The biogas plant for Pieksämäen Vesi Oy and supplied by Biovoima is almost complete and the plant is fully operational. The biogas plant will use organic sludge from Pieksämäki wastewater treatment plant as raw material and produce biogas from it. The wastewater from the Pieksämäki area will thus be used to produce environmentally friendly energy for beneficial use, making the Pieksämäki central treatment plant self-sufficient in energy.

When it reaches full capacity, Pieksämäen Vesi’s biogas plant will process 6 000 tonnes of wastewater treatment plant sludge and grease trap sludge per year. The economic area covered by the plant has a population of around 17 000. The biogas produced is used to produce 100% renewable electricity and heat for the wastewater treatment plant’s own needs, with the excess energy being fed into the electricity and district heating networks.

We interviewed Tero Kemppi, the project engineer of Biovoima, and Matti Laaksonen, Managing Director of Pieksämäen Vesi, about the biogas plant.

Tero Kemppi, Suomen Biovoima Oy:

How much energy can be produced from the plant?

At full capacity, the biogas plant will produce about 1.8 GWh of energy, roughly split in half between electricity and heat. About a third of this will be used for the biogas plant’s own energy needs, the rest for the Central Purification Plant.

What form has the project taken?

We have been a turnkey supplier for the project. For the client, this is usually an easy and low-risk model, as we have the overall responsibility for meeting the requirements of the tender.

How long has the project been?

The project started in April 2022. The original schedule was delayed by a few months due to the procurement of automation during the war, but surprisingly few delays were encountered.

Could a similar biogas plant be built at any city or municipal sewage treatment plant?

In practice, yes. If we are talking about a smaller sewage treatment plant that does not have enough sludge to meet the feedstock requirements of the smallest viable biogas plant, part of the sewage sludge can be replaced with other organic feedstocks, such as slurry.

What needs to be taken into account and clarified in such a project? What is crucial to the profitability of such a project?

Often, the key to the profitability of small biogas plants is that the energy produced can be used for its own purposes, i.e. it can be used as a substitute for existing purchased energy. Also, gate fees for external feeds increase the profitability of the plant. Of course, the fertiliser benefit of the final product also provides a backbone for profitability, if a suitable buyer for the digestate can be found.

What are the implications of the location of the treatment plant from a sustainability point of view?

If the plant uses its own sludge as feedstock, the location of the biogas plant on the same plot is of course the most sensible solution to avoid logistical costs and emissions. On the other hand, if you are considering a centralised facility that handles the side streams of several different producers, you should consider a location that minimises road transport.


Matti Laaksonen, Managing Director, Pieksämäen Vesi Oy

What were the reasons for Pieksämäki to consider investing in a biogas plant?

The biogas plant project started in early 2020. A biogas consultant contacted us and wanted to present their partners’ possible solutions for building a biogas plant in Pieksämäki. The preliminary studies concluded that it would be better to proceed in stages, starting with a plant using the excess sludge from the treatment plant alone.

What factors were decisive for the decision from the city’s point of view?

The profitability of the project, the calculations were good.

What has been done so far with the sludge from the central treatment plant?

The sludge has been transported to a biogas plant in Kuopio.

How important do you think it is for municipal actors to take bold decisions for a green energy transition?

I see it as very important.

How important do you see the project for your own work?

The biogas plant project is the largest single project of its size ever implemented by Pieksämäen Vesi.

Does the biogas plant require additional labour for the central treatment plant?

So far we haven’t had to, but the future will tell. It now seems that the facility maintenance can be managed internally.

How has the project with Biovoima been going?

The world situation has posed certain challenges to technology supply, but these have been overcome.

How have you estimated the payback period of the investment?

At the start of the project, the payback period was estimated to be around ten years. This will become clearer once the actual yield figures are known.

How will the operation and viability of the biogas plant be ensured in the future?

The facility will be maintained and serviced properly. The amount of biogas produced will be increased with various other fractions from outside the plant, such as grease sludge.


More information:

Eero Tilsala, Suomen Biovoima Oy
+358 40 514 7047

Tero Kemppi, Suomen Biovoima Oy
+358 50 4087100