Hydrothermal recycling of waste and performance of the recycled wooden particleboards

https://doi.org/10.1016/j.wasman.2006.11.016Get rights and content

Abstract

Recycling today constitutes the most environmentally friendly method of managing wood waste. A large proportion of the wood waste generated consists of used furniture and other constructed wooden items, which are composed mainly of particleboard, a material which can potentially be reused. In the current research, four different hydrothermal treatments were applied in order to recover wood particles from laboratory particleboards and use them in the production of new (recycled) ones. Quality was evaluated by determining the main properties of the original (control) and the recycled boards. Furthermore, the impact of a second recycling process on the properties of recycled particleboards was studied. With the exception of the modulus of elasticity in static bending, all of the mechanical properties of the recycled boards tested decreased in comparison with the control boards. Furthermore, the recycling process had an adverse effect on their hygroscopic properties and a beneficial effect on the formaldehyde content of the recycled boards. The results indicated that when the 1st and 2nd particleboard recycling processes were compared, it was the 2nd recycling process that caused the strongest deterioration in the quality of the recycled boards. Further research is needed in order to explain the causes of the recycled board quality falloff and also to determine the factors in the recycling process that influence the quality degradation of the recycled boards.

Section snippets

Introduction – The need to recycle wood

Today’s rapid technological growth has led to dangerous degradation of the environment, which constitutes a serious threat for upcoming generations. Environmental pollution, the reduction in natural resources and the general disturbance of the ecological balance constitute problems that should be taken into serious consideration by our society (Lykidis and Grigoriou, 2005).

The increase in CO2 and CH4 emissions, resulting from the over-consumption of fuel, from forest fires and from the

The recycling of wood products

The current strategies in managing wood waste and their impact on the environment are presented in Table 1 (European Commission, 1997). Landfilling of organic material leads to CH4 emissions, which result in greenhouse gas potential 21 times higher than that of CO2 (European Cooperation in the field of Scientific and Technical Research, 2002). Furthermore, Risholm-Sundman and Vestin (2005) reported that during the combustion of particleboard it is important to have the appropriate conditions;

Aim

The aim of the present research was to investigate the properties of recycled particleboards made from recovered wood particles. For the recovery of the wood particles, four different particle-recovery hydrothermal treatments were utilized. This applied particle-recovery method differed from other related methods (Moeller, 1993, Boehme and Michanickl, 1998, Michanickl and Boehme, 2003, Riddiough and Kearley, 2001, Riddiough, 2002, Hesch, 2002) due to the fact that during the recycling process,

Materials and methods

For the purposes of this research, one-layer laboratory particleboards with dimensions of 350 × 300 × 12 mm and with a nominal density of 0.65 g/cm3 were manufactured. The wood particles used were obtained from a particleboard manufacturer and produced by chipping poplar, fir, pine and waste wood. In order to minimize potential fine material loss, which would alter the results during the production of the boards, the particle fraction of k < 1.5 mm was removed. A commercial liquid urea–formaldehyde (UF)

Results

The results concerning the bulk density and fraction analysis of the recovered wood particles are presented in Table 2. The recovered particles showed higher levels of k < 1 mm in comparison with the original (control) material, which probably means that the recycling process involves a slight reduction in wood particle size. The reduction in particle size can degrade some mechanical properties of the panels (mostly modulus of rupture). In most cases, the recovered material, when compared to the

Conclusions

Particleboards produced from steam-recovered wood particles showed a quality (with the exception of the modulus of elasticity in static bending and the formaldehyde content) inferior to that of particleboards made from original particles (control). The 2nd recycling process caused further quality degradation in the boards compared with the 1st recycling process. Among the four hydrothermal treatments applied for particle recovery, the treatment of 6 bar/156 °C/45 min resulted in the strongest

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      Comparing these results with the literature is difficult since, to our knowledge, no article reports results concerning ammonia and formaldehyde released in the gas phase. All references dealing with the hydrolysis of UF resin (Myers and Koutsky, 1990; Ringena et al., 2006; Park and Jeong, 2011; Park and Causin, 2013; Lubis and Park, 2018; Grigsby et al., 2014), wood waste such as Particleboard (Lykidis and Grigoriou, 2008; Wan et al., 2014), and MDF (Wan et al., 2014; Hagel and Saake, 2020; Lubis et al., 2018, 2020; Kraft and Roffael, 2003; Grigsby et al., 2014) present analyzes of the hydrolysate in the liquid phase. Some studies carried out in the liquid phase were at atmospheric pressure and not under pressurized steam (Lykidis and Grigoriou, 2008; Wan et al., 2014; Hagel and Saake, 2020).

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