A Life Cycle Assessment of the Environmental Impacts of Cross-Laminated Timber

Sammanfattning: Negative environmental impacts generated by new buildings and the built environment needs to be reduced in order to contribute to mitigation of anthropogenic global warming. Sustainable building certifications such as Miljöbyggnad and DGNB was introduced as a measure to transition into more sustainable buildings. The research study explores the environmental impacts of cross-laminated timber and the differences and effects in life cycle assessment of construction material in Miljöbyggnad 3.0 and DGNB. In addition, to study the impact of carbon sequestration for cross-laminated timber. The construction sector is taking measures to reduce environmental impacts from construction materials and consider increased use of alternative construction materials, such as cross-laminated timber. Cross-laminated timber is considered a versatile, renewable and sustainable structural construction material. The global warming potential is significantly reduced for cross-laminated timber if carbon sequestration, atmospheric carbon being stored in bio-mass, is accounted for. To minimize resource consumption, a circular approach regarding construction material and construction waste is necessary. Waste management is important for the overall environmental sustainability performance of buildings. There are three types of waste disposal, generally defined as either reuse, recycling or disposal. The environmental impacts for construction materials heavily depend on the chosen waste disposal scenario. Regarding cross-laminated timber, possible waste disposal scenarios is reuse, partial recycling and incineration with or without energy recovery. The most environmentally beneficial waste disposal scenario for cross-laminated timber is reuse while the worst is incineration without energy recovery. Cross-laminated timber shows the most environmental beneficial values for five out of the seven assessed environmental impacts in the DGNB life cycle assessment tool, compared to steel and concrete. The global warming potential is lower for cross-laminated timber regardless if carbon sequestration is included, for most waste disposal scenarios compared to steel and concrete. Identified differences in the life cycle assessments between Miljöbyggnad 3.0 and DGNB are the level of complexity, the number of included life cycle phases and assessed environmental impacts. An inclusion of carbon sequestration in a life cycle assessment will drastically decrease the global warming potential for cross-laminated timber.