Development of Scenario and System Analysis and Evaluation Methods

In October 2020, the Japanese government declared its commitment to reduce greenhouse gas emissions to zero by 2050, thus aiming for carbon neutrality by that year. This was followed by the introduction of the “Green Growth Strategy in line with 2050 Carbon Neutrality,” accelerating concrete actions towards realizing a decarbonized society.

“Once we have defined the society we aim for, we need to create scenarios to approach it, measure and evaluate the situation with appropriate indicators, and check the progress,” says Hashimoto, who primarily conducts evaluations and analyses of resource recycling systems from a systems approach, and develops methods and indicators for measurement and evaluation. Recently, he has proposed a new indicator system focusing on the stages of the material lifecycle. He was involved in the 2020 report by the International Resource Panel (IRP), Resource Efficiency and Climate Change: Material Efficiency Strategies for a Low-Carbon Future, delivering impactful publications domestically and internationally.

Calculating the CO₂ Reduction Effect of Ridesharing

“Various efforts are being made towards decarbonization, but no matter how much we reduce CO₂ and lessen environmental impacts, if there are social and economic issues, the efforts will not persist. Further, for example, attempts to reduce waste might cause an increase in other environmental burdens. It’s important not to look at just one aspect but to evaluate multiple aspects,” emphasizes Hashimoto. One of his group’s recent achievements related to decarbonization involves a study evaluating ride-sharing’s environmental, economic, and social aspects.

Ride-sharing (RS) connects drivers with people who want to travel to the same destination via apps, facilitating shared rides. It is gaining attention as a solution that reduces travel costs and CO₂ emissions and meets the needs of the transportation disadvantaged, such as aged people and areas with few public transportation options. Hashimoto and his team used actual data from a long-distance RS service provider to evaluate the environmental, economic, and social aspects.

“From approximately 56,000 records spanning 2015 to 2022, we narrowed our analysis to 19,000 cases where RS was implemented, focusing on long-distance travels across prefectures. These cases were examined and then compared with instances where private cars or public transportation such as buses and trains were utilized instead.”

From an environmental aspect, the assessment of CO₂ emissions showed that using RS could reduce emissions to about one-third compared to individuals driving their private cars. Additionally, it was revealed that CO₂ emissions could be reduced by approximately half compared to scenarios where drivers and other passengers traveled by car and bus, respectively.

Next, the costs associated with transportation were analyzed from an economic perspective, while additional benefits, such as “the opportunity to make connections through RS,” were evaluated from a social perspective, yielding generally positive results. “Overall, it can be considered an effective initiative that contributes to CO₂ reduction,” he concluded.

CO₂ emissions with and without ride-sharing

Evaluating the Environmental Impact of Replacing Plastic Products with Paper Products

Hashimoto has also evaluated the environmental impact of substituting paper for plastic in another study. “Plastic is a convenient material with excellent functions, but recently, ocean pollution and CO₂ emissions from disposal by incineration have become issues, and there is a movement to replace it with other materials like paper. However, when viewed across the entire lifecycle, it remains questionable whether replacing plastics with paper can solve all environmental issues,” he says. Hashimoto and his team have evaluated the environmental impact of substituting several disposable plastic products with paper products using life cycle assessment (LCA). They also conducted a scenario analysis on how replacing plastic products with paper products would impact the environment across Japan.

“We analyzed the environmental impacts at the production and disposal stages of plastic and paper products for items such as plates, lunch boxes, cups, straws, sweets packages, shopping bags (paper bags), and medium-sized beverage containers. We used environmental impact areas from the ‘Life cycle Impact assessment Method based on Endpoint modeling (LIME2)’ for the evaluation.”

The results showed that if 50% of shopping bags and other packaging films, rigid films, and PET bottles were replaced with paper products, it would lead to an estimated CO₂ reduction of about 2.43 million tons. Resource consumption, measured in terms of antimony equivalent, was calculated to be reduced by about 520 tons, a 48% reduction. Meanwhile, land use related to the consumption of wood as paper material, water resources consumption, ecotoxicity, and eutrophication^* all related to paper manufacturing, increased relatively. “This shows that simply substituting plastic with paper does not solve the problem,” says Hashimoto.

Finding a path toward decarbonization amidst these conflicting and complex aspects is not easy. Hashimoto will continue to work on evaluation and indicator development to contribute to its realization.

*Factors inducing the rapid proliferation of plankton and causing water pollution and other issues.

Environmental impact ratio of paper products to plastic products