Recycling and Waste Sorting Facility HVAC Duct Guide — Cleanaway, Veolia, Visy, MRF Dust, Odour Control

Why recycling facility HVAC is unlike anything else in industrial ventilation

HVAC for a Materials Recovery Facility, e-waste shredder hall or organics composting plant is the most demanding industrial ventilation discipline in the Australian built environment. A food-processing exhaust system fights humidity and oil mist. A mining ventilation system fights diesel particulate and silica. A cold chain duct fights condensation. A recycling facility duct fights all of those at once — paper fibre dust loaded into the airstream, mixed plastic shred carrying volatile organics, organic putrescible material releasing hydrogen sulphide and ammonia, lithium cells incorrectly sorted into the shredder feed, and a 24/7 operational schedule that allows almost no shutdown window for maintenance.

Five conditions distinguish recycling facility HVAC from every other industrial application:

• Heavy and variable dust loading. A kerbside MRF tipping floor shifts from a paper-dominant load on Monday morning kerbside collection to a glass-and-metal dominant load on Tuesday afternoon. The duct system must handle paper fibre at one shift and shredded HDPE the next without re-engineering.
• Odour management as a planning condition. Most Australian recycling facilities operate under EPA licence conditions that prescribe maximum odour concentration at the site boundary. Failure to meet the boundary condition triggers planning-permit reviews that can shut a facility for months. The duct system that connects the tipping floor capture hood to the chemical scrubber and stack is the single most important compliance asset on site.
• Worker biohazard exposure. Medical waste autoclaving, sewage sludge dewatering, mixed municipal solid waste sorting and contaminated soil handling all carry pathogen exposure risks. The HVAC system maintains negative-pressure containment of contaminated zones and provides positive-pressure refuges for worker breathing zones.
• Explosion risk from multiple ignition sources. Paper fibre dust at NFPA 484 / 654 St-1 classification, plastic shred dust at St-1, wood dust commonly at the high end of St-1 or into St-2, and lithium battery thermal runaway that can simultaneously generate hydrogen, hydrogen fluoride and ethylene at temperatures sufficient to ignite the surrounding dust load. No other industrial ventilation discipline routinely deals with this combination.
• 24/7 operation with constrained shutdown windows. Cleanaway, Veolia and Visy all run their major MRFs on continuous shifts with planned shutdown only at Christmas and Easter. Any HVAC component that requires more than a 48-hour outage to service is unacceptable. Duct system design must reflect that reality with full inspection access, redundant flow paths and plug-in collector cartridges.

Recycling facility types and their HVAC fingerprints

Before specifying any duct, classify the facility. The HVAC duct system that suits a kerbside MRF is wrong for an e-waste shredder, and the duct that suits a composting hall is unsafe for an anaerobic digestion biogas path. Australian recycling operations fall into nine broad categories:

Materials Recovery Facility (MRF)

The kerbside recycling backbone. A typical Australian capital-city MRF processes 100,000–250,000 tonnes per annum of mixed paper, cardboard, plastic containers, glass, aluminium and steel cans. Tipping floor receives co-mingled material, sorting line uses optical sorters, eddy-current separators, magnetic separators and air knives, and bales of separated commodity discharge to outbound load-out. Major Australian operators include Cleanaway, Veolia, Visy Recycling, Re.Group, Polytrade and SUEZ Recycling and Recovery (now part of Veolia globally but retaining a distinct Australian footprint in some assets).

HVAC fingerprint: high paper-fibre dust load on the sorting line, moderate odour load on the tipping floor (kerbside material is not heavily putrescible if collected fortnightly), explosion classification St-1 dust hazard, 24/7 operation. Duct material is overwhelmingly galvanised G90 with stainless used only on glass-crushing exhausts where moisture and abrasion shorten galvanised life.

Construction and Demolition (C&D) recovery

Concrete crushing, timber recovery, plasterboard recovery and metal salvage. HVAC fingerprint dominated by silica dust (concrete) and wood dust. Wood dust is among the most aggressive combustible dust in any industrial setting — Kst values commonly above 200 bar.m/s. The duct material is galvanised but the explosion protection is the dominant design driver.

E-waste / WEEE processing

Computers, phones, batteries, white goods, screens. Process flow runs through manual de-pollution (battery removal, screen removal), shredding, magnetic and eddy-current separation, density separation, and downstream metal recovery (often subcontracted to specialist smelters off-site). HVAC fingerprint: high dust load on the shredder, lithium battery thermal runaway risk, mercury exposure on fluorescent tube and old LCD processing, lead exposure on solder dust. Duct materials shift toward stainless 304 in acid-leaching auxiliary processes and welded steel for shredder transport ducts. Explosion protection is the single largest cost item in the HVAC scope.

Plastic recycling

PET bottle washing and flaking, HDPE rigid recycling, mixed plastic pyrolysis (emerging), film and soft plastic recycling. HVAC fingerprint: shredding dust, melt extrusion VOC emissions during pelletising, pellet bagging dust extraction, wash-line humidity. Duct materials lean toward polyethylene-lined steel on the extruder exhaust and stainless on the wash-line where chlorinated wash water can be present.

Tyre recycling

Mechanical shredding to crumb rubber. HVAC fingerprint: rubber dust, hydrocarbon vapour, fire risk in storage. Galvanised duct is standard, but the dust collector and fire suppression are the dominant capital line.

Organics composting and FOGO

Food Organics Garden Organics is the flagship policy push by every Australian state EPA, with FOGO bins mandated or strongly incentivised for kerbside collection from 2024 onward. Composting halls, in-vessel composting and windrow operations all require HVAC for both worker exposure (high humidity, ammonia, bioaerosols) and odour management. Duct materials skew to FRP or polyethylene-lined steel due to chronic high humidity (often 95% relative humidity) and corrosive ammonia exposure.

