Simulation and multi-objective optimization of argan residues slow pyrolysis for polygeneration of bio-oil, biochar, and gas products

Argan oil extraction yields three byproducts that are traditionally harnessed. Conventional combustion of argan residues is environmentally unfriendly and inefficient, driving our exploration of pyrolysis as a more promising alternative. This technology yields bio-oil, serving as a resource for heating, power generation, and chemicals. Biochar, for wastewater treatment, soil improvement, and serves as solid fuel. The gas is utilized for heating, electricity generation, and chemical synthesis. The novelty of this study lies in optimizing slow pyrolysis conditions to simultaneously maximize these three key products derived from the pyrolysis of argan residues. To achieve this goal, a suitable and versatile simulation process was developed. Initially, the model was validated with relative errors around 10 % compared to literature experiments. Then, a distinctive methodology was employed, involving response surface methodology to generate nine empirical models, where holding time and temperature effectively explain product yield variation. The best optimal parameters were objectively determined by combining a non-dominated sorting genetic algorithm to multi-criteria decision-making methods. The study identified that the best pyrolysis conditions for all three argan residues are temperatures between 470 and 490 degrees C, with no holding time at the final temperature. For argan shells, press cakes, and pulps, the obtained maximum bio-oil yields were 25.45 %, 23.40 %, and 19.19 %; biochar yields were 37.99 %, 36.33 %, and 38.97 %; and gas yields were 36.56 %, 40.27 %, and 41.85 %, respectively. These finding highlights that argan residues can be successfully valorized at less demanding pyrolysis conditions, making their pyrolysis in rural areas more feasible, efficient, and ecofriendly.