Comparison of city-level carbon footprint evaluation by applying single- and multi-regional input-output tables.

City-level carbon footprint has been recognized as a useful measure of anthropogenic impact on climate change associated with citizens' activities within the administrative boundary. Although the promotion of consumer responsibility suggests rethinking urban indirect emissions, the detailed methodology is far from satisfactory for realistic applications. Due to the lack of multi-regional input-output tables for most cities, there is a wide application of single regional input-output tables. However, there still lacks further discussion on if there will be an obvious evaluation bias by applying city-level single-regional tables rather than multi-regional ones. To visualize the table coverage on its application consequence, both single- and multi-regional input-output tables were employed to compare disparities in the carbon footprint accounting in the case of Tokyo, Japan. Our analysis shows that the gap of emissions driven by Tokyo's final demand between single- and multi-regional input-output tables was considerably large. Furthermore, the results of multi-regional table were found to be 8.11 MtC higher for coal-generated emissions, 7.83 MtC for crude oil-generated emissions and 2.90 MtC for natural gas-generated emissions than those of the single-regional table. The largest deviation in emissions accounting was observed in the power, gas and heating supply sector, the construction sector and the private service sector. The gap between these two input-output tables was notable for all three types of fossil fuels (coal, crude oil and natural gas). These indicated that coal-generated emissions have been largely ignored by single-regional input-output table. The study highlighted the difference of carbon footprint accounting between these two types of input-output tables. Our findings are intended to assist policymakers and scholars in pinpointing and reallocating sectors that are likely to yield severely biased evaluation of emissions embodied in trade when a multi-regional table is not available.

Mixed diets can meet nutrient requirements with lower carbon footprints.

Achieving sustainable dietary change is essential for safeguarding human and environmental health. However, dietary recommendations based on broad food groups may not accurately reflect real-world realities because individuals select and consume dishes with multiple food items influenced by diverse context-specific factors. Therefore, here we explored the sustainability trade-offs of dietary choices at the dish level through an optimization modeling approach tested in Japan. We estimated the nutritional quality, price, and carbon footprint of major Japanese dishes and examined 16 dietary scenarios to identify options that meet the nutritional requirements and minimize carbon footprint. Overall, mixed diets contain more combinations of dishes that meet nutritional requirements with lower carbon footprints compared to more restrictive dietary scenarios. We argue that the approach developed here enables a better understanding of dietary trade-offs, complements existing methods, and helps identify sustainable diets by offering nuanced information at the national and sub-national levels.

Carbon footprint and embodied nutrition evaluation of 388 recipes.

Food consumption, which delivers fundamental energy and essential nutrients to human beings, is crucial for achieving a series of sustainable goals. Alongside rising population growth and living standards, there has been a significant increase in food cultivation demands, supply chain complexities, and waste management. Therefore, to protect human health and the environment, promoting sustainable food systems and the uptake of sustainable dietary habits are vital. Yet, information on the environmental and health impact of dietary choices remains inconsistent across multiple evaluation methods, which fail to deliver essential ideas to consumers. In this study, we formulate an integrated approach using Environmentally Extended Input-Output analysis, covering the food supply chain from production to the distribution phase, complemented with a hybrid Life Cycle Assessment for cooking and disposal processes, to quantify the carbon footprint of specific recipes. Our dataset also includes the distinct nutritional values of each recipe. This dataset not only informs the food industry and recipe platforms, enabling more sustainable choices, but also helps individuals balance nutritional value with environmental impact, leading to more informed and sustainable dietary decisions.

Extension and update of multiscale monthly household carbon footprint in Japan from 2011 to 2022.

Household consumption significantly contributes to greenhouse gas emissions as it is the largest component of final demand in the national accounting system. Nevertheless, there is an apparent lack of comprehensive and consistent datasets detailing emissions from household consumption. Here, we expand and update Japan's multiscale monthly household carbon footprint from January 2011 to September 2022, combining data from government statistics and surveys. We constructed a dataset comprising 37,692 direct and 4,852,845 indirect emission records, covering households at the national, regional, and prefectural city levels. The dataset provides critical spatiotemporal information that allows for revealing carbon emission patterns, pinpointing primary sources of emissions, and discerning regional variances. Moreover, the inclusion of micro-scale carbon footprint data enables the identification of specific consumption habits, thereby regulating individual consumption behavior to achieve a low-carbon society.

Japanese urban household carbon footprints during early-stage COVID-19 pandemic were consistent with those over the past decade.

As urbanization accelerates worldwide, substantial energy and services are required to meet the demand from cities, making cities major contributors to adverse environmental consequences. To bridge the knowledge gap in the absence of fine-grained city-level climate protection measures due to data availability and accuracy, this study provides a detailed carbon emission inventory for analyzing the monthly fluctuations based on citizens' daily consumption behaviors. Here, carbon emissions embodied in approximately 500 household consumption items were calculated in 47 prefectural-level cities in Japan from 2011 to June 2021. We analyzed the results considering the regional, seasonal, demand, and emission way-specific aspects, and compared the emission before and during the COVID-19 pandemic. Notably, the carbon footprints during the pandemic were consistent with the previous level despite downtrends in specific categories. This study provides an example of utilizing city-level emission data to improve household green consumption behavior as references for enriching city-level decarbonization paths.

Monthly direct and indirect greenhouse gases emissions from household consumption in the major Japanese cities.

Urban household consumption contributes substantially to global greenhouse gases (GHGs) emissions. Urban household emissions encompass both direct and indirect emissions, with the former associated with the direct use of fossil fuels and the latter with the emissions embodied in the consumed goods and services. However, there is a lack of consistent and comprehensive datasets outlining in great detail emissions from urban household consumption. To bridge this data gap, we construct an emission inventory of urban household emissions for 52 major cities in Japan that covers around 500 emission categories. The dataset spans from January 2011 to December 2015 and contains 12,384 data records for direct emissions and 1,543,128 records for indirect emissions. Direct emission intensity is provided in g-CO2/JPY to facilitate both future studies of household emission in Japan, as well as act as a reference for the development of detailed household emission inventories in other countries.

Japan prefectural emission accounts and socioeconomic data 2007 to 2015.

In the wake of the Fukushima nuclear disaster, Japan largely moved away from nuclear power generation and turned back towards an energy sector dominated by fossil fuels. As a result, the pace towards reaching emission reduction targets has largely slowed down. This situation indicates that higher emissions will continue to be generated if there is no appropriate and efficient measurement implemented to bridge the energy demand gap. To contribute adequate mitigation policies, a detailed inventory of both CO2 emissions and socioeconomic factors, both at the national and regional level, should be issued. Thereby, this work contributes to a time-series emission with a record of 47 prefectures in Japan as well as their associated socioeconomic features. The compiled emission inventory is based on three major fossil fuels and 26 sectors with careful emission allocations for regional electricity generation. This dataset is uniformly formatted and can be expected to provide vital information to set regional reduction allowances and sectoral reduction priorities.