It is expected that Cross-laminated timber (CLT) and other engineered wood products will experience rapid growth in the coming years. Global population growth is requiring more housing units, at the same time the negative impact of construction industry cannot stay in the same level as today. Alternatives for concrete and steel reinforced structures are being explored. CLT has proven to be an excellent substitution for concrete regarding construction of buildings up to eight storeys high. In addition to much lower environmental impact, construction process using CLT takes significantly less time due to pre-cut shapes required for specific project. Despite mentioned benefits, there are considerable amount of CLT cuttings generated in this process. Due to irregular shape and small dimensions of these cuttings they are useless for further use in construction. By applying re-processing technology described in this paper, around 70 % of generated cuttings can be re-processed into new CLT panels. In this paper we are evaluating the environmental benefits of re-processing these cuttings into new CLT panels versus business-as-usual scenario with waste disposal. Life cycle assessment results showed significant reduction of environmental impact for the scenario of CLT cutting re-processing.

People have erected buildings with the use of timber structures for a long time. The uses of timber constructions are very diverse—it is used for the production of exterior wall and roof constructions, window frames and doors, and it is used for dry as well as wet premises. Scandinavian countries have extremely vast experience of using timber structures. Latvia has a rather extensive timber processing and timber structure manufacturing sector. Many companies are involved in timber processing, however, to enable even more extensive use of timber structures, environmental and technically economic requirements of contemporary building must be taken into consideration. Environmental requirements for timber structures provide certain advantages in comparison to other building materials, but technically economic requirements are very important as well. The development of manufacturing of glued constructions and research of production processes of these constructions allows one to find solutions for the reduction in the cost of timber structures, and the results of such research can ensure significant development of the use of timber structures in building, as well as reduce total construction costs. The basic objective of the study is to investigate the residual materials arising as a result of processing cross-laminated timber constructions (CLT panels), material generated as a result of high levels of construction production, and research of the opportunities to reprocess the residual materials generated as a result of laminated timber structure manufacturing into materials suitable for production of building constructions. The majority of CLT panels are manufactured using 20, 30 and 40 mm thick boards, and, during the panel manufacturing process, there are various standard thicknesses of panels, for example, 60, 80, 100, 120, 140, 160 mm, etc. Various layers are used for the creation of various thicknesses depending on the necessary technical properties. Various arrangements of the thickness of a single panel will cause different structural and physical behaviour (i.e., impact of changes in moisture, fire resistance, etc.). During the research and for the purposes of testing of CLT panels, only residues with equal types and thicknesses of lamellae were selected. Two main purposes were included in the panel testing process: (1) Comparison of technical performance of the residues of CLT panels with the classic CLT panel. Curve strength and tensile strength tests were performed in accordance with LVS EN standards (LVS EN 16351: 2016 and LVS EN 408 + A1: 2012). All the samples were prepared according to the LVS EN standards. (2) To assess the impact of two resins (melamine urea formaldehyde (MUF) and polyurethane (PU)), widely used in industry, on structural properties of recycled CLT material. Results of the research show that recycling residues of glued wooden constructions may lead to good results, and manufacturing residues of CLT panels may be successfully used in construction and for the reduction in CLT panel manufacturing costs.

Many authors have discussed the paradigm shift in economy from linear to circular. Population growth and climate change caused resource scarcity are the main driving forces of shifting to circularity approach. Although consumers have been slower regarding transitioning to more sustainable economy, production companies are the ones who have felt the scarcity of resources first. In this paper we are exploring cross-laminated timber (CLT) production residue utilization possibilities for new product production and using multi-criteria analysis calculating the most promising recycling alternative from the perspective of companies working with wood as raw material. Data matrix for multi-criteria analysis was constructed from literature analysis gathering data on five criteria: (1) production costs; (2) energy consumption; (3) CO2 emissions; (4) product market price and (5) final product to wood residues ratio. Multi-criteria analysis showed that production of mycelium insulation material is the most promising alternative for CLT production residue recycling.