Waste-to-BioEnergy pathway for waste activated sludge from food processing industries: An experiment on the valorization potential under CO2 and N2 atmospheres through microwave-induced pyrolysis

[Display omitted] •Microwave pyrolysis successfully reduce the mass of waste activated sludge by 80 wt%.•CO2 pyrolysis improves CO generation in the gaseous product (up to ∼ 50 vol%).•CO2 pyrolysis produce biochar with higher energy density profit (11–14%).•N2 pyrolysis improves H2 generation in the gaseous product (up to ∼ 29 vol%).•Up to 83.2% of the energy stored within the waste can be retrieved in bioenergy form. Pyrolysis is a green and effective method for converting various waste streams into products with bio-energy potential. Waste activated sludge (WAS) from industries requires post-treatment before disposal and will cause serious pollution if not managed properly. Pyrolysis is a viable method for converting WAS into higher-value bio-products. This is the first study to use a lab-scaled microwave reactor to analyse WAS from a food processing and manufacturing company's wastewater treatment plant. The goal is to compare bioproduct formation under various N2 and CO2 atmospheres in order to analyse the WAS waste-to-bioproduct transformation pathway. Result revealed that CO2 pyrolysis on WAS tends to: 1) increase water formation (∼19 wt%), 2) produce biochar with higher energy density profit (∼14%) and 3) generate gaseous products with a higher CO proportion (∼50 vol%). WAS pyrolysis under N2 atmosphere showed 1) an overall better energy profit (