## 1 Introduction  
Wood-based panels (WBPs) are important building construction materials widely used for many applications and are comprised of plywood, particleboards, fiberboards, and oriented strand boards, with the most produced and consumed capacity of particleboards (-50% in Europe) [1]. Commercial WBPs are produced from mechanically treated wood bonded by a synthetic adhesive usually containing formaldehyde that is continuously emitted during the exploitation, thus polluting the indoor air quality. A relatively new issue is the profile of volatile organic compounds (VOCs) that are also emitted from WBPs, raising no lower concern than formaldehyde as they contain terpen and aldehydes, e.g., furfural, and organic acids characterized as indoor air pollutants [2]. As formaldehyde was recognized as a human carcinogen [3], the WBP industry was challenged to strictly regulate its level, limiting legislation in all developed countries. No mandatory upper levels are established yet for VOCs from WBP. However, Germany and France were pioneers in their regulation, contributing to the Construction Products Directive [4] and publishing specific regulations followed by Belgium [5]. Another important challenge of the WBP industry is the continuously changing raw material situation due to the global changes in the forest area, high competition, and growing demand for WBP production [1]. Therefore, agricultural lignocellulosicics as nonfood by-products are very attractive from an economic and sustainability perspective for developing particleboards [6], particularly as binder-less boards [7; 8; 9]. This type of board consists of only a selected lignocellulosic that is mechanically processed by shredding and then hot-pressed under certain conditions at which lignin starts to melt and interact with other constituents, resulting in a binder-less composite. To improve the interaction between the constituents of lignocellulosicics, many pretreatments have been studied; steam explosion (SE) resulted in superior physical-mechanical properties of the obtained binder-less boards [10]. However, the SE pretreatment leads to a relatively strong odor even emitted from the obtained binder-less boards independent of raw lignocellulosic species, which raises concern about the use of the boards. From this point of view, raw lignocellulosic species might play a key role as it was demonstrated that spruce strands showed the highest amounts of total VOCs while untreated hemp shive showed the lowest [11]. As a reaction to the industry's challenge related to formaldehyde emission, bio-based adhesives are on the research top, generally comprising lignin, tannins, protein, and starch [12]. A very new and promising bio-based adhesive has been revealed in the form of suberinic acids containing binder from birch wood outer bark [13] investigated for application in particleboard [14] and plywood [15]. However, very few studies have investigated the VOC profiles of binder-less and bio-adhesive-bonded particleboards. It has been reported that pyrolysis bio-oil used to substitute phenol in phenol-formaldehyde resins for producing plywood partially presents greatly increased carcinogenic and non-carcinic risks because of the detected significantly higher emissions of formaldehyde, N,N-dimethylformamide, benzofuran, and furfural [16]. Chemical modification of raw hemp shives with tartaric acid, citric acid, and sodium bicarbonate resulted in an adverse effect, leading to increased total VOC emissions [11]. Higher emissions have been noticed in particleboards bonded with tannin-based adhesives vs. urea-formaldehyde adhesive [17]. Thus far, only two works have been reported about VOC profiles from SE materials of softwood bark pellets, revealing the potentially problematic emissions [18; 19].