The International Energy Agency (IEA) outlined solutions and strategies to achieve net-zero goals in its report "Net Zero by 2050: A Roadmap for the Global Energy Sector". Among these, 55% of emission reductions will come from the deployment of low-carbon technologies and active public involvement, while 8% of emission reductions will directly result from behavioral changes. It will be necessary to guide the public to change their high-carbon lifestyle habits in transportation, housing and diet, and to adopt low-carbon behavioral habits. Only then will there be an opportunity to significantly alter public consumption patterns and industrial structures. 

In brief, achieving the net-zero target by 2050 requires not only thinking from the production side, but also consideration of the impact of consumer behavior changes on carbon reduction. However, it is difficult to systematically quantify the impact of public behavioral changes on carbon reduction by using the prior mainstream approach of surveys or questionnaires. Therefore, the Industrial Technology Research Institute (ITRI) is seeking suitable systematic models for localization in order to facilitate carbon reduction planning for Taiwan going forward. 

A. Household Consumption Accounts for 60% of Carbon Emissions in Japan

Japan is the world's fifth largest carbon emitter. From the production perspective, emissions directly related to consumers account for only 26% of emissions. However, from the consumption perspective, consumption by Japanese households account for 60% of carbon emissions if relevant upstream and downstream industry connections are taken into consideration. A case in point is the inclusion of the energy from the manufacturing to the usage of cars into the carbon emissions attributable to consumers. This makes consumer behavior and choices a key determinant of carbon reduction effectiveness in general. Japan has compiled enough comprehensive base data to create a carbon emission model for consumer behavior. The results show that in 2015, emissions per capita were 7,300 kgCO2e per year. Currently, carbon emissions in almost every city are about twice the target of 3,000 kgCO2e per year by 2030. 

The Industrial Technology Research Institute (ITRI) visited Dr. NANSAI Keisuke at the National Institute for Environmental Studies in Japan. The purpose of the visit was to understand the parameters, definitions, and model construction methods, as well as how to convert from a production perspective to a consumer perspective in a systematic analysis. Unlike past studies mostly centered on the carbon footprint of consumers (based on an app) or calculations of the carbon footprint of a specific product, Dr. Nansai applied a macroeconomic approach and an industrial perspective to quantify all carbon emissions from consumer behavior. 

Japan uses the input-output method to conduct an environmental input-output analysis and calculate carbon intensity. The business-as-usual (BAU) base case is derived from a list of 406 products. This is followed with the estimation of unit carbon reduction based on 25 efficiency options and 40 behavioral change options as reduction measures, as well as greenhouse gas (GHG) inventory intensity, in order to quantify the reduction of carbon footprint as a result of lifestyle changes. For example, carbon intensity can be reduced in Tokyo through a behavioral shift such as giving up driving in favor of taking public transportation; switching to electric vehicles; efficiency measures (e.g., enhancement of vehicle fuel efficiency); demand reduction by conducting online meetings or working from home; and even adopting carpooling or ride-sharing. 

A systematic analysis is performed on carbon reduction differences after consumer behavior shift. The government can formulate strategies based on this model, to further reduce emissions. Going forward, the Japanese research team hopes to calculate more precisely in terms of consumer behavior the carbon emissions from other countries. For example, importing vehicle components from China is equivalent to creating carbon emissions in China. The research will be shared with other countries as a template for evaluating carbon emissions across supply chains.

B. Appropriate Behavioral Shifts Contribute to Carbon Reduction

Taiwan can explore how to gradually establish its own behavioral carbon emission database by learning from Japan. ITRI has established a model integrating the data in Taiwan, such as input-output tables, greenhouse gas emission inventories, and energy balance sheets. The carbon emission calculation is thus converted from a production perspective to a consumption perspective. The carbon emissions from unit production activities in 164 industries are estimated in order to create a behavioral carbon emission model specific to Taiwan. 

ITRI started the carbon emission calculations by going through 14 food categories, including seafood, raw meat, desserts, processed meat products, non-alcoholic beverages, fruits and rice. Carbon intensity and cumulative food consumption were estimated for each category from a consumer perspective. A systematic approach was adopted for the calculation of carbon emissions from diet per capita in Taiwan each year, in the context of behavioral shift, efficiency improvement, and consumption reduction. A strategy for behavioral shift can then be devised to address carbon-intensive diets. 

Consumers are the key to the success of net-zero. It is recommended that Taiwan should enhance the detail of its basic data, conduct calculations to analyze the carbon intensity of domestic consumer behavior, and strengthen cooperation with the National Institute for Environmental Studies in Japan to construct a behavioral carbon emission database suitable for Taiwan.