Exploring the potential of chemical recycling of waste medium-density fiberboards (MDF) under oxidative and pyrolytic conditions

Abstract

Medium-density fiberboards (MDFs) have been widely used to replace natural wood in structural and non-structural applications (mostly in furniture). On the positive side, the use of MDF has certainly reduced the level ofdeforestation. However, there is a need to develop a safe and effective treatment method for waste MDF as the presence of chemical additives in MDF and the generation of fine wood dust pose environmental and health challenges. Thermal decomposition of MDF taps into the “waste-to-energy” approach that has been broadly utilized in the disposal of organic-based wastes. Along this line of inquiry, this study entails three aims; (i) to compute thermodynamics and kinetic functions that govern the decomposition of MDF at conditions encountered at real pyrolytic and combustion conditions in waste incinerators; (ii) to acquire the temperature-dependent profiles of decomposition products; and (iii) to report ultimate and proximate analyses of MDF. Under both pyrolytic and combustion conditions, the thermal decay of MDF exhibits three stages that reflect its structural composition. Pertinent thermo-kinetic parameters were computed using model-fitting and iso-conversational formalisms. The nitrogen content in MDF peaked at 6.3%; significantly higher than that of natural wood (i.e., 1%) and originated from the use of urea formaldehyde resin. Chemical analysis indicates that nitrogenated (i.e., N,N-Dimethylacetamide) and oxygenated (i.e., catechol) products dominate the composition of the non-condensable fraction upon pyrolysis and oxidation of MDF. Such a finding calls for the importance of a post-treatment catalytic process that converts N- and O-containing products into pure hydrocarbons. The high nitrogen content in char of MDF indicates its potential utilization as soil nutrients. Values and insights reported herein are to establish a technical foundation for a biorefinery or a thermal facility that uses waste MDF as a feedstock.