A correction has been made to section 2 Methods, 2.1 System dynamics modeling approach, Paragraph 1. The numerical integration time step was incorrect. The corrected paragraph appears below:
“System dynamics represent complex systems such as stocks (accumulations) and flows (rates) governed by feedback loops and time delays (Meadows, 2008; Nemet, 2006). Pioneered by Forrester (1961) for industrial management, this methodology suits circular economy systems characterized by feedback dominance, time delays, nonlinear relationships, and policy resistance (Rubin et al., 2015; Brooks et al., 2018). We developed the model using Vensim PLE Plus, operating on six-weekly time steps (Δt = 0.125 years) from 2015 to 2040. The quarterly timestep originally used (Δt = 0.25 years) produced Euler integration instability in the Program Viability feedback loop; halving the time step eliminates this numerical artefact while maintaining computational efficiency and is consistent with best practice for models with fast feedback loops (Sterman, 2000). The model employs EPR Implementation Level at zero throughout 2015–2024, reflecting the voluntary APCO framework under which no mandatory producer fees existed, with EPR activating as a scenario lever from 2025 onward (Homer, 1996).”
The reference for Homer, 1996 was missing. The reference is Homer, J. B. (1996). Why we iterate: scientific modeling in theory and practice. System Dynamics Review, 12(1), 1–19.
A correction has been made to section 2 Methods, 2.2 Material Flow with enhanced narrative, “2.2.1 Membrane recycling technology specification,” Paragraph 5. The initial stock values and 2025 consumption anchors for rigid packaging were based on total packaging figures rather than rigid-only figures. The corrected paragraph appears below:
“Rigid plastic packaging stocks initialize at 108,750 tonnes in 2015, representing in-market material with approximately 3-month average residence time. Annual consumption comprises 86% business-to-consumer applications (primarily beverage bottles, food containers, household product packaging) and 14% business-to-business applications (transport packaging, industrial containers). Consumption grows endogenously at 2.84% annually for B2C and 2.71% for B2B, driven by population growth (1.5% annually), economic expansion (GDP growth averaging 2.5%), and per capita consumption increases (0.3%–0.8% annually) observed in historical APFF data, reaching 576,000 tonnes/year. This value reflects APFF 2022–23 data showing rigid plastics account for approximately 40% of total plastic packaging. Collection rates begin at 35% baseline under conventional kerbside systems, representing the weighted average across Australian jurisdictions before CDS implementation. However, the model allows this to increase dramatically—potentially reaching 70%—when container-deposit schemes achieve universal coverage, reflecting empirical evidence from NSW (2017–2023) and Queensland (2018), where beverage container return rates exceeded 72% within 2 years of the scheme’s implementation.”
A correction has been made to section 2 Methods, 2.2 Material flow structure with enhanced narrative, “2.2.1 Membrane recycling technology specification,” Paragraph 7. The initial stock value and 2025 consumption anchor for flexible packaging required correction. The corrected paragraph appears below:
“Flexible plastic packaging stocks initialized at 164,250 tonnes in 2015, representing in-market material with approximately 3-month average residence time. Annual consumption comprises 79% business-to-consumer applications (food wrap, shopping bags, bread bags, and frozen food pouches) and 21% business-to-business applications (pallet wrap, shipping envelopes, and protective packaging). Consumption grew at 2.84% B2C and 2.71% B2B annually, reaching 870,000 tonnes/year, representing approximately 60% of total plastic packaging per APFF 2022–23. Growth rates match rigid plastics but can be reduced substantially—potentially to near-zero or negative—through elimination mandates that target unnecessary formats. Base collection rates start at just 0.5% under conventional kerbside (most MRFs reject flexible plastics due to equipment incompatibility), increasing to maximum 5% even with full EPR support, as flexible plastics remain incompatible with CDS beverage return infrastructure.”
A correction has been made to section 2 Methods, 2.2 Material flow structure with enhanced narrative, “2.2.1 Membrane recycling technology specification,” Paragraph 8. The recyclate value parameter and processing economics description required correction to reflect current Australian market prices. The corrected paragraph appears below:
“Processing economics for flexible plastics prove catastrophically unviable: membrane-enhanced processing costs approximately $19,500 per tonne, comprising collection ($150/t), specialized sorting ($800/t), solvent dissolution ($5,000/t), membrane-filtration modules ($4,500/t), solvent-recovery systems ($3,500/t), precipitation and drying ($2,800/t), membrane replacement ($1,500/t), and quality assurance ($1,250/t). Recyclate values remain $600 per tonne—identical to mechanical recyclate—as the mixed-plastic composition limits application to low-value downcycling uses. This reflects blended rigid plastic recyclate prices 2023–24 (PET $520–735/t, HDPE $855–1,000/t, mixed kerbside $200–400/t; source: APFF, 2023–24). At $600/tonne recyclate value and 75% recovery rate, revenue per tonne processed is $450/tonne against a processing cost of $800/tonne, generating a net loss of approximately $290/tonne under current market conditions. These catastrophic economics activate Loop B4 (diminishing returns), the master constraint that prevents high recovery rates through universal processing approaches.”
