Utilization of mixed organic-plastic municipal solid waste as renewable solid fuel employing wet torrefaction.

The largest obstacles in the utilization of municipal solid waste (MSW) as solid fuel in developing countries such as Indonesia are its high water content, irregular size and shape, and difficulty-to-sort due to the mix of plastic and organic waste. Based on literature study, wet torrefaction could be an appropriate pre-treatment process for mixed MSW because it requires no initial drying and mixed organic-plastic MSW can be processed without initial sorting. In this research, experiments were conducted to investigate the effect of wet torrefaction on increasing the fuel properties of mixed MSW. Based on field survey, the composition of the analyzed sample was: leaf litter (34.67%), food waste (23.33%), vegetable waste (14.33%), fruit waste (11.00%), and non-recycled plastic (16.67%). The experiments were conducted in a 2.5-L stirring reactor temperature variation (150, 175, 200 and 225 °C) with several holding times and solid loads. The result showed that wet torrefaction at a temperature of 200 °C with holding time of 30 min and solid load of 1:2.5 was the optimum condition, producing solid product with uniform physical shape, small particles and homogeneous particle size distribution, HHV of 33.01 MJ/kg and energy yield of 89%. The wet torrefaction process is not only suitable to convert the mixed MSW into renewable high energy density solid fuel, but it can also be used to produce separate organic product that can be used as solid fuel and plastic product that can be prepared for other treatments, such as pyrolysis to produce liquid fuel or recycling.

Municipal solid waste processing and separation employing wet torrefaction for alternative fuel production and aluminum reclamation.

This study employs wet torrefaction process (also known as hydrothermal) at low temperature. This process simultaneously acts as waste processing and separation of mixed waste, for subsequent utilization as an alternative fuel. The process is also applied for the delamination and separation of non-recyclable laminated aluminum waste into separable aluminum and plastic. A 2.5-L reactor was used to examine the wet torrefaction process at temperatures below 200°C. It was observed that the processed mixed waste was converted into two different products: a mushy organic part and a bulky plastic part. Using mechanical separation, the two products can be separated into a granular organic product and a plastic bulk for further treatment. TGA analysis showed that no changes in the plastic composition and no intrusion from plastic fraction to the organic fraction. It can be proclaimed that both fractions have been completely separated by wet torrefaction. The separated plastic fraction product obtained from the wet torrefaction treatment also contained relatively high calorific value (approximately 44MJ/kg), therefore, justifying its use as an alternative fuel. The non-recyclable plastic fraction of laminated aluminum was observed to be delaminated and separated from its aluminum counterpart at a temperature of 170°C using an additional acetic acid concentration of 3%, leaving less than 25% of the plastic content in the aluminum part. Plastic products from both samples had high calorific values of more than 30MJ/kg, which is sufficient to be converted and used as a fuel.