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Central Japan city aims to collect plastic waste by setting up nets in rivers, canals

Netting set up to collect plastic waste for a long-term project is seen in the central Japan city of Toyama on May 19, 2021. (Mainichi/Kenta Sunaoshi)

TOYAMA -- This central Japan city has commenced a long-term experiment on collecting plastic waste with nets placed in rivers and irrigation canals, in a bid to prevent household plastics from flowing into the ocean.

    The project, started by the Toyama Municipal Government this spring, will continue for six months and aims to enhance the efficiency of collecting trash through accumulated experience, as well as establish a method for easily sustaining and managing its system.

    The city has repeatedly modified its original "Toyama model," which puts to practical use a mechanism of gathering driftwood and garbage floating on the water's surface through netting set up in dams, reservoirs and other places. It is a simple system that gathers and collects plastic waste which flowed into rivers and irrigation canals after being littered outside.

    Following short trials conducted in the winter of 2019 and the summer of 2020, the current project has brought the model a step closer to its practical implementation. The city wishes to spread the concept to other municipalities in the future.

    In December 2019, the municipal government chose five locations at rivers and irrigation canals within the city as model sites, and had nets set up in these locations for the first time over a course of five days. In August 2020, sites were narrowed down to three spots which were expected to yield favorable results, and the netting was in place for about two months while officials examined the amount of trash which was collected.

    As a result, 373 kilograms of waste was collected during two months from Game River, which flows in a central area of the city. While a majority of the trash collected were plants and twigs, plastic waste including plastic bottles, bento lunch box containers and plastic bags weighed up to 39.4 kilograms, accounting for more than 10% of the total.

    Additionally, 7.3 kilograms of plastic waste were collected in the Hirota irrigation canal which is used in farming and located in a suburban area, while 2.6 kilograms of plastics had gathered in the Senbyo irrigation canal. A total of 49.3 kilograms of plastic waste was collected from the three locations.

    Not only is the Toyama model designed to collect as much plastic waste as possible, but it is also environmentally friendly. Taking into account that plastic tends to float in water, floats were attached to the nets so that they could pick up trash near the water's surface.

    Each mesh square is 5 centimeters on either side, and it is made so that the nets would neither hinder the flow of the river nor negatively impact fish and other creatures living in the river. Two nets were set up as one pair, and were made into a two-fold structure where trash which passed through the first net could still be caught by the second.

    Although previous tests had been held for short periods during the summer or winter, this time around, the city will examine the trash-collecting system's effects across the long period of around six months between May and November, which includes both a period where rivers and canals are filled with much water due to the melting of snow and seasonal rain, as well as a period during the summer in which the amount of water decreases.

    As rivers across Toyama Prefecture flow into Toyama Bay, the city of Toyama regards the issue of oceanic waste as a challenge which should be addressed by all municipalities within the prefecture. The municipal government plans to inform neighboring municipalities of its investigation results after the trial this year is finished, and share knowhow on ways to collect plastic waste if there are any requests.

    Yusuke Nose, deputy chief of the Toyama Municipal Government's environmental policy division, said, "By collecting waste including plastic bottles in a form visible to us, I'd like residents to witness the reality of massive waste flowing in rivers and other places." He hopes that this will then lead to the reduction of plastic waste in each household.

    (Japanese original by Kenta Sunaoshi, Toyama Bureau)

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