Keywords: extender, filler, formaldehyde emission, Nicotiana tabacum L., nicotine, plywood, tobacco The study investigated the use of native type (Batek) tobacco (Nicotiana tabacum L.) stalk particles from two different mesh sizes – passing 100 mesh but retained at 200 mesh coded as N-100m (74–149 µm) and passing 200 mesh coded as N-200m (< 74 µm) – as additive with both extender and filler property, as well as formaldehyde scavenging property in urea-formaldehyde (UF) resins adhesive formulation used to bond veneers [Falcataria moluccana (Miq.) Barneby & J.W. Grimes] into plywood. The effect of tobacco stalk particle (TSP) size on adhesion performance, tensile shear strength (TSS), and wood failure (wF), as well as formaldehyde emission (FE) of three-ply plywood, was investigated and compared with traditional additives such as wheat flour (WF), coconut shell flour (CS), and rice hull flour (RH). The glue-mix containing UF resins with TSP at 8% by mass was blended very well. There is no difference in the TSS and wF of plywood bonded with N-200m TSP as additive compared to commercial UF formulations; however, a significant decrease of TSS and wF was observed with N-100m. The addition of N-200m significantly reduced FE by 23%, 33%, and 44% compared to those of WF-CS, WF-RH, and N-100m, respectively. Philippine Journal of Science 149 (2): 363-372, June 2020 ISSN 0031 - 7683 Date Received: 07 Dec 2019 Juanito P. Jimenez Jr. 1,2 , Menandro N. Acda 2 , Ramon A. Razal 2 , Willie P. Abasolo 2 , Hidelisa P. Hernandez 3 , and Arnold R. Elepaño 4 1 Department of Science and Technology Forest Products Research and Development Institute College, Laguna 4031 Philippines 2 Department of Forest Products and Paper Science 3 Institute of Chemistry; 4 Institute of Agricultural Engineering University of the Philippines Los Baños College, Laguna 4031 Philippines Effect of Tobacco Stalk Additive Particle Size on the Bond Strength and Formaldehyde Emission of Urea Formaldehyde Bonded Plywood INTRODUCTION Tobacco (Nicotiana spp.) is one of the highly valued crops in the world that provides job to farmers in rural areas and contribute significantly to the national economy of many countries (Rodgman and Perfetti 2013). It is an annual plant with a stalk height that ranges from 0.8–2.5 m and contractually grown for the cigarette manufacturers by the *Corresponding Author: jpjimenez4@up.edu.ph juanito.jimenez@fprdi.dost.gov.ph farmers for its high-grade quality leaf (NTA 2019). The harvesting of mature tobacco leaves involves cutting them off from the fibrous stalk. In the Philippines, about 900 kg/ha of tobacco stalks are either left to rot on the ground, burned in the field, or used as household fuel [Roberto R. Bonoan, National Tobacco Administration (NTA), pers. comm. 2018]. Considering the large volume of tobacco stalks, it is worthwhile to process them into additives for plywood adhesive to add value and provide an additional source of income for the farmers. 363