Assessment of embodied environmental impact on log wooden wall member.

Life cycle assessment (LCA) based on the cradle-to-gate inventories from factory was used to examine the raw material, energy consumption and environment load of embodied process on the functional unit of 1 m³ wall product. Moreover, CML-2001 method and database provided by GaBi were used to evaluate environment impact of wall product in the life circle scope. The results were as follows: 1) six impact categories had been assessed in detail in the LCA study: global warming potential (GWP), human toxic potential(HTP), acidification(AP), eutrophication (EP), photochemical ozone creation potential (POCP), abiotic depletion (ADP) and the absolute values were 3.50×10^-9, 2.11×10^-9, 1.38×10^-10, 1.38×10^-10, 2.33 ×10^-11, 1.30×10^-12, respectively. GWP and HTP were mainly responsible for the preparation of wall product, accounted for 59.2% and 35.7% of total environmental impacts, respectively. 2) To carry out this analysis, a wood factory was assessed in detail and the process was divided into four stages: the raw material obtaining stage, the glued laminated timber preparation stage, the wood wall preparation stage, the painting and packing stage and the absolute values of each stage were 2.40×10^-9, 7.32×10^-10, 4.25×10^-10, 7.20×10^-11, respectively. Raw material obtaining stage was the main stage of environment impacting. 3)Excluding the positive impact of the photosynthesis, HTP was mainly responsible for the environmental deterioration and accounted for 35.7% of total environmental impact. Raw material obtaining, glulam preparation and wall preparation caused the most of HTP. The detailed analysis of each stage identified the most important environmental hot spots of HTP: the wood dust and electricity usage.