## 1 Introduction  
Timber is generally acknowledged as one of the most effective building materials in terms of environmental sustainability because of its inherent eco-compatibility, mechanical and building physic performance, and ease to install [1, 2, 3]. In the literature, there are numerous studies aimed at evaluating, through Life Cycle Assessment (LCA) approaches, the environmental impact of timber constructions in relation to other materials, especially concrete and steel, with reference to the consumption of raw materials and primary energy, the production of carbon dioxide, and in general the emission of greenhouse gases (GHG) in all phases of the useful life of the material [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. The general result is the lower level of environmental impact of timber, especially considering wood carbon storage capacity. Therefore, the use of timber in construction has recently undergone a great boost, also favored by the development of highly technological construction systems such as laminated timber. If solid timber may have some limitations of use related to the maximum dimensions of the elements, depending on the tree from which they come, and to the presence of natural defects (knots, clusters of knots, resin pockets, etc. ), the use of laminated timber overcomes these limitations thanks to the production process. The production process of laminated timber includes the quality control of the boards for the removal of the elements or portions that have defects higher than the thresholds defined in specific standards, and allows to obtain final structural elements with desired length, thickness, and shape via the phases of butt jointing of the boards, gluing of overlapping boards, and possible curvature. It is therefore an industrial product that entirely overcomes the limitations of solid timber thanks to the technological manufacturing. Like solid timber, laminated timber must be graded to determine its strength and stiffness profile for structural purposes. Generally, grading of component dry boardsis performed first, then the performance profile of the composite laminated element is defined according to boards properties. Boards grading can be carried out through the non-invasive determination of some indicating properties related to the mechanical ones (machine grading): strength, stiffness, and density [16; 17; 18]. In general, the production process of a laminated element consists of many phases: cutting, reduction into boards, drying, grading, jointing and gluing, and finishing processes (trimming, planing, cutting, etc.). Considering the energy required for the various processes that make up the structural timber supply chain, from the forest to the end user, and the related emissions, it is immediately evident that their optimization is important to keep the use of this material sustainable. Given that drying is the most environment-impactful phase of the entire process [19; 20; 21; 22], due to the high energy required to remove moisture from the wood and the possible emission of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) [23], the advantage that would be obtained in drying only the material of proper quality is evident. Discarding wood with inferior properties prior to drying can result in significant cost savings in the drying process. In addition to this, the production of boards for laminated timber is affected by percentages of rejects that can be very high, which, depending on the wood species, can lead to low yields that affect the sustainability of the production. These aspects of the manufacturing process lead to the opportunity of carrying out a pre-grading of the material still in the wet condition, in order to bring to drying only the material suitable for structural uses and to reduce production costs related to low yields at the same time.