AUTOCLAVING OF WASTE PLASTIC-FREE PAPERS FOR RESOURCE RECOVERY AND REUTILIZATION

The ultimate goal of sustainable material management (SMM) is maximal recycling and reuse with minimal waste. The autoclaving (or cooking) of the mechanical heat treatment (MHT) is one of the alternatives for pre-treating the municipal solid waste (MSW) prior to further separation and recycling to achieve the SMM. After autoclaving, the dry-basis mass of MSW decreases while the plastics are softened and shrunk. Therefore. the MSW after autoclaving can be properly separated into different fractions such as metals, plastics, compost-like and organic fibre for reutilization. The organic fibre can be further processed and upgraded to produce refuse derived fuel or bio-char of high quality. Three commonly used plastic-free papers, namely, toilet paper, newsprint paper and thick plate paper were autoclaved to assess their key characteristics after autoclaving. The weight changes of combustibles, lignin, cellulose and hemicellulose of target papers after autoclaving with saturated steam at 155 and 180 degrees C were examined. The results show that a higher temperature leads to a higher extent of hydrolysis and cracking reactions, resulting in a dry-basis weight reduction of paper as well as combustibles. The hemicellulose is hydrolyzed and cracked via the autoclaving easier than the cellulose. Although a small amount of mass is lost after autoclaving, however, the dry-basis heating values of target papers are retained. The destruction of hemicellulose would make the fibre structure more fragile and easier for grinding and pelleting. The information obtained in this study is useful for the rational design and proper operation of autoclaving system for treating the used plastic-free papers.