios. Calibrated micromanometer to 0.5 Pa resolution.
• Smoke test capture verification at every hood with smoke generator. Visual confirmation of capture to within the design face position.
• Baghouse pressure drop characterisation across the filter loading cycle, with the operational alarm threshold set at 1.5 times clean-filter pressure drop.
• Explosion vent inspection on every NFPA 68 vent panel before commissioning, with the rupture pressure verified against the design Kst.
• Gas detection calibration with reference gas at multiple concentrations on every CO, H2, HF, HBr, HCl, H2S, CH4 and O2 sensor.
• Fire damper drop test on every AS 1682 damper with command from BMS, verifying actuator response time and the fail-closed position.
• Personal monitoring against Safe Work Australia WES for the active contaminants on the project — respirable crystalline silica, lead, mercury, beryllium, cadmium, HF as applicable.
• Boundary monitoring against AS 3580 at the residential receptor for at least 30 days of continuous operation.
• Stack emissions sampling against the state EPA licence condition for the discharge.

The full commissioning report is a deliverable to the operator and is required documentation for the operations and maintenance handover. The ongoing compliance regime typically runs daily collector pressure drop logging, weekly explosion vent visual inspection, monthly gas detector calibration, 12-monthly AS 1851 fire damper drop test, 5-yearly AS 3957 dust hazard re-validation, and continuous boundary monitoring against AS 3580 and NEPM Air Toxics. The duct system operational records feed the operator's ISO 14001 environmental management system, where applicable, and the state EPA licence reporting cycle.

How SBKJ engages an Australian recycling duct project

From Box Hill North, Victoria, SBKJ engages an Australian recycling or sortation facility duct project across three phases.

Phase 1 — concept design support. An SBKJ mechanical engineer reviews the consulting engineer's concept duct schedule and identifies the zones, materials and construction class. The engineer recommends a machinery line that covers the duct package at the fabricator's target throughput, with a configuration that handles the stainless and stitchwelded sections without forcing the fabricator to sub-contract. The output is a single-page machinery recommendation and a budgetary capital estimate for the fabricator's project tender.

Phase 2 — detail design fabrication and machinery commissioning. Once the project is awarded, the SBKJ engineer works with the fabricator on the duct-by-duct take-off, the gauge schedule, the welding procedure for the stitchwelded sections and the tooling configuration on the auto duct line. The machinery is shipped, installed and commissioned by SBKJ engineers on the fabricator's site, with operator training delivered in English. Lead time from machinery order to commissioning is 16 to 22 weeks, comparable to European-built alternatives. See the full machine catalogue.

Phase 3 — operational support and spare parts. SBKJ provides a 10-year minimum parts support commitment in writing, in line with the typical 15 to 20 year operational horizon of an Australian recycling facility. Spare parts are held in Box Hill North for next-day dispatch across the Australian east coast and in the SBKJ Australian distribution network for the broader Pacific region. Operator training records are maintained as part of the fabricator's ISO 14001 EMS.

Discuss your Australian recycling or sortation duct project with SBKJ →

FAQ

How many ACH do I need on an Australian MRF tipping floor under AS 1668.2?

AS 1668.2 frames the requirement as process exhaust against the contaminant load and the receptor limit. In practice, Australian MRF tipping floors run 6 to 10 ACH of general ventilation with localised capture at the tip face and any sortation positions. Where the receival floor abuts a residential boundary, the rate climbs to 10 to 15 ACH and the floor is held under negative pressure of 12 to 25 Pa relative to the boundary. Boundary discharge is routed through an odour treatment train before stack release at a height set against AS 3580 receptor positions and the state EPA licence.

What is the most dangerous airborne hazard in an Australian e-waste facility?

Two hazards lead. First, heavy metal dust from shredding — lead, cadmium, mercury and beryllium are all present in legacy electronics and all have Safe Work Australia WES at or below 0.05 mg/m3. Second, lithium-ion thermal runaway from undeclared cells in the feed stream. A single cell can ignite a deflagration through the surrounding paper and plastic dust load and release HF, HBr and PF5 into the extract duct. HVAC duct response is HEPA H13 or H14 final filtration for the heavy metal capture and explosion-vented, spark-resistant pre-extract for the battery ignition risk.

How is lithium-ion battery thermal runaway managed in a battery recycling shredder hood?

Four layers under NFPA 855 and AS/NZS 5139. First, inerted shredder enclosure under continuous nitrogen or argon blanket. Second, NFPA 68 explosion vent panels on the shredder and downstream baghouse, discharging through welded heavy-gauge duct to a safe outdoor location. Third, three-stage scrubber train — caustic primary for HF and HCl, acid secondary for ammonia, activated carbon polish for organic carbonates. Fourth, continuous gas detection (HF, HBr, HCl, H2, CO, O2) interlocked to fast-acting isolation dampers, inert gas knock-down and process trip. Stack discharge monitored continuously for HF, HBr, HCl and total VOC.

