Microwave pyrolysis of olive pomace for bio-oil and bio-char production

[Display omitted] •Microwave pyrolysis of olive pomace was investigated.•Optimal processing conditions were determined to be 200 W for 180 s.•Energy requirement of 3.6 kJ/g pyrolysed 80% of OP and yielded 30% bio-oil.•Microwave power influenced textural and adsorption properties of bio-chars.•Bio-oils contained a high abundance of acetic acid. Olive pomace is a widely available agro-industrial waste residue in Europe that has the potential to contribute towards a circular, low carbon bio-economy. This study demonstrated, for the first time, the ability to successfully pyrolyse olive pomace with microwaves for the production of bio-char and bio-oil. It was found that the energy requirement needed to pyrolyse up to 80% of the olive pomace was as low as 3.6 kJ/g and bio-oil yields up to 30% were produced. Microwave power did not influence the overall yields or the chemical composition of the obtained bio-oils, but did alter the textural properties of the generated bio-chars and their ability to remove methylene blue dye. Optimum processing conditions were found to be within the 3.6 kJ/g energy requirement with a microwave power of 200 W and processing time of 180 sec. These conditions produced a bio-oil fraction containing mainly acetic acid (71.9%) and a bio-char with a surface area of 392.3 m2/g, micropore volume of 0.15 cm3/g and a methylene blue removal efficiency of 40 qMB mg/g. The results acquired from this study reveal the superiority of microwave heating in a pyrolysis system and highlight a novel and prospective route for added value recovery from natural waste resources like olive pomace.