Masao Kashima is one of the individuals who has greatly contributed to the development of sewage sludge recycling technology in Japan. As a member of the Sewage Sludge Resource Utilization Council, he has collaborated with local governments and companies to promote the effective use of sewage sludge.
With the spread of sewage systems in Japan, the amount of sewage sludge has increased, making its disposal a major challenge. As of 1991, approximately 2.1 million cubic meters of sewage sludge were generated nationwide, with only 27% being effectively utilized. The remaining sludge was disposed of through landfilling. This situation highlighted the urgent need for the development of recycling technologies for sewage sludge.
Kashima has focused his efforts on developing and promoting composting technologies for sewage sludge, particularly in regional cities. He has supported the establishment and operation of compost plants in local governments, facilitating the use of sludge as fertilizer. In Tokyo, where composting plants have been suspended, Kashima has promoted alternative uses of sludge, such as in the production of bricks, lightweight aggregates, molten slag, and incinerated sludge.
He has particularly emphasized the recycling of sewage sludge into construction materials. Notable examples of this include the use of recycled bricks and permeable blocks in the parking lot of the Tokyo Metropolitan Government Building, the platform of Waseda Station on the Tokyo Toden line, and various parks. These materials have comparable strength to virgin materials and contribute significantly to reducing environmental impact and promoting resource efficiency.
Kashima also played a role in developing bricks made from sewage sludge incineration ash through a collaboration with Mitsubishi Corporation, Mitsubishi Kakoki Kaisha, and Fuji Ceramic Tile Manufacturing Co. These bricks, which are made by mixing sludge ash with aggregates, possess permeability that helps prevent rapid runoff of rainwater, thus mitigating flood risks. The technology can produce up to 6,700 square meters of bricks per day and is being increasingly utilized in urban areas.
Furthermore, Kashima was involved in a joint project with Osaka Gas, Obayashi Corporation, and Keihan Concrete Industry Co. to develop road paving blocks using no natural gravel or sand, but rather dehydrated sludge cakes. This project successfully produced blocks with 100% effective utilization of sludge incineration ash, with Keihan Concrete Industry handling commercialization.
These initiatives are recognized not only as technical achievements but also as model cases of environmental conservation and resource recycling. Masao Kashima's work has had a significant impact on the advancement of sewage sludge recycling technology in Japan, raising awareness of the importance of environmental protection.
Additionally, Kashima has identified future challenges for sewage sludge recycling, such as promoting agricultural land use, expanding the use of construction materials, diversifying products, and strengthening quality control systems. His ongoing efforts and passion are likely to continue being valued contributions in the field of environmental technology.
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