Anaerobic digestion (AD)

Often co-located with FOGO composting, AD generates biogas (CH4 plus H2S plus CO2) that is then used in a combined heat and power (CHP) plant on site. HVAC fingerprint: biogas piping is a hazardous area to AS/NZS 60079, hydrogen sulphide is corrosive at 50–500 ppm levels typical in raw biogas, and CHP exhaust is a separate scope. Duct material is 316L stainless for biogas paths or polyethylene-lined steel; carbon steel will fail within months on raw biogas.

Hazardous waste

Solvent reclamation, lead-acid battery recycling, mercury-bearing waste, cyanide gold recovery (rare in Australia but does exist), drum cleaning, contaminated industrial liquid stabilisation. HVAC fingerprint: chemical-specific exhaust trains, wet scrubbers, acid mist control, mercury vapour control. Duct material is heavily stainless and FRP with full welded joints.

Medical waste autoclaving and incineration

Australian medical waste is overwhelmingly treated by autoclave (large-scale operators include Daniels Health, Stericycle and various state-by-state contractors). HVAC fingerprint: autoclave exhaust at high humidity and temperature, drain odour, downstream shredding of treated material, HEPA H13 final filtration on extract. Where incineration is used (rare in Australia, more common for cytotoxic and pathological waste), the incinerator exhaust itself is a separate emissions-control scope but the building HVAC must address ash handling dust and refractory replacement maintenance dust.

Soil remediation

Thermal desorption (indirect-fired or direct-fired), bioremediation, soil washing. HVAC fingerprint: hot exhaust gas handling (200–350 °C from desorbers), hydrocarbon vapour, dust from screening. Duct material is high-temperature insulated stainless steel on the desorber path with a downstream after-burner or thermal oxidiser to destroy residual VOC.

The Australian regulatory and policy backdrop

Recycling facility design in Australia today cannot be understood without the policy backdrop that has reshaped the sector since 2018.

The key inflection point was the 2018 international import restrictions on mixed paper and contaminated plastic from major Asian importers — the so-called "National Sword" policy. Australia had been exporting roughly 1.25 million tonnes of recyclable material annually to offshore reprocessors, and the import restrictions effectively closed that market overnight. The federal response, formalised in 2020, was the Recycling Modernisation Fund — approximately AUD 250 million from the federal government plus matched state and industry contributions taking total committed capital to roughly AUD 1 billion across 2020–2026. Every Australian state EPA has set parallel resource recovery targets — Victoria's target of 80% diversion from landfill by 2030, New South Wales' target of 80% by 2030, Queensland's parallel program, South Australia's long-running and most-aggressive program, Western Australia's Waste Avoidance and Resource Recovery Strategy 2030, and ACT, Tasmania and Northern Territory parallel frameworks.

Container Deposit Schemes have rolled out progressively across every state and territory: NSW Return and Earn (2017), QLD Containers for Change (2018), ACT (2018), WA Containers for Change (2020), VIC CDS Vic (2023), TAS Recycle Rewards (2025) and parallel arrangements in SA (the original, since 1977) and the NT (since 2012). Each CDS scheme drives a parallel network of automated processing centres that have their own HVAC duct requirements — typically galvanised low-pressure for general ventilation and HEPA-filtered extract on baling lines.

FOGO kerbside rollout — Food Organics Garden Organics — has been state-led with Victoria and New South Wales pushing hard from 2024 onward. The result is a wave of new and expanded composting and anaerobic digestion facilities that need HVAC duct designed against the unique challenge of high-humidity, high-ammonia, high-hydrogen-sulphide air streams.

Practically, this policy backdrop means new Australian recycling facilities are being designed and built to higher specifications than the pre-2018 benchmark. The export market for low-grade material is gone, so the on-shore facility must produce export-grade or domestic-feedstock-grade output. That requires better dust capture (so paper bales are not contaminated with plastic film), better odour control (so neighbouring communities accept facility expansion), and more rigorous explosion protection (so insurance underwriters will write the policy).

Major Australian recycling operators and their facility patterns

Understanding the operators is the fastest way to understand the facility design language. The Australian recycling sector is dominated by a half-dozen operators with distinct facility patterns.

Cleanaway

Australia's largest waste management company. Operates MRFs across every capital city plus many regional centres. Cleanaway's MRF design language tends toward larger-scale single-stream facilities — Eastern Creek (Sydney) and Erskine Park are reference designs. Their HVAC pattern uses galvanised G90 ductwork on most paths, baghouse dust collection with explosion vent panels per NFPA 68, and chemical odour scrubbers on tipping floor exhaust. Cleanaway also operates resource recovery for organic waste and a growing footprint in plastic recycling.

Veolia Australia

The Australian arm of the French Veolia group, expanded significantly with the 2022–2023 acquisition of SUEZ Recycling and Recovery's Australian operations. Veolia operates MRFs, hazardous waste treatment (notably at Lytton in Brisbane), composting and anaerobic digestion. Veolia's facility design language draws from European parent-company standards and tends toward more sophisticated odour control trains — typically a chemical scrubber primary stage followed by carbon polishing — and earlier adoption of stainless 316L on aggressive process exhausts.

Visy Recycling

The recycling arm of the Pratt Industries / Visy paper and packaging group. Visy is the dominant Australian processor of kerbside paper and cardboard, with MRFs in every state and parallel paper mill assets that consume the recovered fibre. Visy's MRF design language is paper-fibre-dominant — heavier dust loads on the sorting line than a Cleanaway mixed-MRF, and heavier explosion protection capital allocated to baghouse and paper bale storage areas. HVAC pattern is galvanised G90 throughout with PTFE membrane bag filters on the dust collector.

Pact Group

The dominant Australian plastic packaging company with an expanding plastic recycling footprint, including the Albury PET recycling facility (operated as a joint venture with Cleanaway and Asahi Beverages) commissioned 2022. Pact's plastic recycling HVAC pattern reflects the wash-line plus extruder pattern — polyethylene-lined steel on extruder exhaust, stainless on wash-line discharge, and HEPA filtration on the pellet bagging exhaust.