A correction has been made to the section 2 Methods, 2.5 Data sources and validation, Paragraph 1. The Virgin PET price used as a constant throughout the simulation was inconsistent with actual market conditions. The corrected paragraph appears below:
“Material flow data derives from Australian Plastics Flows and Fates (APFF) annual reports 2015–2024, conducted by DCEEW with Blue Environment data collection (APCO, 2022; APCO, 2024; European Commission, 2019). APCO Packaging Consumption Data 2017–2023 provide consumption disaggregation (ICIS, 2025; EFSA, 2018). Economic parameters reflect Australian market conditions: mechanical costs ($800/t) from Blue Environment analysis (Rahimi and García, 2017), membrane costs ($19,500/t) from closed-loop partners and APK AG assessments (Material Economics, 2018; Forrester, 1961), elimination costs ($130/t) from European Commission impact assessments (APCO, 2023), virgin PET pricing (approximately $1,000/t in 2015, $750/t in 2020 [COVID demand collapse], $1,400/t in 2021–22 (energy crisis peak), and $850–900/t by 2025–26) from ICIS market data, 2024–26, and food-grade premium (30%) from EFSA recycling opinions and Closed Loop Foundation market analysis (Blue Environment, 2021; Kaiser et al., 2018). Technical parameters, including learning rates (membrane 25%, mechanical 15%), derive from Nemet and Rubin meta-analyses of environmental technology deployments (Staub, 2018; APCO, 2018). Recovery rates (mechanical 75%, membrane 85% clean/60% contaminated) reflect vendor specifications and pilot demonstrations (Closed Loop Partners, 2020; APK, 2020).”
A correction has been made to the section 3 Results, 3.1 Historical validation (2015–2024), Paragraph 1. A methodological note on recovery rate calculation is required. The corrected paragraph appears below:
“The model successfully reproduced nine years of Australian plastic packaging system behavior. Note on recovery rate methodology: the model’s current recovery rate is calculated as total material recovered divided by total packaging end-of-life (including both rigid and flexible streams), producing values of approximately 10–15% compared to APFF’s reported 16–26%. This reflects a genuine methodological distinction—the model denominator includes flexible plastics with near-zero recovery rates, whereas APFF reporting uses broader packaging categories and includes energy recovery. Separate rigid recovery rate (approximately 25–38%, rising through CDS expansion) and flexible recovery rate (approximately 0.5–1.4%, with voluntary peak in 2022 followed by collapse) provide the primary material-specific validation outputs. The trajectory shape—gradual improvement through CDS expansion, peak around 2021–22, sharp decline post-REDcycle collapse, stabilisation 2023–24—constitutes valid structural validation.”
A correction has been made to the section 3 Results, 3.1 Historical validation (2015–2024), Paragraph 3. The corrected paragraph appears below:
“Critically, the REDcycle collapse emerged endogenously from fiscal pressure accumulation under the voluntary funding regime. With EPR Implementation Level at zero throughout 2015–2024, available funding was constrained to public allocations of approximately $80M/year. As voluntary flexible collection programs scaled from zero to approximately 8,400 tonnes/year during 2019–2022, net processing losses accumulated at approximately $18,700/tonne, generating voluntary program net loss of approximately $160–170M/year at peak—more than double available funding. Perceived fiscal pressure, smoothed with a 0.75-year organisational response delay representing the lag between financial stress and program closure, crossed the program viability threshold approximately consistent with the November 2022 REDcycle closure timing. The model reproduced the post-collapse recovery rate decline without any exogenous shock representing the REDcycle event, validating the fiscal constraint hypothesis.”
A correction has been made to the section 3 Results, 3.2 Scenario analysis results (2025–2040), Paragraph 4. The savings figure for Scenario 4 used an incorrect counterfactual. The corrected paragraph appears below:
“Scenario 4 (“optimal 80/15/5 strategy”) succeeds dramatically, achieving 68% recovery (97% of target) at $510M annually—2.3-times cheaper than Scenario 3 while delivering 11 percentage points higher performance. Effective recovery including elimination reaches 72%–75% when accounting for 641,000 tonnes/year of eliminated formats. Fiscal pressure of 0.89 indicates sustainable funding balance. Marginal costs remain moderate at $22M per percentage point, enabling continued incremental improvements. The scenario eliminates 80% of unnecessary flexible formats, saving approximately $77M annually in avoided landfill costs while incurring $83M elimination expenses — approximately cost-neutral versus landfill, but substantially cheaper than the $12.4B that membrane processing of the same volumes would require. Focused membrane deployment of 52,000 tonnes/year (6.5% of total EoL) for essential medical and pharmaceutical applications achieves 77% capacity utilization, thus activating learning curves and quality premiums. Mechanical processing expands to 600,000 tonnes/year for rigid plastics, operating at 82% utilization with positive economics. This strategic allocation maximizes system efficiency by matching technologies to economically viable material streams.”
