DSII industry visit: Turning waste into energy at Tarastenjärvi

DSII participants recently had the opportunity to visit Tammervoima’s waste power plant Tarastenjärvi, a key piece of energy infrastructure in Tampere region. The plant offers an example of how society’s unavoidable waste can be transformed into useful thermal and electrical energy.

Arriving at the plant, some of us, myself included, expected that there would be an awful predominant smell. At the previous waste-to-energy plant of similar size I visited in Kvevlax (Westenergy), the smell was horrid, so I was expecting the same this time. I learned that most of the odour must have come from biogas production at the same site and not the waste-to-energy plant itself. Also, recycling has improved a lot during the past decades so that must play a role too. We were already learning things even before entering the plant.

The visit began with a presentation on the plant and a brief peek to its automation system provided by Ville Leskinen. We learned that in developed countries, municipal waste is no longer sent to landfills. While recycling has improved significantly over the past decades, a portion of mixed waste remains unavoidable. The plant collects mixed municipal waste primarily from the Tampere region and combusts it using a grate type incinerator (Finnish: "arinakattila"). The combustion process produces both electricity and heat, along with flue gases such as carbon dioxide. The generated electricity is sold and fed to the electrical power network, and the thermal energy is supplied to Tampere’s district heating network.

The plant is jointly owned by Tampereen Energia Oy and Pirkanmaan Jätehuolto Oy, both of which are owned by municipalities. It is operated in close coordination with the other local energy facilities, such as Naistenlahti power plant. While considering electricity market prices (among other factors), the operation is primarily driven by the needs of the district heat network. Due to the low fuel costs, it operates as a baseload facility. Planned maintenance typically accounts for only two weeks annually, with unplanned downtime limited to roughly one day per year – though both are expected to increase as the plant ages.

Waste combustion operates continuously within strict environmental regulations. Residue materials, like ash and different metals, are sorted. Emissions in the flue gases are monitored constantly. If any regulatory limits are exceeded, the plant is shut down as soon as possible. While, among other things, the process emits carbon dioxide, plans are underway to integrate the plant with an efuel production facility that would capture and utilize the carbon dioxide. Ultimately, burning these e-fuels in lorries and similar vehicles would still release CO₂ into the atmosphere. However, compared to today’s fossil fuels, this would be an improvement from the perspective of the carbon cycle.

From a technical perspective, the boiler operates at temperatures of around 1000 °C or more. At these temperatures some metals, such as aluminum, melt, while others, like steel and nickel, do not. During the tour, we even saw examples of items that had survived the combustion process almost unaffected, such as cast iron objects, for example.

The visit concluded with a guided tour to the boiler and control rooms. In the control room we observed the crane lifting waste into the boiler, and the staff working and observing different alarms based on metered values from the system. Finally we got to see the flames in the boiler, which was the highlight of the visit for me!

Overall, the visit offered a valuable peek into the operations of a waste-to-heat power plant. It served as a reminder that improving sustainability is not just developing new technologies, but also continuously improving the systems that already exist.

And finally, please remember to recycle. It matters what you put into the mixed waste bin. If you put material of low heat value – e.g. wet biodegradable things – it will have a toll on the combustion process. If you put in different metals, e.g. aluminum, that also has an impact on the maintenance of the plant.

Remember, a large improvement in sustainability may be achieved from a single large action but also from multiple smaller ones on a large scale.