Polytrade

A specialist Australian paper recycling and bale-export operation. Polytrade's facility pattern is paper-dominant with strong fibre-dust loads on the sorting line, similar in HVAC fingerprint to Visy though at smaller per-facility scale.

Re.Group

Mid-tier Australian operator running MRFs and resource recovery facilities, often under contract with regional councils. Re.Group's facility pattern is similar to a downscaled Cleanaway MRF.

Renewi Australia

Commercial and industrial waste collection and processing, more focused on transfer stations and commercial-volume processing than household kerbside. HVAC pattern at the transfer station scale is simpler — general ventilation plus localised dust capture at tipping points, rarely the full explosion-protected baghouse and odour scrubber train of a kerbside MRF.

Daniels Health, Stericycle and Cleanaway HSE

The dominant Australian medical waste operators. HVAC pattern is autoclave-exhaust-dominant with HEPA H13 final filtration and dedicated negative-pressure containment on sharps and infectious waste sorting.

Standards and codes for recycling facility HVAC

Australian recycling facility HVAC duct design draws from a hybrid stack of Australian Standards, NFPA prescriptive standards (used as technical reference even where not legally mandated), and ACGIH ventilation guidance. The full applicable stack on a typical large MRF project includes the following:

AS 1668.2 — Mechanical ventilation in buildings

The base building ventilation standard. Sets minimum outside-air rates per occupant and per floor area, defines mechanical ventilation classifications, and underpins building-permit compliance. AS 1668.2 does not prescribe industrial process ventilation rates — it is a general building standard — but every Australian recycling facility must satisfy it as a baseline.

AS 4655 — Performance of dust collection equipment

The Australian standard governing dust collector performance and test methodology. Establishes specification language used in tender documents.

AS/NZS 4360 — Risk management framework

The principles-based risk management standard that underpins the Dust Hazard Analysis approach used in Australia. Most Australian fire engineers deliver the DHA as an AS/NZS 4360 risk study using NFPA 654 as the technical reference for combustible dust parameters.

AS/NZS 4254 — Ductwork for air handling systems

The duct construction standard equivalent to SMACNA in North America and EN 1505 / EN 1506 in Europe. Covers gauge selection, reinforcement, leak class and installation. SBKJ machinery is configured to AS/NZS 4254 dimensions and tolerances by default for Australian-bound projects.

AS/NZS 60079 series — Explosive atmospheres

Hazardous area classification and equipment selection. Critical for anaerobic digestion biogas paths, e-waste shredder hoods (where lithium thermal runaway is the trigger gas) and any solvent-bearing exhaust. Drives selection of intrinsically safe gas detectors, EX-rated motors and certified exhaust fans.

AS 3580 — Methods for sampling and analysis of ambient air

Underpins EPA-required ambient air monitoring at facility boundaries. Drives stack-discharge design — height, exit velocity, plume rise — to ensure the boundary monitoring positions remain compliant.

NFPA 484 — Combustible metals

Used as the prescriptive technical reference for any metal-bearing dust (e-waste, C&D metal recovery). Covers titanium, magnesium, aluminium and combustible metal alloy dust hazards.

NFPA 654 — Industrial particulate solids

The dominant prescriptive standard for combustible particulate solids — paper dust, plastic dust, wood dust, sugar dust, organic dust. Used as technical reference in Australian DHA work.

NFPA 91 — Exhaust systems

Prescriptive standard for industrial exhaust systems handling combustible particulate, vapour and mist. Covers velocity limits, duct material selection, cleaning and inspection access. Used as technical reference in Australian work where AS/NZS does not provide equivalent detail.

NFPA 68 — Standard on explosion protection by deflagration venting

Sizing standard for explosion vent panels. Applied to baghouse and cyclone collectors handling combustible dust.

NFPA 69 — Standard on explosion prevention systems

Covers isolation devices — chemical isolation, mechanical valves, rotary airlocks — that break propagation of a deflagration back to upstream process equipment.

ATEX 137 / 153 (Europe)

The European equivalent dust zoning framework. Cited in equipment specifications because most explosion protection hardware sold in Australia carries ATEX marking from European manufacturers (Rembe, Fike, IEP Technologies). Australian operators routinely accept ATEX certification as evidence of compliance.

ACGIH Industrial Ventilation Manual

The American Conference of Governmental Industrial Hygienists IV Manual is the global reference for hood capture velocity design. Every Australian fire engineer, industrial hygienist and HVAC consultant working on recycling facilities will reference the ACGIH IV Manual for capture velocity selection.

Tipping floor HVAC — the odour-control front line

The tipping floor is where collection trucks discharge into the facility. It is the largest single airborne emission source in any MRF and the primary surface of contact with neighbouring communities. EPA licence conditions almost always reference odour at the boundary, and the tipping floor HVAC system is the asset that makes or breaks compliance.

Typical tipping floor design parameters in Australian MRFs:

• General ventilation rate: 4–8 air changes per hour minimum, often higher (6–10 ACH) on tipping floors handling MSW with significant putrescible content.
• Pressure regime: negative relative to amenity, office and outbound load-out areas. Differential typically -25 Pa to -50 Pa.
• Capture hoods: at the tipping face, designed to ACGIH IV Manual capture velocity 0.5–1.0 m/s at the breathing zone of the truck driver.
• Doors: rapid-action high-speed roller doors at vehicle entry, with air curtains for additional containment.
• Odour control train: tipping floor exhaust ducted to a primary scrubber (chemical or biofilter), polishing carbon, then stack discharge. Fan capacity sized for the full hood plus general ventilation airflow.

