Influence of the microwave absorbent and moisture content on the microwave pyrolysis of an organic municipal solid waste

• Microwave pyrolysis of MSW has great potential for the production of synthesis gas.
• The presence of a microwave absorbent is mandatory to carry out the pyrolysis.
• A minimum absorbent-to-waste ratio of 0.2:1 has been found needed to induce pyrolysis.
• The moisture content of the MSW increases gas yield and favours syngas production.

Microwave pyrolysis is presented in this study as a recycling approach for municipal solid waste treatment. The process is based on the conversion of solid waste to syngas (CO + H2) by means of a microwave absorbent. Experiments to characterise the syngas produced were performed using the char obtained from the pyrolysis of a municipal solid waste as microwave absorbent in the microwave power range of 150–450 W and in an absorbent-to-waste ratio range of 0.2:1 to 1:1 (wt.%:wt.%). A rich-syngas fraction with a high H2 content (c.a. 50–55 vol.%) was obtained and analysed by means of response surface methodology through the interaction between the microwave power and absorbent-to-waste ratio. Moreover, a positive effect of the moisture content on gas production is attained since gasification of the char occurs. Thus, the simple use of a cheap waste-derived char leads to a reduction in the microwave power and economic cost of the process.