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The Finspång model

The Finspång model was developed from the Axsäter wastewater treatment plant in Finspång with the support of the Swedish Energy Agency. The model is a total solution for the digestion of sewage sludge; it comprises all the necessary peripheral technical systems and safety classification for an MR biogas plant.

By ordering an MR of the Finspång model, the customer receives a tried-and-tested solution for the long-term and which includes both hard and soft innovations.

Plug flow technology

In the Finspång model, sewage sludge is digested in an MR biogas reactor based on plug flow technology. The technology provides a highly efficient, low energy digestion process.

Thickening and preheating raw sludge


Sewage sludge is thickened to a DS level of around 9-10% and preheated to the correct digestion temperature before entering the reactor. This allows reactor volume to be utilized to the full as the amount of water occupying space is drastically reduced in comparison with conventional digestion methods. By preheating the substrate, plug flow is not disrupted as no circulation flow is necessary through the reactor.

Thermophilic digestion

The Finspång model uses digestion at thermophilic temperatures to reduce substrate will time and thus optimize the capacity of the reactor. The substrate is preheated to 55°C whereafter the temperature is kept constant using reactor jacket heating.


Reactor dwell time is adapted such that, in combination with the thermophilic temperature range, it generates hygienized digestion residues. Plug flow technology ensures that fully digested, hygienized substrate is never mixed with undigested material.

Hygienization inside the biogas reactor saves both space and money compared to other methods.


In the Finspång model, extracted biogas is used locally in a microturbine. It generates enough electricity to meet one third of the treatment plant’s annual needs. Exhaust gas energy from the microturbine is used to heat premises and processes. When additional heating is required, an existing gas/oil fired boiler is used.


The installation is designed to be intrinsically safe, which means no fire compartmentation required. Time mentioning is based on controlled process ventilation and all electrical equipment meets IP67 standards. Installation safety meets international safety requirements.

Process ventilation means no gas emissions pose risks at the installation. The installation design is based on safety analyses conducted together with specialists with international experience in gas processing. Project planning is carried out with a systematic review of all risks from the planning stage to completion and commissioning.


We can provide financial leasing for biogas projects. This allows the customer to avoid charging large investments to the balance sheet and instead pay for the installation through leasing charges proportional to the current residual value. A well-maintained, well-cared-for installation enjoys a significantly higher residual value leading to very favourable financing over time. Expenditures and investments arising during the construction and lease time can simply be included in the current agreement.

No expenditure for the client/purchaser is necessary until the installation enters operation.