The pyrolysis of three different biomasses, rice husk (RH), zoita wood sawdust (ZW) and pine wood sawdust (PW), was studied at 500 °C in a multipurpose unit at the bench scale to determine the yields of the different products and the compositions and properties of the liquid products, with particular emphasis given to the alquitranous fractions (tars). It was possible to link the characteristics of the tars with the compositions of the raw biomasses and verify their potential in various applications. The analytical techniques employed in the characterization of biomasses included lignin, celulose and hemicellulose analysis, ultimate and proximate analysis and thermogravimetry–mass spectrometry analysis (TG-MS). Elemental analysis, gas chromatography–mass spectrometry (GC-MS), nuclear magnetic resonance spectroscopy (¹H NMR), Fourier transform infrared spectroscopy (FTIR) and size exclusion chromatography (SEC) were used to characterize the tars. The tar yields were 1.8, 7.4 and 4.0 %wt. in the cases of RH, ZW and PW, respectively. The tars showed higher carbon content, between 60.3 and 62.2 %wt., and lower oxygen content, between 28.8 and 31.6 %wt., than the corresponding raw biomasses. The main components of the tars had aromatic bases, with phenols representing more than 50%. Tar RH included more guaiacols, while Tars ZW and PW included more phenols and alkylated phenols.

This study reports on the design, construction, and operation of a laboratory-scale biomass gasification reactor, together with the procedures used to define and evaluate key operational and performance variables, including piston velocity, nominal biomass residence time, airflow rate, gas yield, lower heating value, and gasification efficiency. The unit is a moving-bed reactor operating in co-current gas–solid mode and reproducing key features of downdraft-like gasification, allowing the identification of the four main reaction zones: drying, pyrolysis, oxidation, and reduction. The reactor exhibits simple operation and handling and, notably, enables controlled axial displacement of the biomass bed through the reaction zone, allowing the nominal solid residence time in the heated zone to be adjusted through piston motion. In addition, the gasification of Spartina argentinensis was investigated in order to evaluate the functionality of the system and to assess reactor performance under selected operating conditions. At operating temperatures of 800–850 °C and an equivalence ratio of 0.2, gas yields exceeded 60 wt%, gasification efficiencies were above 50%, and the product gas reached heating values close to 1000 kcal Nm⁻³, indicating a favorable fuel quality of the product gas. These results confirm the potential of the proposed reactor as a useful experimental platform for the investigation of biomass gasification under controlled laboratory conditions.

The valorization of agro-industrial byproducts through pyrolysis represents a sustainable route for generating multifunctional raw materials within the framework of a circular bioeconomy. In this study, rice husk (RH) and sugarcane bagasse (SCB) were pyrolyzed in a semi-continuous reactor at 500 °C in order to compare product yields and to characterize resulting gas, aqueous and tar fractions. SCB produced the highest bio-oil yield (44.2 wt%), whereas RH generated the highest char yield (42.9 wt%), consistent with its higher ash and lignin contents. In both cases, tar represented about 12 wt% of the bio-oil. Detailed characterization revealed that the liquid products contained oxygenated compounds of interest, mainly carboxylic acids, ketones, and phenols. Acetic acid was the predominant compound in the aqueous phases, while tars were composed mainly of phenols, ketones, furans, and acids. Particularly, phenols accounted for 52.6% and 37.8% of the total chromatographic area in RH and SCB tars, respectively, whereas ketones represented about 10% in both cases. These results show that pyrolysis of agro-industrial residues not only enables energy recovery but also provides liquid fractions enriched in value-added chemicals.