Curbing household food waste and associated climate change impacts in an ageing society

Food production and consumption significantly impact global environmental sustainability. Life cycle assessments (LCA) reveal that the food chain accounts for over one-third of global greenhouse gas (GHG) emissions, and food loss and waste contribute to approximately half of these emissions. Minimizing food waste is crucial for both food security and environmental sustainability. In Japan, a significant portion of food waste originates from households, and the government aims to reduce this by 50% from 2000 levels by 2030. This study investigates the structure of household food waste (FW) and its associated life cycle GHG emissions (FWGHG) in Japan, considering varying consumption patterns across different age groups of household heads. Japan's rapidly aging population makes this analysis particularly relevant, as demographic shifts influence food-related GHG emissions. The study defines household FW as edible food directly discarded by households and FWGHG as emissions from cradle to retail. The findings aim to inform policy strategies for reducing food waste and emissions, considering diverse consumption patterns and future demographic trends.

Existing research highlights the substantial environmental impact of food production and consumption, with food loss and waste contributing significantly to global GHG emissions. Studies using LCA have quantified the GHG emissions associated with various stages of the food supply chain, emphasizing the need for waste reduction. Several studies have examined food waste in different countries, revealing varying per capita waste levels and contributing factors. Research on the impact of demographic changes on food consumption and emissions has shown a correlation between aging populations and altered dietary habits. However, the specific relationship between household food waste, age, and GHG emissions in Japan, a country with a rapidly aging population and high reliance on food imports, requires further investigation. This study addresses this gap by providing a detailed analysis of household food waste and GHG emissions, segmented by age group, in Japan.

This study employed a multi-faceted approach to quantify household food waste (FW) and its associated life cycle GHG emissions (FWGHG) in Japan, segmented by age group. Data sources included the Standard Tables of Food Composition in Japan (STFC), the Food Loss Statistics Survey (FLSS), the Family Income Expenditure Survey (FIES), the Retail Price Survey (RPS), and the National Survey of Family Income and Expenditure (NSFIE). The methodology involved calculating household FW intensity by combining food waste statistics and household- and food-related economic statistics. The structure of total household and age bracket FW were then estimated. Total FWGHG from raw materials to retail and those by age bracket were quantified using life cycle emission inventories (IDEA v3.1.0 and 3EID) and economic and environmental statistics. Finally, projections of the impact of future demographic changes on FW and FWGHG were made based on future trends in the number of households and predicted family size for each age bracket. A crucial step involved converting monetary amounts from FIES into physical amounts consumed per household using RPS data. Where RPS lacked physical unit data, representative commodities were used. Inconsistencies between household statistics and national population statistics were addressed using mathematical programming to optimize family sizes while maintaining consistency with national population data. Life cycle inventory data from IDEA v3.1.0 covered emissions from raw materials to the wholesale stage. Emissions from wholesale to retail were added using 3EID data. Adjustments were made for inconsistencies between the level of analysis (retail vs wholesale) in the data sources. The impact of demographic trends on FW and FWGHG was projected using a model that incorporated changes in the number of households, household sizes, and consumption patterns by age group, assuming that consumption behaviors and production technologies remained constant from the base year (2015).

In 2015, total household FW in Japan was 2.89 Mt/year, with vegetables and fruits accounting for 57% of the total. Per capita FW increased with age, reaching 46.0 kg/cap-year for households in their 70s and older, more than twice that of the 20-and-under group (16.6 kg/cap-year). This was attributed to older households' higher consumption of fresh vegetables and fruits, which are more prone to spoilage. Excessive food preparation was the primary cause of FW for most age groups, except for the youngest, where leftovers were most significant. Total FWGHG was 6.06 Mt-CO2eq/year, with vegetables and ready meals being the largest contributors. Per capita FWGHG was highest for the 60s age group (90.1 kg-CO2eq/cap-year) and lowest for the 20-and-under group (39.2 kg-CO2eq/cap-year). Projections based on demographic trends suggest a slight decrease in total FW and FWGHG by 2040, despite an increase in older households, driven by the overall decline in the population and number of households. The most difficult categories to reduce FW in were fresh fruits, processed vegetables, and salted/dried seafood. However, the most significant reduction potential lied in other soft drinks and instant staple foods.

The study's findings highlight the significant impact of household food waste on GHG emissions in Japan, particularly the disproportionate contribution of older households due to their dietary habits. The results underscore the need for age-specific interventions to achieve the government's food waste reduction targets. While future demographic trends suggest a slight decrease in overall food waste, proactive measures are still necessary to meet the reduction goals. The differential impact of various food categories on GHG emissions (e.g., meat's high emission intensity despite low waste volume) further emphasizes the importance of tailored strategies. The relatively easy reduction potential of FWGHG by reducing meat consumption, or using wasted parts of food more effectively, offers a starting point. However, consideration must be given to potential trade-offs between health-promoting dietary shifts (increasing vegetable and fruit consumption) and increased FW.

This study provides a detailed quantitative analysis of household food waste and its associated GHG emissions in Japan, segmented by age. Key findings reveal a strong correlation between household head age and per capita food waste, driven by increased consumption of perishable foods. While demographic trends suggest some future reduction, targeted interventions are necessary to achieve ambitious reduction targets. Future research should explore the effectiveness of age-specific policies, including educational programs, meal kit development, and improved consumer awareness, as well as further explore the trade-offs between dietary shifts for health and environmental benefits and household food waste.

This study has limitations due to data availability. The analysis excludes food waste from restaurants and takeout, potentially underestimating total food waste. The projection model assumes constant consumption patterns and production technologies, which might not hold true in the future. The FW and FWGHG projections could be refined by using more sophisticated modeling techniques that incorporate factors such as changes in consumer preferences, technological advancements and policy interventions. The reliance on existing datasets also presents some challenges in terms of data consistency and comparability. Furthermore, more precise and complete data on food waste from different parts of the food supply chain would improve the accuracy and comprehensiveness of the study.