A group of Japanese companies and researchers has developed a process to recover ammonia cheaply and with lower energy use from wastewater produced in biogas facilities, potentially reducing greenhouse gas emissions and supporting a circular nitrogen economy.
Engineering firm Kimura Chemical Plants Co., together with Kobe University, Novels Co. and FT Bio Power, said on Tuesday that they had successfully developed the process using a combination of forward osmosis membranes, heat-pump distillation and a lime-based ammonia recovery method.
The partners said the technology – the first of its kind in Japan to recover ammonia from methane fermentation digestate – demonstrated significantly improved energy efficiency and economic performance compared with conventional treatment methods.
Methane fermentation facilities that process biomass such as livestock manure, food waste, food factory wastewater and sewage sludge generate large volumes of digestate containing around 0.1 to 0.3 per cent ammonium ions. The liquid waste typically requires energy-intensive treatment before discharge.
When used as fertiliser, the digestate can also pose logistical and environmental challenges, including the need for nearby farmland, rising transport costs, groundwater contamination from excess nitrogen and foul odours during storage.
To address these issues, the four partners have been developing a technology titled “High-efficiency ammonia recovery from low-concentration ammonia-containing wastewater using membrane separation and distillation” under a project funded by Japan’s New Energy and Industrial Technology Development Organization (NEDO) from fiscal 2022 to 2025.
Pilot demonstrations have been conducted with the Kobe city government’s sewerage department since May 2024 and with the city of Nagaoka in Niigata Prefecture since June 2025 to recover ammonium nitrogen from wastewater.
Kimura Chemical Plants has been developing an energy-saving ammonia recovery system that combines heat pump and distillation technologies, while Kobe University has focused on forward osmosis membrane processes that use osmotic pressure to recover useful resources from wastewater with lower energy consumption.
In the project, researchers identified an optimal combination of forward osmosis membranes and heat pump distillation, while confirming the economic benefits of a lime-based ammonia recovery process.
Development steps included designing and building a bench-scale plant based on laboratory tests, conducting long-term trials using real methane fermentation digestate, and incorporating the results into simulation software developed by Kimura Chemical Plants.
Bench-scale tests treating digestate derived from sewage and food waste – with total nitrogen levels of about 1,000 parts per million – processed around 297 tonnes per day, the partners said.
Compared with conventional treatment methods, the process could cut annual carbon dioxide emissions by the equivalent of 133 kilolitres of crude oil. The recovered ammonia is estimated at 106 tonnes of nitrogen per year, with equipment depreciation estimated at about 21 years.
The consortium said it now plans to propose a centralised model in which digestate from multiple sites is first concentrated using forward osmosis membranes and then transported to a single facility for ammonia recovery by distillation.
Such a system could help reduce greenhouse gas emissions in the biogas power sector while enabling the recovered ammonia to be reused, supporting the development of a nitrogen recycling-based society, the developers added.
