From sewage sludge to agriculture: governmental initiatives, technologies, and sustainable practices in Japan

Sewage sludge (SS), an underutilized but valuable resource for agriculture, contains essential nutrients, such as phosphorus. In Japan, where dependence on imported fertilizers is high and global price fluctuations persist, using SS as fertilizer presents a sustainable alternative aligned with circular economy goals. This review analyzes Japan’s current efforts to repurpose SS, focusing on technological developments and key policy initiatives that promote safe and effective application. Selective phosphorus recovery technologies mitigate resource depletion, while holistic approaches, such as composting and carbonization, maximize sludge utilization for agricultural applications. Government-led initiatives, including public awareness campaigns, quality assurance standards and research support, have facilitated the adoption of sludge-based fertilizers. To contextualize Japan’s position, international trends, particularly in the EU, are also examined. These comparisons reveal both common strategies and areas for policy and technological advancement, especially regarding regulation of emerging contaminants. By integrating national case studies with global perspectives, the study offers insights into the economic, environmental, and social benefits of SS reuse, contributing to Japan’s goals of resource self-sufficiency and carbon neutrality, while also informing broader sustainable agriculture transitions worldwide.