The municipal solid waste (MSW) can be made as refuse derived fuel (RDF) for power generation or steam production. However, the complexity and variation of composition of components make the MSW and RDF become low grade fuels which result in unsteady combustion and high pollution emission. In Taiwan, there are over 40 wt.% organic fiber in the reclaimed MSW, including un-recycled paper and garden waste. These organic fibers are biomass. The present study has assessed the performance of mechanical heat treatment (MHT) of MSW, aiming at the feasibility of recovery and reutilization of organic fiber. The MHT consists of autoclaving and mechanical separation.The pretreatment of MSW via autoclaving greatly assists its further separation and reutilization. After autoclaving process, the properties of constituents of MSW are significantly changed. For example, the mass decreases while the volume density increases and the plastic constituents are softened and shrunk. Thus, the energy density per unit volume increases 1.5 to 3 times. Therefore, the MSW after autoclaving can be properly separated into different fractions such as metals, plastics, compost-like and primary RDF or bio-char for further reutilization.
In this study, a 530 L batch autoclave reactor was used to treat the wastes with steam. The target wastes are MSW, garden waste, waste paper, plastic waste and kitchen waste. The results indicate that the most suitable conditions for autoclaving MSW are at 155 ℃ and 30 min. Without counting the heating value of input waste, the energy return on investment (EROI) of MSW via autoclaving process is 1.5. The results show that the use of reused down-stream steam from incinerator for the autoclaving process of MSW can offer a better beneficial use of energy, achieving better carbon reduction.