Nordic energy company Gasum Oy has announced that it is investing EUR 7.5 million in a project aimed at expanding and enhancing its current biogas plant in Riihimäki, Finland. The Riihimäki biogas plant is to undergo a significant conversion focused on the treatment of the digestate that will increase the production of biogas and at the same time enhance the use of recycled nutrients.
The project’s objective is to implement an advanced evaporation system to remove liquid more efficiently from the digestate generated during biogas production.
This addition to the plant process not only boosts operational efficiency but also allows for the recovery of nitrogen in the form of valuable ammonium water.
The plant primarily processes biowaste, sewage sludge, and industrial side streams and the resulting digestate has traditionally been utilized in agriculture, providing essential nutrients to farming as fertilizer. However, the utilization of digestate has faced challenges due to recently revised fertilizer regulations, said Ari Suomilammi, Head of Renewable Gas at Gasum.
Significant reductions in transportation costs and associated emissions
The investment includes an evaporator to remove excess water and a reverse osmosis system to separate and recover valuable nutrients from the digestate.
The resulting product is a solid digestate, resembling soil, suitable for agricultural use and landscaping. Additionally, the thick concentrate can be utilized as fertilizer and the produced ammonium water in industrial processes.
In the context of emission reductions, the investment involves the production of an ammonia solution containing organic nitrogen, strategically replacing nitrogen of fossil origin, specifically urea.
Using this substitute is important in reducing carbon dioxide (CO2) emissions. It helps to decrease about 1,000 tonnes of emissions every year when compared to making regular urea.
The removal of approximately 40,000 tonnes of water annually translates to a significant reduction in transportation costs and associated emissions, sparing the need for a thousand truckloads a year. This not only contributes to environmental sustainability but also enhances the economic viability of the plant, Ari Suomilammi said.
Continued investment in clean biogas production
Increasing the output of existing biogas plants aligns with Gasum’s strategic goal to bring 7 TWh of renewable gas yearly to the market by 2027, resulting in a yearly cumulative CO2 reduction of 1.8 million tonnes for Gasum’s customers.
The Riihimäki biogas plant’s innovative evaporator investment not only addresses current challenges in digestate utilization but also aligns with broader environmental goals.
This investment reflects a commitment to sustainable practices and serves as a model for future biogas facilities looking to enhance their environmental impact. It is not only a question of reducing emissions but also advancing the use of digestate in a manner that is beneficial for the climate and environment, said Ari Suomilammi.
The decision to invest in the Riihimäki expansion was made in January 2024, initiating the planning and procurement phase.
The aim is to have the expansion operational by May 2025. The project has received a grant of 40 percent of the investment sum from the Finnish Ministry of the Environment, emphasizing the government’s commitment to supporting projects advancing the circular economy.
