This research work involved the production of aspen OSB panels in a pilot plant using three types of commercial adhesive systems respectively as a wood binder (PF, PF/MDI and MDI). It was demonstrated that spraying urea aqueous solution to dry wood strands at 0.2% and 0.5% urea loading rates (urea solids on a dry wood weight basis) can effectively reduce the emissions of formaldehyde, acrolein and some other volatile organic compounds from OSB pressing without adversely affecting the board properties regardless which type of adhesive is used. The side-effect of the urea addition was the dramatic increase of press emission of nitrogen compounds, most likely due to the slow decomposition of urea to ammonia at high press temperatures. This approach may also be effectively and economically applied to lowering formaldehyde, acrolein and VOC emissions from OSB dryer and the side-effect of increased nitrogen compounds emission could be less due to lower wood temperatures inside the OSB dryer than those inside the OSB press.
It was also demonstrated that using MDI adhesive to partially or completely replace PF adhesive can lower formaldehyde, phenol and total VOC emissions from OSB pressing. Under the test conditions of this work and without urea addition, the MDI-bonded aspen OSB panels emitted about 87% less formaldehyde, 80% less phenol and 25% less water-soluble VOC than the PF-bonded aspen OSB panels. The PF/MDI-bonded aspen OSB panels emitted about 61% less formaldehyde, 41% less phenol and 11% less water-soluble VOC than the same PF-bonded panels. However, the MDI-bonded panels produced 65% higher water-insoluble VOC than that of the PF-bonded panels although the water-insoluble VOC accounted for less than 3% of the total VOC emitted from the MDI-bonded panels.