Technical Alternatives and Energy in LCA

This licentiate thesis is based on two papers, a comparative LCA case study paper and a paper on energy issues in LCA. A case study was done in order to investigate which of two compared technologies for chemical recovery in the pulp industry (recovery boiler, RB, or black liquor gasification, BLG) is environmentally favourable. The chemical recovery processes by themselves are not the dominant contributors to the life cycle environmental effects. Instead, the production chains of the chemical and energy inputs to the processes dominate. An analysis based on current LCIA environmental performance indices gives an unequivocal answer to the main question, although the strength of the answer varies between different impact assessment methods. However, the BLG process is better for the environment. If the BLG process would switch from oil to biofuel in its causticising plant, it would become clearly superior. The energy paper analyses and elucidates some problems with the way energy is treated in LCA methodology. For most products and production processes, several quite different forms of energy are involved in different stages in the life cycle. There is no indisputable general method for comparing and aggregating these energy forms when performing an LCI, nor is there any general method for the valuation needed for the weighting in an LCIA. Some possibilities for and limitations on resolving these problems are discussed