Odour control technology selection follows the load:

• Activated carbon scrubbers — appropriate for low-concentration mixed VOC and sulphide loads typical of kerbside MRFs. Capital is moderate, OPEX is dominated by carbon replacement at typically 3–6 month intervals.
• Biofilters — open-bed or enclosed-bed systems where a microbial population on a packed media (bark, woodchip, compost) biologically degrades odour compounds. Best suited to FOGO and organics-heavy streams. CAPEX is moderate, OPEX is low, but footprint is large (typically 50–100 m² per 50,000 m³/h treated).
• Chemical scrubbers — caustic (sodium hydroxide), sodium hypochlorite or hydrogen peroxide solutions with packed-tower contact. Best suited to higher-concentration loads and hydrogen sulphide spikes from MSW or anaerobic digestion. Higher CAPEX and OPEX than carbon, but very effective.
• Multi-stage trains — most large operators run a chemical scrubber primary stage followed by carbon polishing. The chemical stage handles the heavy load, the carbon polish protects the stack discharge against transient excursions.

Duct material between the tipping floor capture and the chemical scrubber inlet is typically galvanised G90 because the air at that point is dry. Between the chemical scrubber wet sections and the stack, duct is FRP, polyethylene-lined steel or 316L stainless because the air is saturated with moisture and acidic chemicals.

Sorting line HVAC — dust capture as a productivity asset

The sorting line is where dust generation is highest. Optical sorters use compressed-air ejection (air knives) to redirect targeted material from the mainstream — every air-knife pulse generates a dust burst. Trommels, ballistic separators, eddy-current separators and magnetic head pulleys all generate dust as they tumble and sort the material stream.

Sorting line dust capture design parameters:

• Hood design: dedicated capture hoods at every air-knife discharge, optical sorter exit, trommel discharge and ballistic separator. Capture velocity per ACGIH IV Manual at 0.5–1.0 m/s for paper and plastic dust, scaling up to 1.0–2.5 m/s for fine shredder discharge.
• Duct velocity: 18–25 m/s in horizontal transport ducts, 22–28 m/s in vertical risers, sized to keep particulate in suspension and avoid settling.
• Dust collector: baghouse with PTFE membrane filter media is standard for paper and plastic dust. Pulse-jet cleaning, dust hopper to rotary airlock and back to material stream where commercially viable, otherwise to a separate disposal bin.
• Explosion protection: NFPA 68 explosion vent panels on the collector, NFPA 69 isolation devices on the inlet duct (rotary airlock, chemical isolation or mechanical valve) to break propagation back to the sorting line.
• Materials: galvanised G90 for the capture and transport ducts. Stainless or polyethylene-lined where moisture is present (glass-crusher exhaust where wash water can entrain).

Dust capture is not just a hygiene asset — it is a productivity asset. Optical sorter performance degrades sharply when paper dust accumulates on the sensor optics. Operators that under-specify dust capture see optical sorter throughput drop 10–20% within months. The capital case for proper dust capture is straightforward: the productivity recovery typically pays back the capture system within two years.

E-waste / WEEE processing HVAC

E-waste is the most technically demanding recycling facility HVAC application. The shredder hood is simultaneously a high-dust-load extraction point and a hazardous gas detection zone for lithium thermal runaway. Downstream metal-recovery processes range from simple eddy-current separation (low HVAC complexity) to acid leaching of printed circuit boards (high HVAC complexity, dedicated stainless duct and chemical scrubber train).

Shredder hood

• Capture velocity: 1.5–2.5 m/s at the shredder discharge, sized to capture both the dust load and any volatile gases from a thermal-runaway event before they migrate to the wider building.
• Gas detection: hydrogen and hydrogen-fluoride detectors at the shredder hood, interlocked to a fast-acting isolation damper, an inert gas knock-down (nitrogen or argon) plumbed into the shredder enclosure, and a process trip.
• Duct material: welded heavy-gauge galvanised or 304 stainless on the hood-to-baghouse run, sized to resist the deflagration pressure pulse upstream of the explosion vent.
• Dust collector: baghouse with NFPA 68 explosion vent panels, NFPA 69 isolation devices, and a fire suppression system (typically water mist or inert gas) as a tertiary defence.

Printed circuit board acid leaching (where present)

• Duct material: 304 or 316L stainless, full welded joints, with provision for periodic acid neutralisation flush cycles.
• Capture: closed enclosure with -25 Pa pressure differential, scrubber-tower discharge.
• Scrubber train: caustic scrubber as primary, polishing scrubber as secondary, with HEPA pre-filter to capture metal-bearing aerosol before the scrubber stages.

Mercury-bearing waste (fluorescent tubes, old LCD backlights)

• Containment: negative-pressure enclosure, sulphur-impregnated activated carbon polishing, dedicated mercury vapour analyser at the stack.
• Duct material: 304 stainless or polyethylene-lined steel.

Note that copper smelting and other high-temperature metal recovery are typically subcontracted off-site to specialist smelters (Nyrstar in Tasmania, various overseas operations) and are not part of the typical Australian e-waste processor's HVAC scope.

Plastic recycling HVAC

Plastic recycling HVAC has three distinct duty zones: shredding, melt extrusion / pelletising, and pellet bagging.

Shredding zone

Mirrors the e-waste shredder pattern at lower hazard intensity (no lithium ignition risk in pure plastic stream, but plastic dust is still NFPA 654 St-1 with Kst typically 50–150 bar.m/s). Galvanised duct, baghouse with explosion vent panels, NFPA 69 isolation. Capture velocity 1.0–2.0 m/s at the shredder.

Melt extrusion zone

Where shredded plastic is melted and extruded into pellets. The melt step releases volatile organic compounds — chain-end fragments, plasticiser residues, and any contaminants from the source material. VOC emissions are particularly significant in mixed-plastic recycling and chemical recycling (pyrolysis) facilities.

