Boosting circular economy and closing the loop in agriculture: Case study of a small-scale pyrolysis–biochar based system integrated in an olive farm in symbiosis with an olive mill

Abstract

Carbon sequestration and soil quality improvement coupled with bio-energy generation are important issues to be addressed in agriculture by valorising crop residues and by-products. The aim of this work is to study a pyrolysis–biochar system applied to an olive farm in symbiosis with a 2-phase olive mill. The set-up of a closed-loop productive system is proposed. The results have shown that the valorization of 70.0t of solid and semi-solid wastes issued from both 10ha olive grove and milling process can be converted via pyrolysis into 13, 11, 12t of liquid fuel, biochar and gas fuel, respectively. The liquid and gas fuels can fulfill the olive milling energy needs and produce an electricity surplus of ~13.00MWhel resulting in an extra income (4000€) if sold to the grid. In the case of solar drying of the raw material, ~30.00ΜWhel could provide 8900€ per year. A SWOT analysis shows that pyrolysis of agri-residues targeting biochar can fulfill the aim of closing the loop in agriculture and circular economy objectives.