Demonstration of Regional Circular Agriculture Ecosystem "Water Circulation x Carbon Circulation" Using Recycled Water Purified from Miyako Island Tropical Fruit Garden "MaiPari" Begins

We have partnered with Green Carbon Co., Ltd. and, under the supervision of Professor Takeki Toyoda of the Department of Biological Systems Science, Graduate School of Agricultural and Life Sciences, Tokyo University of Agriculture and Technology, have begun a demonstration of a regional circular agriculture ecosystem combining "recycled water x biochar" in Miyakojima City, Okinawa Prefecture, starting in April 2026.

This demonstration will verify the effects of reducing chemical fertilizers and forming fertile soil for sustainable agriculture by applying an agricultural material, created by combining recycled water produced from wastewater generated at Miyako Island Tropical Fruit Garden "MaiPari," operated by our group in Miyakojima, using composite fermentation technology, and biochar made from the crushed residue of harvested sugarcane, to sugarcane fields in Miyakojima.

Recycled water is reusable water purified by the action of microorganisms, without the use of any residual chemical agents, by utilizing biological treatment (composite fermentation technology) on wastewater discharged from toilets and kitchens. It can be recycled for flushing toilets in facilities, is rich in organic matter, and enhances microbial activity. In demonstration experiments conducted at Miyako Island Tropical Fruit Garden "MaiPari" from 2023, we confirmed that using recycled water in agriculture enhances microbial activity in the soil and promotes plant growth.

Biochar is a solid material produced by heating biomass such as rice husks and wood at over 350°C in the absence of oxygen. It has characteristics that improve water and fertilizer retention, stabilize soil structure and soil pH, and serve as a habitat for beneficial microorganisms. Therefore, it has been increasingly valued in recent years not only for climate change countermeasures but also as an agricultural material.

In this demonstration, we believe that combining recycled water, which is rich in organic matter and enhances microbial activity, with biochar, which serves as a habitat for microorganisms and retains nutrients, will lead to further yield increases. We will compare and verify the effects of applying recycled water and biochar individually and in combination.

Miyakojima faces the challenge that its limestone geology allows rainwater and chemical fertilizers to easily seep underground, and the presence of many underground dams can cause pollutants to stagnate. At the same time, it is one of the leading agricultural production areas in the prefecture, leading to increased use of chemical fertilizers. Based on the results of this demonstration, we aim to propose "recycled water x biochar" to Miyakojima City and work towards reducing chemical fertilizer use throughout the city.

Through this demonstration, we will create a model for sustainable local production and consumption of water and fertilizer necessary for crop cultivation, and by promoting this model nationwide, including along the Tokyu Line, we will contribute to the realization of a circular society.

Recycled Water Scheme: Roles of Recycled Water and Biochar

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[Appendix]

1. Demonstration Project Overview

2. System

3. Green Carbon Co., Ltd.

Green Carbon is Japan's largest climate tech company, with the vision of "Saving the Earth with the Power of Life," providing end-to-end support for the creation, registration, and sale of natural carbon credits domestically and internationally. In addition, it develops businesses in plant and microbial research and development, ESG/emissions trading consulting, and various environmental-related businesses. Its operations span over 10 countries, primarily in Japan and Southeast Asia, promoting a diverse range of natural projects including paddy fields (mid-season drainage, AWD), biochar, forest conservation, carbon farming, mangrove afforestation, livestock manure treatment, and reduction of livestock-derived methane.

4. Demonstration Image

This demonstration will be conducted under the supervision of Tokyo University of Agriculture and Technology in six test plots at a sugarcane field in the Ueno Nohara area of Miyakojima City. We will compare and verify the effects of applying recycled water and biochar individually and in combination, and also confirm the fertilizer reduction effects. Soil samples will be collected and analyzed regularly to quantitatively evaluate microbial activity, yield, and the degree of soil improvement.

5. About Composite Fermentation Technology

Composite fermentation technology utilizes microbial fermentation to achieve non-chemical wastewater treatment. It also suppresses sludge generation, which occurs in conventional wastewater treatment, and is a sustainable environmental technology in harmony with nature that contributes to zero-emission initiatives.

*Zero Emissions: Achieving zero waste and greenhouse gas emissions from human activities.

6. Past Initiatives and Results

Introduction of Water Circulation System Utilizing Composite Fermentation Technology at Tokyu's Open Innovation Lab "SOIL"

・Period

April 2, 2025 - March 31, 2026

・Location

SOIL (Shibuya Open Innovation Lab)

(Shibuya Konno Daini Building, 3-6-14 Shibuya, Shibuya-ku, Tokyo)

・Verification Items

(1) Verification of material balance in water circulation

In an environment with unspecified users, we aim to establish a system that can flexibly adjust circulation volume according to the environment of the introduced facility by confirming whether the balance of wastewater discharge, recyclable volume, and recycled water usage can be stably maintained in the process of purifying and reusing wastewater with a water circulation system.

(2) Confirmation and quantitative proof of recycled water quality stability

Regular water quality tests of recycled water purified by composite fermentation technology will be conducted to collect more precise data. Evidence proving the stability and safety of water quality will be accumulated.

・Results

(1) Regular water quality tests have been conducted, and the stability and safety of water quality have been confirmed for various test items (e.g., coliform count, pH value).

(2) The water circulation system is operating stably, and the use of tap water has been reduced by approximately 64% within the "SOIL" facility.

・About SOIL (Shibuya Open Innovation Lab)

SOIL is an invitation-only open innovation lab operated by Tokyu, specializing in social implementation. As a soil (SOIL) for open innovation, it provides a place for players such as domestic and international startups, large corporations, investors, media, and government agencies to connect for the development and deployment of new technologies, fostering innovation in Japanese society.

*Past Release https://www.tokyu.co.jp/company/news/pdf/20250407-soil-t.pdf

Demonstration Experiment on Introduction of Water Resource Circulation System Utilizing Composite Fermentation Technology at Miyako Island Tropical Fruit Garden "MaiPari"

・Period

February 27, 2023 - March 31, 2025

・Location

Miyako Island Tropical Fruit Garden "MaiPari" (1210 Shimoji Yonaha, Miyakojima City, Okinawa Prefecture)

・Verification Items

(1) Wastewater discharged from facilities within the premises of Miyako Island Tropical Fruit Garden "MaiPari" will be treated with a composite fermentation facility without using chemical agents such as chlorine, purified to a reusable level, and recycled for flushing toilets in the facilities.

(2) Since recycled water is expected to be a soil conditioner that improves crop growth, recycled water will be sprayed at Miyako Island Tropical Fruit Garden "MaiPari" to measure its effects on improving the growth of safe crops, improving soil and marine environments, and conserving biodiversity.

*Past Release https://www.tokyu.co.jp/company/news/pdf/20230227-1.pdf

・Results

(1) We succeeded in switching all toilet flushing water used within the Miyako Island Tropical Fruit Garden "MaiPari" facility to recycled water, achieving a reduction in tap water usage.

(2) The water circulation system is operating stably, and it has been confirmed to be operating with high processing capacity.

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