• Capture: close-coupled extraction hood at the extruder die, vent header along the cooling water bath.
• Duct material: polyethylene-lined steel or 304 stainless to resist condensing VOC and any acidic decomposition products.
• Treatment: regenerative thermal oxidiser (RTO) or catalytic oxidiser is the dominant Australian solution for VOC destruction. RTO destroys 95–99% of VOC and is the de facto standard for permit compliance.

Pellet bagging zone

• Capture: close-coupled hood at the bagging weigher and the pellet sealing station.
• Duct material: galvanised or 304 stainless with smooth interior to prevent pellet build-up.
• Filter: HEPA H13 final filter to prevent fine pellet fragments from discharging to atmosphere.

Organics composting and FOGO HVAC

Composting halls are among the most aggressive corrosion environments in industrial ventilation. Relative humidity is routinely 90–95%, ammonia concentration can reach hundreds of ppm, and hydrogen sulphide is present in spikes from anaerobic decomposition pockets. Galvanised duct will fail within 24–36 months in a composting hall — the corrosion engineering reality is that you must specify either FRP, polyethylene-lined steel, or 316L stainless for any duct that will see prolonged exposure.

Composting hall HVAC design parameters:

• Air changes per hour: 6–12 ACH for in-vessel composting, lower for windrow operations where buildings are open-sided.
• Negative pressure: -25 to -50 Pa relative to amenity zones.
• Duct material: FRP (fibre-reinforced plastic) is dominant in Australian composting halls — Spirosain, Sintex and similar brands. Polyethylene-lined steel and 316L stainless are alternatives where fire performance requires a non-combustible substrate.
• Odour control: biofilter primary stage (well-suited to organics load) followed by carbon polishing. Acid scrubbing is occasionally added as an ammonia knock-down primary stage for very high ammonia loads.

Anaerobic digestion (AD) plants — typically co-located with FOGO composting — generate biogas (CH4 plus H2S plus CO2). The biogas piping is a hazardous area to AS/NZS 60079 with shutdown interlocks on H2S and CH4 detection. Biogas duct material is 316L stainless or polyethylene-lined steel; carbon steel will fail within months. The biogas is typically combusted in a CHP unit on site, with the CHP exhaust routed through a separate emissions control train.

Hazardous waste HVAC

Hazardous waste covers a wide range of process types, each with a chemical-specific exhaust train. The unifying HVAC characteristics are stainless or FRP duct construction, full welded joints, and dedicated scrubber trains for each chemical class.

Solvent reclamation

Distillation of waste solvent into recovered usable solvent. HVAC fingerprint dominated by VOC vapour control, condenser exhaust and column overhead venting. Duct material: 304 or 316L stainless, RTO or condenser-recovery treatment, hazardous area classification AS/NZS 60079.

Lead-acid battery recycling

Acid mist control on battery breaking, lead dust control on smelting feed preparation. Duct material: FRP or polyethylene-lined steel, sodium hydroxide scrubber for acid mist, baghouse with HEPA polishing for lead dust. Mandatory worker biohazard PPE and air monitoring under SafeWork Australia exposure standards.

Cyanide-bearing waste

Rare in Australian recycling but occurs in goldmine tailings reprocessing. Stainless duct with HCN gas detection and hypochlorite oxidation scrubbing.

Chemical drum cleaning

Triple-rinsed drums for resale or destruction. Wash-water vapour and residual chemical control. Stainless duct, dedicated scrubber by chemical class.

Medical waste autoclave and incinerator HVAC

Australian medical waste is overwhelmingly autoclaved (steam sterilisation at 134 °C) with a small minority of streams (cytotoxic, pathological, anatomical) sent to incineration. The HVAC pattern is autoclave-dominant.

Autoclave area

• Containment: negative-pressure dirty-side loading area, positive-pressure clean-side discharge.
• Exhaust: autoclave cycle exhaust (steam plus condensate plus carry-over), routed through a steam-saturated air handler with HEPA H13 final filtration.
• Duct material: 304 stainless on the autoclave exhaust path due to chronic high-temperature humidity.
• Drain odour: autoclave drain-line vent is a frequent odour complaint source. Vent through dedicated carbon polishing.

Shredder area (post-autoclave)

• Function: render treated waste unrecognisable before landfill or further processing.
• HVAC: capture hood with HEPA H13 final filter, negative pressure, separate from the dirty-side loading containment.

Incinerator (where present)

• Combustion exhaust: separate emissions-control scope (SCR or SNCR for NOx, baghouse plus activated carbon injection for dioxins, scrubber for HCl/SO2).
• Building HVAC: ash handling capture, refractory replacement maintenance dust capture, general building ventilation.
• Duct material: 316L stainless on combustion-side exhaust, galvanised on building-side ventilation.

Combustible dust hazard management — the engineering reality

Combustible dust is the single largest insurance and life-safety driver in recycling facility HVAC design. The framework:

Establishing the hazard

A representative dust sample from the operating waste stream is sent to a lab (in Australia: Fike, IEP Technologies or specialist combustion test laboratories). Three parameters drive the engineering response:

• Kst (deflagration index) — measured in bar.m/s. Paper fibre 50–150 bar.m/s, mixed plastic 50–200 bar.m/s, wood dust often above 200 bar.m/s. Higher Kst means more aggressive deflagration, larger explosion vent area, faster isolation.
• Pmax (maximum deflagration pressure) — typically 7–9 bar absolute for combustible particulate solids. Drives vessel design pressure rating.
• MIE (minimum ignition energy) — drives the assessment of whether static discharge, friction sparking from a metal contaminant, or hot-surface ignition is credible.

Dust class

St-0 (non-explosive), St-1 (Kst 1–200 bar.m/s, weak to moderate), St-2 (Kst 201–300, strong), St-3 (Kst above 300, very strong). Most paper, mixed plastic and organic dust falls in St-1. Wood dust can reach St-2. Metal dust (aluminium, magnesium from C&D or e-waste) can reach St-3.

