Life cycle assessment of light sources – Case studies and review of the analyses

Lighting is a major global consumer of electricity and undergoing drastic changes due to legislative and voluntary measures. Widely-used conventional light sources, such as incandescent lamps and high pressure mercury lamps, are banned from the European Union market. The number of light sources on the market is expanding especially regarding the LED lamps and luminaires. These major changes in the lighting sector create a need for evaluating the environmental performance of light sources, especially as the changes are justified by the environmental aspects, such as energy consumption. The life cycle assessment method is standardized on a general level, but no established rules exist for conducting a life cycle assessment of light sources in detail. In most cases, it is impossible to directly compare the results of different assessments. Because of the major changes in the lighting market, it is useful to assess the environmental impacts of various light sources in similar methods. The work addresses this problem by presenting two models, a simple and an extensive one, for conducting the life cycle assessment of light sources rapidly and in a transparent, comparative way. The models are developed on the basis of four case studies presented in the work and a review to the life cycle assessment found in the literature. Both models are simplified, and they recommend the key parameters of the life cycle assessment: functional unit, stages of the life cycle, environmental impacts, and energy source in use stage. Four case studies were conducted in the work: two life cycle assessments of a fluorescent lamp luminaire and an LED downlight luminaire, one life cycle cost analysis of street lighting luminaires, and one analysis combining both life cycle assessment and life cycle cost analysis of non-directional lamps. The case studies and the review of the previous life cycle assessments concluded similar findings despite the differences in the methods, scopes and evaluated light sources. The main conclusion of the life cycle assessments was the clear dominance of the use stage energy consumption. The environmental impacts of the use were found to be sensitive to the life of the light source and the used energy source. The dominance of the use stage was the clearest in light sources of low luminous efficacy and low manufacturing efforts and when using high-emission energy sources. The manufacturing was usually the second significant cause for average environmental impacts. The importance of the manufacturing is estimated to increase by a more detailed assessment of the manufacturing processes. The average environmental impacts of other life cycle stages, such as transport and end-of-life, were found practically negligible, but possibly notable in a certain environmental impact category.