PS 27-128 - Comparison on greenhouse gas emission reduction by photovoltaic and carbon sequestration by forests: A case study of solar power generation in Korea

Abstract: Renewable energy projects are rapidly increasing worldwide as countries aim to meet the goals of the IPCC and Nationally Determined Contributions (NDC) to reduce greenhouse gas (GHG) emissions. Similarly, the construction of renewable energy has been on the rise in South Korea since 2017. With approximately 63% of land cover consisting of forests, forest destruction resulting from the expansion of renewable energy is an unavoidable issue in Korea. Solar-power in forestland accounts for the largest proportion, representing over 60% of the total onshore photovoltaic. The objective of this research is to compare the greenhouse gas (GHG) emission reduction and forest carbon sequestration of solar power generation projects implemented on forestland. A total of 100 sites that replaced forests were selected. The annual GHG emission reduction of photovoltaics was estimated using the formula presented in the "Guidelines for Operation of Greenhouse Gas Energy Target Management in the Public Sector" by the Ministry of Environment in 2016. For estimation of carbon sequestration and storage, it was assumed that the forest was not replaced. Carbon sequestration was calculated using various carbon emission (absorption) coefficients, such as basic wood density, biomass expansion factor, root-to-shoot ratio, and carbon conversion factor. Carbon storage of replaced forests was estimated by summation of the carbon stored in forest biomass, litter layer, and forest soil. The average annual GHG emission reduction by photovoltaics exceeded the annual carbon sequestration of forests by over 40 times when comparing results across all sites. When accounting for the carbon storage capacity of the replaced forests, the difference between photovoltaics and forests decreased. Although the general lifespan of photovoltaic panels is shorter than that of trees, it was estimated that more than 500 years are required for carbon sequestration in forests to outperform GHG emission reductions due to photovoltaics. These findings might suggest that photovoltaics have the potential to replace forests in reducing GHG emissions. However, it should be noted that this study did not consider the potential environmental and ecological impacts of such a replacement. This study is expected to provide foundational data for future research on sustainable development.