Transitioning to Sustainable Consumer Food Behaviours: Leveraging Retailer Infrastructure and Advancing Household Food Waste Measurement
EMBARGOED UNTIL 2028-07-11
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2025
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Doctoral Thesis
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EMBARGOED UNTIL 2028-07-11
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Abstract
The global food system has undergone profound changes due to industrialisation, modernisation, and globalisation, leading to increased agricultural productivity, improved food availability, and enhanced global nutrition. Mechanised farming, synthetic fertilisers, and food preservation techniques have transformed food production, enabling the creation of interconnected global supply chains and reducing reliance on human labour. While these advances have supported economic and population growth, this transformation has also led to significant environmental challenges. The food system now accounts for about one-quarter of global greenhouse gas emissions (GHGE), as well as extensive water pollution and land use. Two key consumer behaviours — dietary choices and food waste — strongly influence the sustainability of the food system. The rise of Western diets, rich in animal products and highly processed foods, has contributed to both environmental degradation and the global increase in non-communicable diseases. Livestock farming accounts for over 50% of the GHGE from the food system, with high consumption of animal products in developed countries significantly driving GHGE and resource depletion. Food waste is a critical environmental challenge, with households accounting for approximately 60% of the total waste. This is particularly prevalent in high- and medium-income countries, where households are the largest contributors to food waste. The environmental impact of avoidable food waste is irreversible, as the resources used in its production, processing, and distribution cannot be recovered. This issue is further exacerbated by methane emissions from decomposing food in landfills, which contribute to climate change. Addressing these behaviours is therefore essential for enhancing the sustainability of the food system. Changing consumer food behaviours presents significant challenges due to the complex interplay of cultural, social, and economic influences that shape dietary preferences. These factors make large-scale behaviour change difficult to achieve. General dietary guidelines, such as promoting the reduction of animal product consumption in favour of plant-based foods, often lack the specificity and actionable steps necessary to effectively drive behaviour change. Additionally, consumer behaviours related to food planning, shopping, and stockpiling are strongly associated with food waste. Psychological and social factors, such as the ``good provider'' identity, the desire to minimise inconvenience, lack of prioritisation, and perceived exemption from responsibility, further complicate efforts to reduce food waste. This thesis has two primary objectives. The first is to investigate how retailers and their infrastructure can be leveraged to promote sustainable food choices, particularly by reducing animal product consumption. As key intermediaries between consumers and products, retailers are uniquely positioned to influence purchasing decisions by intervening at the point of purchase. Behavioural nudges are particularly well-suited for retail environments due to their low implementation costs and non-invasive nature, and they are already widely used in store design, product placement, and promotions. The digitalisation of retail environments further enhances opportunities for food behaviour interventions. Online grocery platforms and retailer loyalty programs generate vast amounts of consumer-specific purchase data, which can be used to develop personally relevant interventions. Moreover, digital interfaces allow for the delivery of highly specific and actionable product recommendations at the precise moment when consumers make their purchasing decisions. The second objective addresses household food waste. While retailer infrastructure could also facilitate interventions to reduce food waste, the lack of accurate methods for measuring household food waste limits the ability to evaluate intervention effectiveness. As such, this objective focuses on identifying barriers to reliable food waste measurement and exploring potential strategies to enhance its accuracy. The thesis is composed of four articles addressing these research objectives. The first article leverages household loyalty program data to assess the GHGE reduction potential of specific, actionable, and personally relevant product swap recommendations targeting high-impact food items. Simulations on 347 households show that replacing a single animal-based product with a plant-based alternative per shopping trip could reduce the GHGE of food purchases by an average of 26%, achieving two-thirds of the reductions possible if all animal-based products were substituted. Building on these findings, the second article employs an online supermarket experiment to evaluate the effectiveness of specific and actionable product recommendations. A 2×2 factorial randomised controlled trial (n=1,059) further examines whether targeted product swap recommendations and GHGE reduction information enhance climate-friendly shopping behaviours. Results indicate that consumers are receptive to product swap recommendations, with nearly 90% opting to swap at least one product, leading to an average basket emissions reduction of 25%. For most consumers, simply providing specific and actionable swap options is sufficient to encourage climate-friendlier choices, even in the absence of GHGE reduction information or targeted recommendations. However, exploratory analyses amongst high meat consumers - who exhibit higher basket GHGE and lower initial willingness to change — reveal that GHGE reduction information can significantly enhance the effectiveness of product swap recommendations for this subgroup, leading to greater GHGE reductions and higher self-efficacy to reduce animal product consumption. The third article presents a large-scale field experiment (n=359 households) that compares the accuracy of common household food waste measurement methods and examines barriers to reliable food waste estimates. Findings indicate that physical waste audits provide the most accurate estimates, while self-reported methods systematically underestimate waste levels. The study also offers empirical evidence of the Hawthorne effect in food waste measurement, showing that participants unaware of the study's focus on food waste generated higher levels of waste. Building on these insights, the article provides a decision-aid tool to guide researchers in selecting the most appropriate measurement method based on study objectives and best practices for implementation. The fourth article examines systemic challenges in household food waste measurement, particularly issues of accuracy and replicability. These challenges stem from ambiguous definitions, methodological weaknesses, and the absence of standardised approaches. The article explores how an open-source principled framework — built on community collaboration, transparency, iterative development, and meritocracy — can enhance the development and application of household food waste measurement methods, addressing these core challenges and improving the reliability of food waste estimates. In summary, this thesis highlights the significant potential of leveraging retailers and their infrastructure to promote sustainable consumer food behaviours. Retailers are uniquely positioned to encourage more sustainable choices at the point of purchase, with specific and actionable product swap recommendations emerging as an effective strategy for reducing dietary GHGE. Furthermore, retailers could play a crucial role in mitigating household food waste by using similar recommendations to address purchasing behaviours that contribute to waste, such as buying excessive quantities. However, the limitations of existing food waste measurement methods currently hinder the accurate evaluation of such interventions. Advancing household food waste measurement to be capable of long-term, incognisant, accurate monitoring is essential for this next step. By supporting behaviour change mechanisms to address both high animal product consumption and household food waste, retailers have the potential to become key drivers of sustainable consumer food behaviours.
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ETH Zurich
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Global food system; Food sustainability; Greenhouse gas emissions
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03681 - Fleisch, Elgar / Fleisch, Elgar
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197633 - ShopHero - Digital Receipt Based Sustainability and Food Waste Monitoring and Interventions (SNF)