What duct material should I specify for a CRT breakage room?

304L stainless steel with welded longitudinal seams. The room is held at strong negative pressure of 15 to 25 Pa relative to surroundings. Duct velocity 18 to 22 m/s to keep lead dust entrained. HEPA H13 or H14 final filtration before any discharge. Stack in 304L stainless. The choice of stainless is for ease of decontamination at end-of-life rather than corrosion resistance — galvanised would survive the chemistry, but stainless allows wipe-down and licensed lead waste recovery when the room is eventually decommissioned.

What duct material between a battery shredder and a three-stage scrubber stack?

Layered by stage. Shredder hood to baghouse run is welded heavy-gauge galvanised or 304L stainless designed against deflagration pressure pulse. Baghouse to primary caustic scrubber run is 304L stainless because the gas stream contains residual HF, HBr and PF5. Primary caustic scrubber body normally FRP (outside SBKJ scope). Scrubber-to-scrubber interstage 316L because of chloride from caustic carryover. Acid scrubber-to-carbon-polish run 316L. Carbon polish-to-stack 304L. Final stack 304L with continuous emissions monitor for HF, HBr, HCl and total VOC.

How is bioaerosol from a compost trommel managed?

Fully enclosed trommel housing under negative pressure of 25 to 50 Pa, extract at 4 to 6 m/s capture velocity, routed to an open-bed wood-chip or bark biofilter with 30 to 45 second residence time, irrigated to 50 to 65 percent moisture. Extract duct between trommel and biofilter is 316L stainless because compost off-gas is humid, organic-acid-laden and condensing. Open-bed biofilters discharge to atmosphere; enclosed biofilters with a stack are sized against AS 3580 receptors.

What capture velocity at an optical sortation NIR camera line?

Upstream dust suppression by enclosed conveyor hoods, localised extract above each camera bank at 0.3 to 0.5 m/s face velocity, dust capture hood at air-knife discharge chutes at 0.5 to 0.8 m/s. Total extract volume for a 60 tonne per hour MRF optical line is 8,000 to 14,000 m3/h to a baghouse with PTFE membrane filter media. Duct galvanised G90 with stitchwelded longitudinal seams to AS 4254.2.

What Safe Work Australia WES bind a recycling facility design?

Respirable crystalline silica 0.05 mg/m3 (glass, construction waste), lead 0.05 mg/m3 (e-waste, CRT, lead-acid battery), mercury vapour 0.025 mg/m3 (fluorescent lamp), beryllium 0.0002 mg/m3 (legacy electronics), cadmium 0.01 mg/m3 (e-waste, Ni-Cd battery legacy), hydrogen fluoride 3 ppm STEL (lithium-ion thermal runaway), hydrogen bromide 3 ppm ceiling (brominated flame retardant, Li-ion), hydrogen chloride 5 ppm ceiling (PVC thermal decomposition). PFAS has no formal WES at 2026, but several state EPAs have advisory limits in the 0.005 to 0.05 mg/m3 range.

What machinery line covers a typical Australian recycling facility duct package?

One SBAL-V auto duct line (16 m/min, 87 kW, 0.5 to 1.5 mm, 1500 mm) for the rectangular galvanised majority and the stainless work in 304L and 316L. One SBTF-1500C spiral tubeformer for round return-air. One SBSF-1525 stitchwelder (2.5 kW) for the welded heavy-gauge shredder pre-vent and battery extract. One SBFB-1500 folder (7.5 kW, 1.20 m/min) for special bracketry. One SBLR-600A roll bender (7.6 m/min) for radius transitions. Total connected load around 115 kW, footprint 600 to 800 m2, throughput 1,200 to 1,800 m2 of finished duct per shift. Payback typically 2 to 3 MRF projects.

How much does HVAC ductwork cost as a percentage of an Australian recycling facility build?

4 to 8 percent of total facility capital cost for a typical 100,000 to 250,000 tonne per annum MRF — AUD 1.5 to 5 million on a AUD 30 to 80 million build. e-Waste and battery recycling facilities run higher at 8 to 12 percent because of the stainless content. Container Deposit Scheme depots run lower at 3 to 5 percent because the duct package is small relative to the conveyor and reverse-vending equipment. Within the package, general galvanised supply and return is 35 to 45 percent, process extract 25 to 35 percent, specialist stainless 10 to 20 percent, scrubber stack 5 to 10 percent, insulation and fire-rated penetration sealing 8 to 12 percent.