Tree adaptation to environment has been extensively studied. However, little is known about the variations in structure and chemical composition of lignocellulosic biomass (LB) in relation to altitudinal gradient. We wonder, are there significant variations in the LB in the wood across an altitudinal gradient? To answer this, we carried out a study of Abies religiosa. Wood samples were collected from 36 trees, grown between 3000 and 3500 masl, and then subjected to gravimetric and FTIR (Fourier Transform Infrared) spectroscopic analyses. The gravimetric results showed a proportion of 54.81 ± 2.20 % cellulose, 12.37 ± 1.33 % hemicellulose and 24.68 ± 1.16 % of insoluble lignin. Using the principal components analysis with analysis of variance (ANOVA), significant differences were found at 3100 and 3200 masl in two independent components related to both hemicellulose and lignin, through gravimetry as well as the spectroscopic bands assigned to the carbonyl groups of these polymers, respectively. However, the observed changes in chemical composition of LB did not follow a linear relationship with respect to the altitudinal gradient, which suggests that complex environmental interactions could also be playing an important role. Also, there were significant differences (p \ 0.05) in two of the empirical indexes calculated from the FTIR analysis.

Mexico is one of the largest agricultural producers in Latin America and generates a large amount of agricultural residue. The aim of this study was to establish the usefulness of four of the main Mexican crops (corn, wheat, sugarcane, and Agave) as feedstock for lignocellulosic bioethanol production. The lignocellulosic residue ratio (RR), defined as weight of residue (in tons) per ton of product, was measured by sampling crop fields in 11 geographic regions of Mexico. The chemical composition, assessed by Fourier-transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance ( 13 C NMR), and structural composition (extractives, cellulose, hemicellulose, and lignin contents), heating value, and metal content of these lignocellulosic residues were measured. Biorefinery locations, and their theoretical bioethanol production, were suggested using the gravity center method and techno-economic criteria. The highest RR (1.1 ton of straw per ton of grain) was obtained for wheat straw followed by corn 1144

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