A methodical approach for systematic life cycle assessment of wood-based furniture

Existing life cycle assessment (LCA) studies for furniture focus on single pieces of furniture and use a bottom-up approach based on their bill of materials (BOM) to build up the data inventories. This approach does not ensure completeness regarding material and energy fluxes and representativeness regarding the product portfolio. Integrating material and energy fluxes collected at company level into product LCA (top-down approach) over-rides this drawback. This article presents a method for systematic LCA of industrially produced furniture that merges the top-down approach and bottom-up approach. The developed method assigns data collected at the company level to the different products while, at the same time, considering that wood-based furniture is a complex product. Hence, several classifications to reduce the complexity to a manageable level have been developed. Simultaneously, a systematic calculation routine was established. The practical implementation of the developed method for systematic LCA is carried out in a case study within the German furniture industry. The system boundary was set in accord with the EN 15804 specification cradle-to-gate-with-options. The analysis therefore includes the manufacturing phase supplemented by an end-of-life scenario. The case study shows that the manufacturing of semifinished products (especially wood-based panels and metal components) as well as the electric energy demand in furniture manufacturing account for a notable share of the environmental impacts. A sensitivity analysis indicates that up to roughly 10% of the greenhouse gas emissions are not recorded when conducting an LCA based on a BOM instead of applying the developed approach.