Slow Pyrolysis as a Method for Biochar Production from Carob Waste: Process Investigation and Products’ Characterization

Abstract

The zero-waste city challenge of the modern society is inevitably addressed to the development of model’s waste-to-energy. In this work, carob waste, largely used in the agro-industrial sector for sugar extraction or locust beangum (LBG) production, is considered as feedstock for the slow pyrolysis process. According to the Food and Agriculture Organization of the United Nations (FAO), in 2012, the world production of carobs was ca. 160,000 tons, mainly concentrated in the Mediterranean area (Spain, Italy, Morocco, Portugal, and Greece). To evaluate the biomass composition, at first, the carob waste was subjected to thermo-gravimetric analysis. The high content of fixed carbon suggests that carobs are a plausible candidate for pyrolysis conversion to biochar particles. The thermal degradation of the carob waste proceeds by four different steps related to the water and volatile substances’ removal, degradation of hemicellulose, lignin and cellulose degradation, and lignin decomposition. Considering this, the slow pyrolysis was carried out at three different temperatures, specifically, at 280, 340, and 400 °C, and the obtained products were characterized. Varying the processing temperature, the proportion of individual products’ changes with a reduction in the solid phase and an increase in liquid and gas phases, with an increase in the pyrolysis temperature. The obtained results suggest that carob waste can be considered a suitable feedstock for biochar production, rather than for fuels’ recovery.

Biochar Particles Obtained from Agricultural Carob Waste as a Suitable Filler for Sustainable Biocomposite Formulations

“…Biochar particles (BC) have been produced using carob waste after syrup extraction, for carob candy production, and slow pyrolysis, for fuel production, as shown in Scheme 1 . The BCP has been produced by slow pyrolysis, as a second level waste after pyrolysis process carried out at three different temperatures, i.e., 280, 340 and 400 °C, as reported in our previous work [ 41 ]. In this work the biochar particles as a result of pyrolysis conducted at 280, 340 and 400 °C are named BC280, BC340 and BC400, respectively.…”

Sustainable Materials Containing Biochar Particles: A Review

“…Slow pyrolysis, conducted in the absence of oxygen, is characterized by slow heating rates and long residence times, as well as atmospheric pressure with an operating temperature that can vary from 350 to 800 °C; the necessary energy to pyrolyze the feedstock is usually provided internally by combusting a portion of the feedstock. The main product is a high-carbon solid char, and the coproducts are watery, low molecular weight liquid and a low energy combustible gas [ 7 , 8 , 9 , 10 ]. Fast pyrolysis, like slow pyrolysis, is conducted in the absence of oxygen with a temperature range between 400 and 600 °C.…”

Recycled (Bio)Plastics and (Bio)Plastic Composites: A Trade Opportunity in a Green Future

“…Moreover, currently published studies propose the preparation of novel char particles, which are mainly composed by carbon atoms at ca. 90%, by slow pyrolyzes processes of biomass and/or agricultural waste, as efficient reinforcement agents for polymers [ 95 , 96 ].…”