Engineering response

• Explosion venting (NFPA 68): rupture panels on the collector vessel with a relief path to a safe outdoor location, sized to the vessel volume and Kst. Installed by Rembe, Fike, IEP Technologies or equivalent.
• Explosion isolation (NFPA 69): rotary airlocks, mechanical isolation valves, chemical isolation suppression on the inlet ducting to break propagation back to the process.
• Suppression (NFPA 69): chemical suppression bottles inside the vessel as a tertiary defence where venting alone is insufficient (often used in indoor collectors where venting outdoors is not feasible).
• Inerting (NFPA 69): nitrogen or argon blanket of the vessel headspace to keep oxygen below the limiting oxygen concentration. Used on solvent-bearing dust and lithium-bearing waste streams.

Lithium thermal runaway

Lithium battery thermal runaway is the highest-consequence hazard in modern e-waste and increasingly in MRFs (because consumers improperly dispose lithium cells with kerbside recycling). Thermal runaway releases hydrogen, methane, ethylene, hydrogen fluoride and other volatiles at temperatures of 800–1000 °C — sufficient to ignite the surrounding paper and plastic dust load. The engineering response is layered:

1. Detection: H2 and HF gas detectors at the shredder hood, smoke detection at the conveyor, thermal imaging on the tipping floor.
2. Isolation: fast-acting damper on shredder hood exhaust, rotary airlock on conveyor discharge.
3. Knock-down: nitrogen or argon inerting plumbed into the shredder enclosure, aerosol fire suppression (FK-5-1-12 or equivalent) as a tertiary defence.
4. Containment: explosion-vented baghouse with vent path to safe outdoor location, building HVAC sized to extract any propagating gases without recirculating to occupied zones.

Materials selection by recycling facility zone

The duct material chosen for a recycling facility zone determines its lifetime maintenance cost and its safety performance. The selection rules:

Galvanised steel G90 (Z275)

The default for general building ventilation, kerbside MRF supply and exhaust ducting, sorting line dust transport (dry stream), e-waste building HVAC outside the shredder hot zone, plastic shredding (dry stream), tyre recycling general HVAC, medical waste building HVAC outside the autoclave wet zone. See our companion guide galvanised vs stainless steel duct for full selection criteria.

304 stainless steel

For moderate acid mist exposure (lead-acid battery recycling general areas), e-waste shredder hood (where deflagration pressure pulse resistance is required), autoclave exhaust, mercury vapour control, glass crusher exhaust where moisture is chronic. Mid-range cost, high corrosion resistance.

316L stainless steel

For chemical scrubber discharge, anaerobic digestion biogas paths, chloride-bearing exhaust (some plastic recycling wash-line exhausts), incinerator combustion exhaust, hazardous waste solvent reclamation. Higher cost, very high corrosion resistance, the de facto standard for life-cycle-cost reasons in aggressive zones.

Polyethylene-lined steel

For VOC-heavy plastic recycling extruder exhaust, composting hall exhaust where fire performance requires a non-combustible substrate, hydrogen sulphide bearing biogas paths. Compatible with most acidic and organic chemical loads at temperatures up to 60 °C.

FRP (fibre-reinforced plastic)

For composting hall ductwork (chronic high humidity, ammonia, hydrogen sulphide), AD biogas paths where fire performance is acceptable, scrubber wet-side ducting. Common Australian brands include Spirosain and similar. Light weight, very high corrosion resistance, but combustible — limits use in fire-critical zones.

Worker biohazard protection

Recycling facility workers face significant biohazard exposure. The HVAC system is the primary engineering control between the worker and the contaminant. Key design rules:

Sorting line worker positions

• Local exhaust ventilation: dedicated capture at each sorting position, capture velocity 0.5–1.0 m/s at the breathing zone.
• Cabin pressurisation: for high-hazard sorting (e-waste, medical waste) provide a positive-pressure operator cabin with HEPA H13 supply air.
• PPE complementarity: HVAC engineering is the primary control, P2 or P3 respirators are the personal control overlay.

Medical waste sorting

• Negative-pressure containment: sorting room held at -25 to -50 Pa relative to corridors.
• HEPA H13 final filtration: on all extract paths discharging to atmosphere.
• Anteroom airlocks: on personnel access points to maintain pressure cascade.

Sewage sludge handling

• Dewatering hall ventilation: 6–10 ACH, biofilter or chemical scrubber on extract.
• Worker breathing zone capture: at sludge discharge, conveyor transfer points and storage hoppers.

Soil remediation HVAC

Soil remediation is an emerging Australian recycling discipline driven by brownfield site redevelopment and PFAS contamination management. The dominant treatment technologies are thermal desorption (indirect-fired or direct-fired) and bioremediation, with soil washing used selectively.

Thermal desorption exhaust

• Operating temperature: 200–350 °C indirect-fired, up to 550 °C direct-fired.
• Duct material: high-temperature insulated 304 or 316L stainless steel.
• Treatment: after-burner or thermal oxidiser to destroy residual VOC, baghouse to capture metal-bearing fume, scrubber for acid gas (HCl, SO2).
• Stack: sized against AS 3580 ambient air monitoring positions and EPA approval conditions.

Soil vapour extraction (SVE)

For in-situ remediation. SVE wells draw vapour from the contaminated subsurface, treat it through a granular activated carbon vessel, and discharge through a stack. Duct material is typically galvanised or 304 stainless depending on the contaminant suite.

Bioremediation halls

Active or passive composting of contaminated soil. HVAC fingerprint mirrors organics composting — high humidity, ammonia, biofilter on extract.

