The Need for Toyosu and Brownfield Measures - November 2007 to the 2020s

The Need for Toyosu and Brownfield Measures - November 2007 to the 2020s

### Historical Background
There are approximately 28,000 hectares of brownfields in Japan, including the former Tokyo Gas plant site in Toyosu, Koto-ku, Tokyo, with an estimated asset size of approximately 108 billion yen. Of these, in Toyosu, concentrations far exceeding environmental standards (benzene: 0.01 mg/L), specifically 10 mg/L or more, have been detected, and the cleanup cost is estimated at approximately 67 billion yen.

In particular, when contamination was discovered prior to land sales, the cleanup costs exceeded 20-40% of the land price, causing transactions to stall in many cases. The Ministry of the Environment is promoting the development of the Soil Contamination Countermeasures Law and supporting land reuse by reducing the risk of contamination through such measures as a simplified risk assessment service provided by Kokusai Kogyo. On the other hand, local cities lagged behind in implementing countermeasures, and the challenges were more pronounced in economically depressed areas.

### Developments in the 2010s
In the 2010s, low-cost purification technologies for heavy metal-contaminated soil became widespread, and the on-site technologies developed by EBARA and DOWA Eco-System attracted attention. EBARA's technology made it possible to treat soil containing lead and arsenic at a cost 50% lower than conventional methods, saving approximately 1,500 yen per square meter.

In addition, as of 2019, about 12 million cubic meters of contaminated soil had been treated in special decontamination areas due to radioactive contamination caused by the Fukushima Daiichi Nuclear Power Plant accident. The government has invested approximately 2 trillion yen to facilitate the return of residents. In the real estate industry, risk assessments by third-party organizations have been standardized, and transparency in land transactions has improved.

In urban redevelopment, the construction of eco-cities and zero-emission towns has attracted attention since the late 2010s, and the reuse of contaminated land has expanded. For example, in Osaka City, the "Yumeshima Redevelopment Project" is underway, utilizing the site of a former factory, with a total investment estimated at approximately 200 billion yen.

### Current Status in the 2020s
In the 2020s, the number of surveys of contaminated land is on the rise: in FY2022, 1,576 soil contamination surveys were conducted, of which 982 confirmed contamination exceeding environmental standards. In Toyosu, soil contamination by toxic substances such as benzene and cyanide continues to be an issue, and the total cost of cleanup is expected to increase further.

EnBio Holdings is promoting a project to clean up contaminated land at a cost of approximately 20 million yen per case. In some cases, the cost of remediation measures in local municipalities has reached 30-50% of the land price, making redevelopment difficult. On the other hand, a new cleanup technology, a toxic substance decomposition method using nanoparticles, is in the research stage and is expected to reduce costs.

**Summary**.
The brownfields issue, including Toyosu, is an important challenge to strike a balance between land use and environmental preservation. 2010s have seen technological innovation and institutional development, and the 2020s will require further development of remediation technologies and financial support. Sustainable urban development should continue to be promoted through the reuse of contaminated land.