https://www.nedo.go.jp/news/press/AA5_101917.html

Methane fermentation facilities that use sewage sludge and biomass (livestock waste, food waste, food factory wastewater, etc.) as raw materials generate a large amount of digestate containing 0.1% to 0.3% ammonium ions as wastewater. Currently, the nitrogen concentration is reduced to about 10 ppm mainly through aeration and denitrification treatment using the activated sludge method before discharge, and this treatment consumes a large amount of power

Under a NEDO grant, Kimura Chemical Machinery Co., Kobe University, Novels Co., and FT Biopower Co. have developed Japan’s first energy-saving process for recovering ammonia from methane fermentation digestate. They have used a combination of a forward osmosis membrane in combination with heat pump distillation technology and slaked lime.

A demonstration test was conducted using a bench plant with digestate produced by methane fermentation of sewage and food waste. Under conditions of a digestate (T-N: approximately 1000 ppm) processing rate of 297 t/d, CO2 emissions were reduced by 133 kL (crude oil)/year compared to the conventional method. As an indicator of economic viability, the equipment depreciation period was estimated at 21 years, and the amount of ammonia recovered at that time was estimated at 106 tons (N) per year.

In the future, a collective model will be proposed in which digestate discharged from several locations is primary concentrated and reduced in volume using FO membranes, and then collected in one location for ammonia recovery by distillation. This will promote the social implementation of this process. This will demonstrate a path towards carbon neutrality by 2050 and contribute to further reduction of greenhouse gas emissions in the biogas power generation field and the formation of a locally produced and consumed nitrogen-recycling society.

NEDO began this project in fiscal year 2022, and as part of this project, Kimura Chemical Engineering, Kobe University, Novels, and FT Biopower have been working on developing a highly efficient ammonia recovery technology from low-concentration ammonia-containing wastewater using membrane separation and distillation. Demonstration work began in May 2024 with the Sewerage Department of the Kobe City Construction Bureau, and in June 2025 with the Commerce and Industry Department of Nagaoka City, Niigata Prefecture, resulting in the development of this process, the first of its kind in Japan.