SBKJ machinery for recycling facility HVAC duct fabrication

Australian fabricators serving recycling facility projects need machinery that handles the full material range — galvanised G90 for general work, 304 and 316L stainless for chemical exposure zones — and that delivers the leak class required for negative-pressure odour control duct. SBKJ machine selection by recycling facility duty:

SBAL-V auto duct line

For galvanised rectangular duct on general MRF supply and exhaust, sorting line dust capture transport, and tipping floor extract. Single-shift output 800–1,200 m². Integral TDF flange formation gives the tight-leakage performance needed for negative-pressure odour control duct. See auto duct lines category and our auto duct line buyer's guide for full specifications.

SBTF spiral tubeformer

For round duct on return-air paths, dust transport (where round duct geometry is preferred for flow), and stack risers. Output rates 80–150 m per shift depending on diameter. See spiral tubeformer category.

TDF flange former

Standalone flange formation where rectangular duct is fabricated by hand methods and only the flange is machine-formed. Used by smaller fabricators servicing brownfield retrofit projects where shop space precludes a full auto duct line.

Stainless variants

SBAL-V auto duct line and SBTF spiral tubeformer are both available in stainless-steel-capable variants for fabricators servicing chemical scrubber discharge, AD biogas paths, autoclave exhaust and acid leaching exhaust. Stainless capability requires upgraded tooling, separate tooling sets to prevent galvanic contamination, and adjusted forming pressures.

Comparison with adjacent verticals

Recycling facility HVAC fabrication overlaps with several other industrial verticals SBKJ supports — see our food processing and cold chain industry guides for HVAC patterns that share materials and leak class requirements with recycling work, and our mining ventilation and battery gigafactory guides for adjacent dust hazard and explosion protection scenarios.

Construction phasing for a greenfield Australian MRF

The construction sequence for a 100,000–250,000 tonne per annum Australian MRF, as we have seen on multiple projects supplied by SBKJ-equipped fabricators:

Stage 1 — Tipping floor and odour scrubber inlet (weeks 1–8)

Structural concrete pour, building shell, tipping floor capture hood installation, primary odour scrubber inlet ducting. Duct fabrication is typically 60% of total project duct volume in this stage.

Stage 2 — Sorting line dust capture (weeks 6–12)

Sorting line equipment installation in parallel with capture hood installation, baghouse foundation, transport ducting from each capture point to the baghouse manifold. Duct fabrication 25% of total volume.

Stage 3 — Shredder hood and explosion-isolated baghouse (weeks 10–14)

Shredder installation, hood-to-baghouse ducting, explosion vent panel installation, NFPA 69 isolation device installation, gas detector installation. Duct fabrication 10% of total volume but high complexity per metre.

Stage 4 — BMS commissioning and balancing (weeks 14–18)

Building management system commissioning, fan VFD tuning, damper position calibration, smoke-test capture verification at every hood, pressure cascade verification. Duct fabrication is complete; the work is verification.

Stage 5 — Performance testing and handover (weeks 18–22)

Full-load performance testing, EPA boundary monitoring verification, dust collector pressure-drop baseline, explosion vent rupture-disc inspection, handover documentation. Final 5% of duct fabrication addresses retrofit changes identified during commissioning.

Brownfield retrofit projects — adding capacity to an existing operating MRF — run on a different sequence because work is constrained to the operator's shutdown windows. Major Australian MRFs typically allow only Christmas (1 week) and Easter (4 days) for shutdown. Brownfield retrofits therefore run as a series of phased shutdowns over 12–24 months, with as much pre-fabrication as possible done off-site to minimise on-site shutdown time. SBKJ-equipped fabricators producing to AS/NZS 4254 with TDF flange tolerances have a structural advantage on brownfield retrofit work because the pre-fabricated sections install quickly with minimal field rework.

Australian project lead times and budget reference points

Greenfield Australian MRF HVAC ductwork typically runs 16–24 weeks from approved drawings to handover for a 100,000–250,000 tonne per annum facility. The critical path items:

• Dust collector and explosion protection skid: 12–16 weeks lead from order. NFPA 68 vent panels are typically European-sourced with 8–12 week ex-works lead.
• Odour scrubber package: 10–14 weeks lead from order. Australian specialist suppliers (Industroquip, Anguil, ERG APC and parallel European brands) dominate this segment.
• Duct fabrication: runs in parallel. SBKJ-equipped Australian fabricator producing 800–1,200 m² per shift on an SBAL-V can fabricate a typical MRF project's duct in 4–6 shifts of dedicated production.
• Stainless duct: longer lead than galvanised due to material availability and lower fabrication throughput. Typical 6–10 weeks for stainless sections.
• FRP ductwork: 8–12 weeks lead, typically Australian-fabricated.

Budget reference points (excluding GST, indicative for 2026):

• Greenfield 150,000 tpa MRF HVAC duct package: AUD 2.5–4.0 million for the duct fabrication and installation scope, exclusive of dust collector, scrubber package and BMS.
• Composting hall HVAC retrofit (10,000 tpa): AUD 800,000–1.5 million.
• E-waste shredder hood and baghouse retrofit: AUD 1.0–2.5 million depending on explosion protection complexity.
• Anaerobic digestion biogas duct package: AUD 600,000–1.5 million depending on scale.

SBKJ machinery purchase economics for an Australian fabricator entering this vertical: an SBAL-V auto duct line plus SBTF spiral tubeformer plus stainless tooling upgrades typically pays back within 18–24 months on a fabricator with a single major recycling project commitment, given recycling facility duct premium pricing relative to commercial HVAC.