A correction has been made to the section 4 Discussion, 4.1 The rigid–flexible divide is fundamental, not transitional, Paragraph 2. The description of rigid plastics recycling economics required updating to reflect corrected market prices. The corrected paragraph below:
“This physical reality drives policy implications. At corrected Australian market prices (blended recyclate value $600/tonne, processing cost $800/tonne, 75% recovery rate), mechanical recycling of rigid plastics generates a net loss of approximately $290/tonne, consistent with APFF (2023–24) findings that recovery costs exceed virgin material value under current market conditions. EPR support is therefore required to sustain rigid plastics recycling — reinforcing the paper’s policy argument for mandatory EPR frameworks. Despite this, rigid plastics exhibit substantially superior economics to flexible plastics ($290/t loss versus $18,700/t loss) and justify processing-focused investments activating Loops R1–R3 (quality premiums, scale economies, feedstock quality improvements). Materials exhibiting catastrophic economics (flexible plastics: $18,700/t loss) justify elimination-focused interventions, where $130/t in elimination costs provide 150:1 cost–benefit ratios versus processing alternatives. Treating all plastics homogeneously—the implicit assumption underlying Australia’s 70% target and EU recycling mandates—creates economically irrational policy that mixes high-return and catastrophically negative-return interventions.”
A correction has been made to the section 4 Discussion, 4.3 Elimination economics: 150:1 cost–benefit ratio, Paragraph 1. The benefit-cost ratio used an incorrect counterfactual. Eliminated packaging would have been landfilled, not membrane-processed. The corrected paragraph appears below:
“Eliminating unnecessary flexible packaging costs $130/tonne, encompassing industry reformulation ($45/t), alternative packaging development ($35/t), supply chain adaptation ($25/t), regulatory compliance ($15/t), and enforcement ($10/t). Australian landfill gate fees average approximately $150–250/tonne. The three-way comparison is: elimination $130/t, landfill $150–250/t, membrane processing $19,500/t. Elimination therefore provides approximately a 2:1 cost advantage over the landfill counterfactual, and 150:1 versus membrane processing—the latter figure being relevant only for the 5% of essential formats that genuinely require advanced recycling. The avoided cost versus landfill is approximately 641,000 t/yr × ($250 − $130)/t = $77M/year.”
A correction has been made to the section 4 Discussion, 4.4 Voluntary approaches: systematic failure mechanisms, Paragraph 1. The explanation of voluntary failure mechanisms was incomplete. The corrected paragraph appears below:
“Eight years of Australian experience (2016–2024) achieving four percentage points improvement despite $690M of investment demonstrates structural failures in a voluntary approach. Two complementary mechanisms explain systematic voluntary failure. Loop B3 (Policy Uncertainty) identifies how voluntary frameworks require continuous multi-stakeholder negotiation generating regulatory complexity and persistent uncertainty. A fiscal mechanism compounds this: with EPR implementation level at zero throughout 2015–2024, available funding was constrained to approximately $80M/year. Voluntary programs like REDcycle faced an unavoidable fiscal trap—at $18,700/tonne processing losses, any program exceeding approximately 4,000 tonnes/year generated losses exceeding total available public funding. The REDcycle collapse is therefore a structural inevitability of attempting subsidised flexible plastic collection without mandatory funding. The Australian Packaging Covenant involved more than 500 organizations across 12 working groups to produce 47 technical specifications with annual adjustments, thus creating process complexity without policy certainty. Investment decisions requiring 10–15 years payback periods cannot proceed under conditions of annual specification changes and voluntary commitment unpredictability.”
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“The author(s) declared that generative AI was used in the creation of this manuscript. The author used AI-assisted tools (Claude, Anthropic) during model development and analysis, including equation validation, unit consistency checking, and structural reasoning. AI assistance was not used to generate the manuscript text. All intellectual contributions, interpretive claims, and conclusions are the author’s own.
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Summary
Keywords
Australia, circular economy, extended producer responsibility, membrane technology, plastic packaging, policy analysis, system dynamics
Citation
Melles G (2026) Correction: System dynamics modeling of membrane technology deployment in Australia. Front. Membr. Sci. Technol. 5:1892157. doi: 10.3389/frmst.2026.1892157
Received
27 May 2026
Revised
31 May 2026
Accepted
03 June 2026
Published
09 July 2026
Volume
5 - 2026
Edited and reviewed by
Hamidreza Mahdavi, Monash University, Australia
Updates
Copyright
© 2026 Melles.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Gavin Melles, gmelles@swin.edu.au
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.