”Return to the soil” circular sensors
SANKEN, Osaka University
Story
Once, Japan was among the world’s leading circular societies, and the Satoyama landscape of Miyoshi town in Saitama Prefecture, where TOILETOWA now stands, has been cherished and preserved by its people for over 300 years. All planted trees were deciduous, and compost made from fallen leaves nourished both the forests and crops, perpetuating a cycle in which leaves would fall and return to the soil as compost once more. This established a model of circular agriculture, where living in harmony with nature was a natural way of life. TOILETOWA was born from a strong desire to revive this cycle, dating back to the Edo period, and to convey the importance of the microorganisms essential to soil creation. The initiative aims to share this vision first with employees, then with visitors, and eventually with children, carrying forward the wisdom of this cycle into the future.
Material Circulation and Regeneration:
The toilet building is constructed primarily with materials that are either 'returnable to the earth' or recycled, without the use of concrete. The main material, NS-10, is a type of reclaimed soil jointly developed by Ishizaka Sangyo, the building’s owner, and IS Engineering. It is refined at Ishizaka’s facility from a mixture of gypsum board and soil, sourced from the demolition materials of residential houses brought in by housing manufacturers. Although NS-10 has traditionally only been used as a base material for pavement, this marks its first application as a construction material. Additionally, recycled materials such as wood, wood chips, and old roof tiles are used throughout the building.
Circulation of Craft Techniques:
The woodwork was crafted by young carpenters using traditional hand-carving methods. Plastering techniques such as rammed earth, plastered walls, tataki-doma (earthen floors), and polished mortar have also been incorporated, promoting not only material circulation but also the preservation and revitalization of traditional woodworking and earthen techniques.
Complete Circulation of Toilet Wastewater and Revitalization of Gardens and Trees:
The treatment and regeneration of toilet wastewater utilize a biotechnology known as complex fermentation (ENBC). Powered by countless microbial cultures, the water is purified, eliminating harmful bacteria, pathogens, and E. coli, resulting in an odorless and crystal-clear liquid, clean enough to drink. This purified water is then directed to nourish the surrounding garden and trees around the tank building, contributing to new cycles of life.
Regeneration of the Earth:
With the construction of the toilet building, efforts were also made to restore the surrounding forest and soil, which had weakened over time. This "Regeneration of the Earth" project centered around the toilet building, revitalizing the forest as part of the landscaping work. Locally sourced, plant-based materials such as branches, fallen leaves, bamboo charcoal, rice husk charcoal, and old roof tiles were buried vertically and horizontally in the soil. This technique created natural water and air pathways underground, enhancing soil aggregation and stimulating the activities of fungal mycelia, root systems, microorganisms, and soil-dwelling organisms, ultimately nurturing the soil's inherent vitality.
Previously compacted and poorly draining soil no longer formed puddles, resulting in a fresher, more vibrant flow that encourages tree regeneration. The project fostered a tangible cycle of water and air in the forest, connecting soil, trees, architecture, and earth. Through this regeneration effort, an invisible water cycle was achieved both within the soil and in the air, working in harmony with the complex fermentation water circulation from the toilet building to restore the forest ecosystem.
Education of People:
Currently, Ishizaka Sangyo provides an educational program to its employees, not only explaining the mechanisms and management of TOILETOWA but also conveying the values and philosophy of circulation and regeneration. The aim is for employees to pass this knowledge on to the general visitors who come here, and further, to ensure it reaches the children who will shape the future.