“Characterization of bio-oil and bio-char produced by low temperature microwave assisted pyrolysis of olive pruning residue using various absorbers"

Olive pruning residue is largely formed during cultivation and it is usually disposed through open air combustion directly in the field, but this habit is a possible font of pollution. Pyrolytic conversion of olive pruning residue has been run in a new and very appealing way using microwave as a heating source and different microwaves absorbers in a multimode batch reactor. In this way olive residue was converted into interesting bio-chemical products with short pyrolysis time from 15 to 36 min and peak temperature ranging from 450 K to 705 K according to the different microwave absorber. A very efficient and selective system was realized able to address the process towards the formation of large amount of bio-char (up to 61.2 %) or a high formation of bio-oil (56.2 %) and gas (41.7 %) with a very low formation of bio-char (2.1 %). However when carbon and iron were used as microwave absorbers it was possible to obtain an intermediate amount of bio-char (26-30%) and bio-oil (40 wt %). Bio-oils were collected as dark brown liquids with low viscosity and density. A bio-oil with a low water concentration was obtained using carbon or iron as microwave absorber. Bio-oils formed in all experiments contain a very large amount of acetic acid, even when NaOH was the MW absorber. Furthermore a large amount of aromatics was present in the bio-oil obtained using carbon as MW absorber.