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Clarifying Demographic Impacts on Embodied and Materially Retained Carbon towards Climate Change Mitigation

Joint research between Nagasaki University, Tohoku University, Kyushu University and the National Institute for Environmental Studies, Japan has uncovered the demographic impacts on embodied and materially retained carbon, due to our lifestyles and an aging shrinking population in Japan. Indeed, modern lifestyles demand a number of products derived from petroleum-based sources that eventually cause carbon emissions. The quantification of lifestyle and household consumption impacts upon carbon emissions from both the embodied CO2 (EC) and materially retained carbon (MRC) viewpoints is critical to deriving amelioration policies and meeting emission reduction goals.

This study, for the first time, details a methodology to estimate both EC and MRC for Japan, focusing on petrochemicals and woody products leveraging time series input-output-based material flow analysis, and structural decomposition analysis. Findings elucidated hot spots of deleterious consumption by age of householder and the critical factors which underpin them including intensity effects, pattern effects, and demographic shifts over time. Although demographic shifts associated with an aging, shrinking population in Japan decreased EC and MRC, the negative effect reduced in size over time during 1990−2005. Policy implications identify the potential to mitigate approximately 21% of required household emission reductions by 2030 through strategies including recycling initiatives and the recovery of carbon from products covered within current recycling laws and hot spot sectors which are not currently considered such as apparel.

The findings of the research group have strong implications for future climate change mitigation policy in Japan, and in terms of improving understanding of the concepts of EC and MRC as toward recycling, or as a similar concept to the capture and sequestration of carbon (i.e. CCS) if products which contain carbon are not incinerated at their end-of-life. Future goals of this research include the detailing of carbon recovering technologies and an appropriate carbon stock accounting methodology cognizant of waste generation issues.


Schematic figure of embodied CO2 and materially retained carbon derived from household consumption

Schematic figure of embodied CO2 and materially retained carbon derived from household consumption


Yosuke SHIGETOMI, Ph.D. Associate Professor,
Faculty of Environmental Science Nagasaki University