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.