Solar power on cutaway peatlands - combining renewable energy generation and soil carbon sequestration

Solar photovoltaic (PV) power is expected to expand significantly in Finland. This growth requires large land areas, up to 70,000 ha, which often comes at the expense of forests or agricultural land, risking deforestation and soil carbon losses that undermine Finland’s land-use climate targets. A promising alternative for large-scale solar deployment in Finland could be the former cutaway peatlands with an area of ca. 90,000 ha. These sites continue to emit CO₂ and other greenhouse gases due to the decomposition of residual peat layers. Solar energy is increasingly favored by landowners as an after-use option, alongside forestry and agriculture. Combining PV deployment with water table restoration could, on the other hand, reduce peat decomposition and GHG emissions and improve biodiversity.

However, key scientific and techno-economic uncertainties remain and require targeted research. The SolarCarbon project will address these knowledge gaps by 1) measuring the greenhouse gas and energy fluxes between the ecosystem and the atmosphere above cutaway peatlands with PV installments; 2) estimating the climate impact reduction potential of the possible water level management; 3) estimating how solar arrays on cutaway peatlands impact their local climate through changes in surface biophysical properties and solar energy partitioning; 4) generalizing the measurements to other locations and making GHG scenarios following future climate and land use projections; 5) evaluating the techno-economic potential of PV siting options and their impacts in the Northern European energy system in a range of alternative future scenarios; and 6) quantifying the overall benefits of cutaway peatland PV for the green transition and decarbonization of Nordic countries.

We produce new knowledge on the PV installations’ impact on cutaway peatlands’ micrometeorology and GHG fluxes, the techno-economic potential of PV and its dependence on the energy system flexibility, and the contribution of PV on cutaway peatlands to decarbonisation’, considering both the energy and soil carbon sequestration impacts. The results can be directly utilized in the scientific community, but also local and national decision-making and in energy companies planning.

SolarCarbon investigates combining solar power and soil carbon sequestration on cutaway peatlands. Solar power capacity is increasing rapidly and competes for land -area with forestry and agriculture. Countries like Finland have large areas of cutaway peatlands where peat production has ceased yet significant greenhouse gas emissions are still produced owing to the leftover peat under drainage. Combining solar power and rewetting on such sites promises multiple benefits, such as renewable energy, carbon storage and increased biodiversity.

The project aims to address the following research gaps: How do solar power and rewetting impact the greenhouse gas emissions and the carbon storage in leftover peat? What is the solar power potential of cutaway peatlands considering the site locations and the overall role of solar power in future energy systems? If cutaway peatlands were to be fully exploited in this manner, how much would it benefit society's decarbonization efforts?