Metabolism of materially retained carbon derived by petrochemicals in our society

Climate change and ocean acidification caused by anthropogenic CO2 emission, is perceived as a major threat for the inhabitants on the earth. To manage the level of concentrations of GHGs including CO2, emissions of GHGs are... [ view full abstract ]

Climate change and ocean acidification caused by anthropogenic CO₂ emission, is perceived as a major threat for the inhabitants on the earth. To manage the level of concentrations of GHGs including CO₂, emissions of GHGs are quantitatively discussed by countries, industries and products. However, in addition to the emissions, our economic activities retain carbon as a part of in-use products. For example, more than 10 million tons of plastic resins, mainly consisted of carbon chain, are produced almost entirely from 20% of the imported petroleum in Japan every year. Likewise, considerable amount of carbon is retained in our society. Fate of these carbon depends on the types of products, but much of the retained carbon are eventually released as CO₂ when the products reach their end of life. 

This study reveals how and how much the in-use carbon are retained as products in our society by means of an approach of the input-output based material flow analysis (IO-MFA). IO-MFA with high resolution IO table such as Japanese IO table having over 400 sectors provides carbon contents for products of each sector. Based on the carbon contents of products analyzed by IO-MFA, in-use carbon annually retained in an economy is quantified and its in-use condition is also identified. In this presentation, we mainly focus on retained carbon derived by petrochemical products because of the relatively easier quantification of carbon contents in products. By conducting IO-MFA for petrochemical products based on the Japanese IO table, carbon flow are traced from petrochemicals to various plastic resins and other organic chemical-related products. 

As a result of the analysis, the mass of carbon contained in various products including both short- and long-lifetime products were traced.  Total mass of carbon in domestic final demand in Japan in 2005 was obtained as 8 million t-C, and this mass of carbon was added to the carbon retention that were started in previous years. The mass of carbon corresponds to only 2% of the emitted carbon as CO₂ in the year. Although it is much smaller than the emission, total retained carbon would be much considerable because retained carbon has been added to the society every year since chemical industries developed. Based on this method and preliminary results for the annual addition of carbon retention, we figure out how much carbon has been retained in our society by collecting time series data and the information of average lifetime of products. Then, a model quantifying the metabolism of materially utilized carbon in our society will be developed including consideration of the variety of recycling methods of carbon containing products.