One of the key principles of the circular economy is extending product lifetimes with aim to slow down material turnover rates and thus reduce resource consumption and emissions. A recent study by Lasting PhD candidate Kamila Krych and her colleagues from NTNU, Daniel B. Müller and Johan B. Pettersen, introduces an innovative Python-based tool that enhances the way we model product lifetimes in dynamic material flow analysis (dMFA). This breakthrough allows for a deeper understanding of both inherent product durability (“nature”) and external interventions like repairs and consumer behavior (“nurture”).
Traditionally, dMFA assigns fixed lifetimes to products at their inception, overlooking the influence of nurture-focused strategies such as repair subsidies or spare parts availability. The new tool addresses this gap by dynamically incorporating age, period, and cohort effects through the hazard function, which connects outflows to preceding stock levels. Compatible with the Open Dynamic Material Systems Model (ODYM) framework, this tool opens new opportunities for analyzing real-world scenarios in circular economy research.
Case Study: Dishwashers in Norway
The study applied the tool to dishwashers in Norway, testing five scenarios. All scenarios assume a lifetime improvement of 20%, yet each scenario affects a different share of dishwashers, yielding different results.
- Baseline Scenario: No additional lifetime extension measures.
- Lifespan Labelling: Durability labels on new dishwashers guide consumers toward longer-lasting products (a cohort-based strategy).
- Repair Subsidies: Financial incentives lower repair costs, encouraging consumers to repair rather than replace appliances (a period-based strategy).
- Spare Parts Accessibility: Regulations extend the availability and affordability of spare parts, improving repair feasibility (age and cohort interaction).
- Guarantee Awareness: Campaigns to increase awareness of existing 5-year guarantees encourage maintenance and longevity (interaction between age and period effects, focused on younger products).
The findings highlight that repair subsidies (scenario 2) had the fastest and largest impact, reducing sales of new dishwashers by 16% by 2050. This reflects the scenario’s ability to impact products already in use, offering a broader reach than cohort-based strategies. This was followed by lifespan labeling (scenario 1), which took longer to impact because it only affects new products entering the stock, but ultimately achieved the same reduction. Spare Parts Accessibility (Scenario 3) and Guarantee Awareness (Scenario 4) showed smaller impacts (6% and 2% reductions, respectively) due to their limited reach or focus on younger appliances with lower failure rates.
Implications for Policy and Research
This tool has significant implications for policy and research, particularly in shaping the European Union’s ongoing push for a “right-to-repair” framework and other life-extension initiatives. By explicitly modeling nurture-related factors, the tool enables stakeholders—beyond just producers and designers—to participate in extending product lifetimes. Consumers, repairers, resellers, and policymakers all have roles to play, whether through campaigns, financial incentives, or enhanced access to repair services.
Moreover, the tool opens new avenues for exploring business models centered on life extension, such as leasing or refurbishing, which depend on nurture-focused interventions. As the circular economy evolves, the ability to dynamically model these interactions will be critical for designing effective, data-driven strategies.
Driving Lasting Impact
This research, conducted as part of the Lasting project, represents a significant advancement in dynamic material flow analysis (dMFA) methodologies. By integrating product “nurture” into dMFA, the study introduces a robust framework that captures the interplay of age, period, and cohort effects, enabling a more comprehensive evaluation of strategies to extend product lifetimes.
From durability labeling to repair subsidies, the findings highlight that the most impactful measures address all stages of a product’s lifecycle. Such tools are invaluable as policies and consumer behaviors increasingly prioritize sustainability, supporting smoother transitions to a circular economy. For researchers and policymakers, this work offers a strong foundation for designing and testing life-extension strategies, predicting their impacts, and advancing efforts to reduce resource use and emissions on a global scale.
Reference
Krych, K., Müller, D. B., & Pettersen, J. B. (2024) The “nature” and “nurture” of product lifetimes in dynamic stock modeling. Journal of Industrial Ecology. 1–13. https://doi.org/10.1111/jiec.13586