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

Abstract

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 m 2 /g, micropore volume of 0.15 cm 3 /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.

Impact of Emerging Technologies on Virgin Olive Oil Processing, Consumer Acceptance, and the Valorization of Olive Mill Wastes

“…In a recent study, MW technology was introduced to the pyrolysis process [ 90 ] and found to greatly enhance the loss of mass. When applying less energy (between 0.88 and 1.94 kJ/g), the mass loss increased with MW power, and the highest yields of bio-oil were achieved with the lowest input of 150 W. With higher energies (from 2.27 to 3.27 kJ/g), the maximum bio-oil was obtained at 450 W. Overall, the 150 W power input generated the greatest mass loss and bio-oil yields of the pyrolysis process.…”

Circular Bio-economy—Paradigm for the Future: Systematic Review of Scientific Journal Publications from 2015 to 2021

“…Pyrolysis has been the technology of choice, for olive mill solid wastes (OMSWs) in [70] and [27] and for eucalyptus wood fines in [89], to yield bio-oil and biochar, the former thereafter being valorised to a whole range of platform chemicals. Alternately, by subjecting OMSWs to thermal pre-treatment followed by anaerobic digestion, phenol and biomethane can be obtained [124].…”

Available Pathways for Operationalizing Circular Economy into the Olive Oil Supply Chain: Mapping Evidence from a Scoping Literature Review

“…Besides pyrolysis-based systems, the biochar can be obtained from biomass gasification at high temperatures (>700 • C), by means of microwave heating [96], or from a novel technology that integrates pyrolysis with downstream post-catalytic reforming of its volatile products: thermocatalytic reforming (TCR) process [14].…”