Integrated microwave drying, pyrolysis and gasification for valorisation of organic wastes to syngas

• Drying of organic waste can be co-integrated with microwave pyrolysis (MIP).
• Moisture promotes the gasification of char and favours gas production.
• There exists an optimal moisture content which maximises the syngas concentration.
• The specific energy efficiency of MIP can be improved at higher scale.

The development of integrated platforms is desirable in order to improve the efficiency of biorefineries. This study deals with an innovative all-in-one thermochemical process (drying, pyrolysis and gasification) based on the use of microwave energy, which could eliminate the need to pre-dry municipal solid waste in order to produce a high quantity of synthesis gas. Depending on the initial moisture content and pyrolysis time, it is possible to obtain different syngas compositions but only during the first 20 min. Beyond this time the syngas composition remains almost constant. In addition, the moisture content was found to improve the volumetric gas production by almost 50%. The energy consumption of this all-in-one process is discussed by comparing it with the scarce information available in the literature concerning the scaling-up of microwave-assisted processes, which may be more cost-effective at a higher scale.

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