# End-of-Life Scenarios for Mass Timber: Assumptions, Limitations and Potentials--A Literature Review
## 1 Introduction  
The global demand to reduce greenhouse gas (GHG) emissions was formalised in the Paris Agreement [1], adopted by 195 parties in 2015. Its goal is to limit global warming to well below 2 \({}^{\circ}\)C, with an aspirational target of 1.5 \({}^{\circ}\)C above pre-industrial levels. Furthermore, the EU Green Deal [2] reinforced Europe's commitment to sustainable development, with the 2030 agenda targeting a 55% reduction in GHG emissions compared to 1990 levels, and achieving climate neutrality by 2050. These policies advocate for circular thinking [3, 4], in contrast to conventional linear models, in both economic and material resource management. According to [PERSON] et al. [5] and [PERSON] et al. [6], circular thinking involves the narrowing down and minimisation of material usage, the slowing down of material usage, the close-loop of material usage, meaning to reuse them again and again if possible, and the use of regenerative materials. The construction industry is a significant contributor to GHG emissions, accounting for approximately 37% of annual emissions [7]. Despite growing recognition of the need to transition toward sustainable practices, the sector faces several challenges. Technological bottlenecks, such as the full implementation of circularity in building materials, hinderprogress. Furthermore, reliance on traditional energy-intensive materials like concrete and steel intensifies emissions. Policy implementation also presents hurdles; while frameworks like the EU Green Deal [2] set ambitious targets, uneven enforcement and varying regional regulations complicate adoption. A lack of standardised metrics for sustainability further complicates decision-making for the construction industry. Therefore, incorporating full Life Cycle Assessments (LCA) into the selection of building materials can help designers and practitioners identify and choose the least impactful options, thereby significantly reducing emissions in building design. LCA, in fact, is the method used to measure the environmental impacts across all stages of a material's life cycle, from raw material extraction, production, and transportation, to construction, operation, maintenance, and finally, demolition and waste management at the end of its service life [8]. The full life cycle of mass timber is illustrated in Figure 1 with all life cycle stages according to EN 15978 [9]. In light of the EU's climate policies, wood and the forestry industry play prominent roles in achieving recently intensified sustainable targets [10]. In recent years, mass timber has gained recognition as an environmentally friendly and sustainable alternative to materials like concrete and steel, especially in large-scale construction. Mass timber, a category of engineered wood products, comprises multiple layers of solid wood bonded together using adhesives, nails, or dowels to create large-scale structural elements such as columns, beams, and panels. Out of the big variety of mass timber products, the most commonly used ones include Cross-Laminated Timber (CLT), Glue-Laminated Timber (GLT or Glutam), and Laminated Veneer Lumber (LVL) [11; 12], the focus of this study. Many studies [13; 14; 15; 16; 17] have highlighted the climate benefits of mass timber buildings compared to those made from fossil-based materials. [PERSON] and [PERSON]'s LCA studies [18] revealed that using Cross Laminated Timber (CLT) instead of conventional construction materials like reinforced concrete (RC) in multi-story buildings could achieve approximately 40% savings in GHG emissions. Approximately 70% of the wood in the European Union is utilised as mass timber for the construction industry today [3]. Given the increasing production, utilisation, and research on mass timber, it is crucial to incorporate LCA (Figure 1), as mentioned earlier, into the discussions of mass timber, particularly at the time of the climate crisis. Special attention should be paid to the assessment of end-of-life (EoL) stage C (Figure 1) for widely used products like CLT, Glutam and LVL.