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Visualization tools for your personal carbon footprint to help cut Japan's CO2 emissions

Houses with rooftop solar panels are seen in Yokohama's Totsuka Ward on Feb. 5, 2020. (Mainichi/Kimitaka Takeichi)

TOKYO -- Climate change countermeasures are not just a challenge for governments and companies, but deeply linked to our everyday lifestyles. Tools to help us visualize our own greenhouse gas emissions are now available to encourage people to rethink their behavior.

    60% of greenhouse gas emissions related to everyday activities

    In fact, greenhouse gas emissions associated with our daily lives are surprisingly high. This is because they involve the production, distribution and disposal of any and all things, including foods and everyday items, not just using electricity and gas. Sixty percent of domestic greenhouse gas emissions come from households and regular people going about their lives.

    A "carbon footprint" is one indicator used to visualize emissions, including those we don't see firsthand. It is the total amount of greenhouse gases generated from raw material procurement and production to disposal, converted to a carbon dioxide (CO2) figure.

    Ryu Koide, an environmental engineering researcher at the National Institute for Environmental Studies, and others calculate estimated carbon footprints per capita in Japan's 52 prefectural capitals and government-designated major cities, using information including data from the Internal Affairs and Communications Ministry's Family Income and Expenditure Survey. Koide's team releases the estimated per capita footprints on their website).

    The 52 cities' average annual carbon footprint is 7,300 kilograms of CO2 per person. Broken down by city, the Ibaraki prefectural capital Mito has the highest at 8,430 kg, while Okinawa Prefecture's capital Naha has the lowest at 5,780 kg. To hold down the global average temperature increase to 1.5 degrees Celsius from pre-industrial times, it's said per capita carbon footprints will need to be 2,500-3,200 kg per year by 2030.

    Large regional gaps in greenhouse gas emissions

    A JR Yamanote Line train is seen at Yurakucho Station in Tokyo's Chiyoda Ward on Sept. 16, 2020. An average person's annual carbon footprint for transportation in Tokyo's 23 special wards, where they have a well-established public transportation system, are lower than for leisure. (Mainichi/Yoshinori Matsuda)

    In Mito, 28% of all emissions are linked to "housing," such as electricity, gas and kerosene at 2,390 kg, followed by "transportation" including cars at 25%, or 2,150 kg. Meanwhile in Tokyo's 23 special wards, which have an extensive and well established public transportation system, emissions related to "transportation" account for 12% (850 kg), while "leisure"-related emissions such as dining out total 1,080 kg.

    Cities in cold regions tend to see high housing-linked CO2 emission levels, including heating. Sapporo, capital of the northernmost prefecture Hokkaido, clocks in at 2,760 kg of CO2 from housing, or 36% of all emissions, while transportation is 1,600 kg (21%) and leisure 630 kg, or 8%.

    The research team analyzed 65 options for emission reductions and how much each measure could help reduce emissions in each city. The most promising options, common across the country, included switching from fossil fuel-based electricity to renewable energy sources, which would produce CO2 savings of at least 910 kg on average.

    App to calculate personal carbon footprints

    The National Institute for Environmental Studies and general incorporated association Code for Japan jointly developed and launched an online app where people can check their carbon footprints (in Japanese).

    The app estimates a person's carbon footprint in four areas -- housing, food, transportation and consumption. By answering questions on power usage, what type of transportation the person uses daily, how often they discard expired foods and other topics, the app calculates their carbon footprint and shows countermeasures expected to produce significant emissions reductions.

    The source code for the app is publicly available, so anyone can use it, including for commercial purposes. There are various ways to make use of this function, such as linking it with different apps that let users earn points and applying it to local governments' policy-making efforts.

    Koide said, "By creating a system in which entities like local governments and retail shops encourage residents to change their behavior, I expect that efforts to reduce CO2 emissions will spread."

    (Japanese original by Ai Oba, Science & Environment News Department)

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