Energy return on investment and environmental performance of post-peatland restoration pathways

Abstract

The use of peat in energy production is shrinking in Finland. As the country moves towards phasing out peat for energy production, large areas of post-harvest peatland are being left. This transition creates challenges in the local economy, energy supply, environmental and ecological balance. Restoration of drained and abandoned peatland through cultivation of energy crops was found to be effective.

This master's thesis analyzes the two restoration pathways through willow and reed canary grass in terms of Energy return on Investment (EROI) and their environmental performance, specifically global warming potential (GWP) and acidification potential (AP). The results show that the willow–biochar pathway performs better when biochar is used for local heating than as a soil amendment. The EROI is 6.13 when biochar is used for heating and 3.75 when it is applied to soil. The reed canary grass pathway, where the biomass is used as animal bedding and later processed into biogas, also shows positive performance with an EROI of 4.01.

In terms of Global Warming Potential (GWP), both restoration pathways are net carbon negative. The willow–biochar pathway removes 4438.1 kg CO₂-eq per hectare per year when biochar is used as a soil amendment. When biochar is used for local heating, the system removes 3711.9 kg CO₂-eq per hectare per year. The reed canary grass pathway shows more potential for carbon removal, with a net reduction of 11697.3 kg CO₂-eq per hectare per year.

Regarding Acidification Potential (AP), the reed canary grass pathway performs better, showing a net negative impact of -4.3 kg SO₂-eq per hectare per year. In comparison, the willow–biochar pathway results in a small positive acidification impact. The AP is 1.08 kg SO₂-eq per hectare per year when biochar is used for local heating and 0.9 kg SO₂-eq per hectare per year when it is applied as a soil amendment.