Carbon balance of forest residue collection and combustion in Southern-Finland

Forest biomass is an important source of bioenergy and its importance is growing even more in the near future. The European Union has given targets for the use of bioenergy and national climate and energy programmes set more detailed, country-specific targets. It is often argued that using biomass in energy production will reduce greenhouse gases along the product's value chain. This argument is based on the fact that biomass is renewable and the carbon dioxide that is emitted during the combustion is absorbed again by the biomass growth. Because time is a relevant factor when studying carbon balances, two time scopes were studied in this paper: 50 years and 100 years. This paper concentrates on collecting spruce harvesting residues after final felling in Southern-Finland. The forest carbon balance is linked to the residue extraction module and further to residue combustion. The emissions from forest residue extraction originate from soil carbon stock change and collecting, transporting and chipping of forest residues. In this paper, the soil carbon stock change caused by residue collection is considered as an emission since soil carbon stock decreases when residues are collected. The results show that if changes in soil carbon balance were excluded and an emission factor for forest residues included only fossil emissions from collection and transporting the residues, a significant amount of emissions would be neglected from the calculations.