Former peatlands remain emission sources after solar farms are built

Former peat production areas can be used for industrial-scale solar power, but they do not automatically become emissions-free, Yle reports. Preliminary findings from a solar farm in Lapua show that the area is still releasing carbon dioxide and methane from residual peat.

More than 300 industrial-scale solar power projects are being developed, proposed or planned in Finland, according to Suomen uusiutuvat. About 40 percent are being built on former peat production areas.

The Heinineva solar farm in Lapua began industrial production at the start of 2026. Its climate emissions have been measured for almost a year as part of the Aurinkosuo research project, which is partly funded by the European Union.

Preliminary findings show that Heinineva is still a net source of emissions. “The residual peat releases slightly more emissions than the vegetation absorbs,” said Kari Laasasenaho, a senior specialist at Seinäjoki University of Applied Sciences.

He said emissions can be reduced by allowing vegetation to develop and by raising and regulating the groundwater level. At Heinineva, water levels are controlled through adjustable subsurface drainage.

As vegetation becomes established, the area’s ability to absorb carbon is expected to improve. Raising the water level is also expected to reduce greenhouse gas emissions over the long term.

The amount of peat remaining after extraction is crucial to the impact of a former peat production area’s subsequent use. A thicker peat layer means more carbon remains stored in material that can decompose and release emissions into the atmosphere, Laasasenaho said.

At the northern end of Heinineva, almost all the peat has been removed, while the southern end has a thicker peat layer. Vegetation is returning naturally in the north, whereas the southern end requires water-level regulation.

Laasasenaho said that, when climate and environmental impacts are considered alone, subsequent uses that reduce emissions should be prioritised. The Environment Ministry directs solar farm construction towards already developed environments, former peat production areas and wasteland.