Dra. Azócar-Ulloa, Laura

Nowadays, leaves, bark, and branches are generated from the tree-pruning process in urban places, where their management is a problem because of the necessity of disposal. These wastes are lignocellulosic biomasses with poor properties for use in biofuel production, but with interesting projections for building block products such as phenol compounds. Therefore, extensive biomass characterization of urban pruning from Liquidambar styraciflua L. was developed to evaluate its composition as a tool for phenol production through thermal processing, in which solvent extraction is a complementary tool for selectivity improvement. The results showed high lignin content in bark and leaves at 45 and 28 %, respectively, compared with that in branches (14 %). Additionally, high extractives in leaves (14 %) could be an additional source of phenols. The lignin units were analyzed by Raman dispersion, revealing p–hydroxyphenyl (H) units in the bark, guaiacyl (G) units in the bark and leaves, and syringyl (S) units only in the branches. Furthermore, the micropyrolysis coupled with gas chromatography/mass spectrometry assay realized at 600 ◦C showed high presence of phenolic compounds in the three biomass investigated, where a high phenol concentration was identified in leaves, probably due to the S unit degradation during pyrolysis. With these results, an assay for bio-oil production was performed in a low-temperature pyrolysis reactor using leaves as feedstock, reaching a low bio-oil yield with high water content favored for the high inorganic content of leaves (13 %). The produced bio-oil was used for liquid–liquid extraction evaluation, where 1-octanol and methyl isobutyl ketone were identified as interesting solvents for catechol and phenol extraction, respectively. This article presents the challenge of characterizing each part of urban trees, which could be a tool to promote the use of urban pruning by studying the thermal degradation mechanism to implement processes for high-value products, such as phenols produced from L. styraciflua L.

The carbonization of Nannochloropsis gaditana microalgae biomass was found to produce bio-coal that is similar to bituminous coal used in thermal power plants. Currently, microalgae that capture CO2 while they are in the growth stage are considered a source for the production of biofuels. The carbonization of biomass for producing bio-coal has received attention for its ability to improve the biomass quality for producing solid biofuels. The research was focused on optimizing a fixed carbon index (FCindex), which allows finding operational conditions of carbonization to favor the fixed carbon content without significantly affecting the bio-coal yield. The optimization carried out by response surface methodology in a thermogravimetric analyzer allowed the prediction of optimal carbonization conditions to achieve an FCindex of 191% at 403 °C, 71 °C/min, and 60 min of residence time. The bio-coal produced under optimized conditions was characterized by 59% of fixed carbon and 41% of volatiles on a dry and ash-free basis, which is similar to bituminous coal. The promising results of dry carbonization producing bio-coal similar to bituminous coal could promote this technology, avoiding the necessity of hydrothermal carbonization. Because a high ash content was detected in the final product, further studies using the optimized conditions and a washing step should be conducted.