How SBKJ supports Australian recycling facility projects

SBKJ Group operates from Box Hill North in Melbourne with full Australian after-sales coverage, including the recycling and waste sorting segment. The pattern of support we provide:

• Engineering review: we walk fabricators through the auto duct line specification matched to the facility type. A pure MRF fabricator needs different tooling configuration from a fabricator servicing AD biogas and chemical scrubber discharge work.
• AS/NZS 4254 calibration: all SBKJ machinery shipped to Australia is configured to AS/NZS 4254 dimensional and tolerance specifications by default. SMACNA and EN 1505 configurations are available on request.
• Stainless tooling sets: separate tooling sets prevent galvanic contamination between galvanised and stainless production runs. Critical for fabricators servicing chemical scrubber and AD biogas duct work.
• TDF flange precision: our integral TDF flange formers achieve leak class A or B per AS/NZS 4254 — necessary for negative-pressure odour control duct that must hold -25 to -50 Pa with low leak rate.
• Australian-resident commissioning: SBKJ engineers based in Box Hill North handle commissioning and after-sales without the visa and timezone friction of overseas-only support.
• Spare parts continuity: 10-year parts availability commitment in writing, addressing the long-tail concern for fabricators making a generational machinery investment.

See our Australia regional page for the full local-support model and our contact page for an engineer-led specification call on your specific recycling facility project.

FAQ

What is the most dangerous dust in a recycling facility from an explosion standpoint?

Paper fibre dust and shredded plastic dust both fall under NFPA 484 / 654 combustible particulate solids and are typically classified St-1 with Kst values 50–200 bar.m/s. Wood dust from C&D processing is more aggressive with Kst values commonly above 200 bar.m/s. The highest-consequence hazard in a modern Australian MRF is not actually dust ignition but lithium battery thermal runaway from improperly sorted e-waste cells, which can ignite the surrounding paper and plastic dust load and create a secondary deflagration. Every recycling facility HVAC design must address both ignition sources together.

How many air changes per hour are required on a tipping floor?

AS 1668.2 does not prescribe a specific tipping-floor air change rate but most Australian MRF designs target 4–8 ACH minimum for general ventilation, with localised capture at the tip face designed to ACGIH IV Manual capture velocities — typically 0.5–1.0 m/s at the breathing zone for paper and plastic dust. Tipping floors handling MSW with significant organic load run higher rates of 6–10 ACH and are kept under negative pressure relative to office and amenity zones to contain odour.

What duct material should I specify for a Materials Recovery Facility?

Galvanised steel to G90 / Z275 coating class is the default for general MRF supply and exhaust ducting because it is cost-effective and corrosion-resistant in a moderately humid environment. Switch to 304 stainless where there is acid mist (lead-acid battery recycling, certain e-waste leaching processes) or chronic high humidity such as composting halls. 316L stainless is used in chemical scrubber discharge ductwork and where chloride exposure is unavoidable. Polyethylene-lined or solid FRP is appropriate for VOC-heavy plastic recycling extruder exhaust and aggressive organics paths.

How is lithium battery thermal runaway managed in HVAC duct design?

Lithium thermal runaway in shredded e-waste releases hydrogen, methane, ethylene and hydrogen fluoride at high temperature. The HVAC duct response has three layers: gas detection at the shredder hood with H2 and HF sensors interlocked to a fast-acting damper isolation; explosion vent panels on the connected baghouse rated to NFPA 68 with the relief path directed to a safe outdoor location; and inert gas knock-down (typically nitrogen or argon) plumbed into the shredder enclosure. Duct material between the shredder hood and the explosion-isolated baghouse should be welded stainless or sufficiently heavy-gauge galvanised to resist a deflagration pressure pulse.

Do Australian MRFs really need NFPA-grade dust hazard analysis given AS 4655 exists?

AS 4655 covers dust collection equipment performance and AS/NZS 4360 risk management framework underpins the DHA approach, but Australian recycling operators routinely specify NFPA 484 for combustible metals and NFPA 654 for industrial particulate solids because they are the most detailed prescriptive standards in the world for combustible dust. Major operators such as Cleanaway, Veolia and Visy typically engage a fire engineer to deliver a Dust Hazard Analysis to AS/NZS 4360 framework using NFPA 654 as the technical reference, which then drives explosion vent sizing per NFPA 68 and isolation per NFPA 69.

What odour control technology fits an MRF tipping floor?

Three technologies dominate Australian MRF tipping-floor odour control: activated carbon scrubbers for low-concentration mixed VOC and sulphide loads typical of kerbside MRFs; biofilters for FOGO and organics-heavy streams where the odour is biologically degradable; and chemical scrubbers (caustic, sodium hypochlorite or hydrogen peroxide) for higher concentrations and hydrogen sulphide spikes. Many large operators run a two-stage train — chemical scrubber as primary load knock-down followed by carbon polishing — discharging through a tall stack designed against AS 3580 air quality monitoring positions and EPA approval conditions.

What is the typical lead time for a recycling facility HVAC duct project?

Greenfield Australian MRF HVAC ductwork typically runs 16–24 weeks from approved drawings to handover for a 100,000–250,000 tpa facility. Critical path is usually the dust collector and explosion protection skid (12–16 weeks lead) and the odour scrubber package (10–14 weeks). Duct fabrication runs in parallel — SBKJ machinery installed in an Australian fabrication shop will produce 800–1,200 m² per shift on an SBAL-V auto duct line. Brownfield retrofits inside an operating MRF run longer because work is sequenced around facility shutdown windows, which tend to be only Christmas and Easter for major Australian operators.

How did the 2018 international import restrictions affect Australian recycling facility design today?

The 2018 import restrictions on mixed paper and contaminated plastic ended Australia's ability to ship low-grade kerbside recycling offshore. The federal Recycling Modernisation Fund (~AUD 250M) plus matched state funding has driven a wave of domestic MRF, plastic recycling and FOGO facility construction since 2020. New Australian recycling facilities are being built to higher specifications — better dust capture, better odour control, more rigorous explosion protection — because they must produce export-grade or domestic-feedstock-grade output rather than baled mixed material. SBKJ has supplied auto duct line machinery to Australian fabricators servicing exactly these projects, and demand through 2026 remains strong as state EPAs progressively raise resource recovery targets.

Get an SBKJ engineer quote for your recycling facility duct fabrication setup →