Livscykelanalys av ett samverkansbjälklag av KL-trä och betong : åtgärdsförslag för minskade koldioxidutsläpp

Sammanfattning: Purpose: The purpose of this study was that from a life cycle assessment, LCA, present action proposals to reduce the emissions of carbon dioxide of a CLT-concrete composite floor which fulfils the regulations of Swedish National Board of Housing. Method: To be able to present action proposals towards reduced carbon dioxide emissions, literature studies was made on previous life cycle assessment on composite floors with various materials. Document analyses were also performed to establish the structure of the composite floor. Carbon dioxide emission data was collected from suppliers’ environmental product declarations, EPD’s. The collected data was then used to create a life cycle assessment where the greatest emission of carbon dioxide could be identified and furthermore be given action proposals to reduce the emissions. Findings: An increased use of bio based materials in buildings could reduce the carbon dioxide emissions by between 42-100 % depending on if the stored carbon is taken in consideration. By doing this the carbon dioxide emissions is reduced by 87 kg CO2- ekv/m2 opposed to assuming wood to be climate neutral. How this is considered needs to be evaluated in the current standards for LCA. According to the LCA the production stage is the largest contributor for carbon dioxide emissions where the concrete is responsible for the largest amount. By reviewing and comparing Environmental Product Declarations, EPD’s, choices can be made to pick the manufacturer with the lowest environmental effect. A considerable reduction can also be achieved by ensuring that the materials used will be recycled or reused after the end-of-life stage. Implications: With adhesive as shear connector full composite action can be achieved for the floor which leads to that the thickness of the floor can be kept at a minimum which in turn leads to lower material usage. By carefully compare manufacturers EPD’s it can be ensured that the material with the least environmental effect will be chosen. Higher demands should be put on manufacturers to perform thorough EPD’s on their products. Evaluation of current standards for LCA should be done where it is clearer how to view stored carbon in bio based materials and also how carbonation of concrete should be considered since these are great factors of uncertainty during an LCA. What happens to the material after end-of-life should be determined in an early stage of planning since great environmental savings can be made by recycle or reuse materials. The concrete should be crushed and reused as fillings for e.g. road construction after end-of-life to accelerate the carbonation process. Time and money are crucial factors for an LCA and needs to be considered in an early stage of planning. Limitations: The structure of the CLT-concrete composite floor is decided to fulfill the regulations that are set by the Swedish National Board of Housing. These regulations are constantly updated and a change in the structure of the composite floor could become necessary in the future. There was no environmental data to be found on the adhesive used as a shear connector between the CLT and concrete due to the manufacturer considering it to be intellectual property of theirs. This is considered to be a limitation to this study. Keywords: Composite floor, CLT, LCA, EPD, carbon dioxide emission