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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.

This study attempted to investigate the feasibility of volatile fatty acid (VFA) production from coffee pulp hydrolyse, and further to determine the potential of methanization of both the pre-acidified effluent and the coffee wastewater. The experiments were carried out in 2 completely mixed reactors, each one with a working volume of 4 litres. Coffee pulp was used as substrate in the acidogenic reactor and different mixtures of pulper and wash-water and pre-acidified effluent in the methanogenic one. The acidogenic and methanogenic reactors were operated at an organic loading rate of 5 COD g x l(-1) x d(-1) and 0.5 COD g x l(-1) x d(-1). The total, soluble and VFA's effluent COD concentrations of the acidogenic reactor present average values of 57.75, 17.00 and 13.92 g x l(-1) respectively. Under these experimental conditions, 23% (COD based) of coffee pulp was hydrolysed with a rate of 1.32 gCOD x l(-1) x d(-1) and the soluble fraction was transformed to VFA's with an acidification efficiency of 82%. Total VFA's concentration reached a value of 13.9 gCOD x l(-1), and acetate, propionate, butyrate and valerate represented 52%, 28%, 9% and 11% respectively of the liquid phase COD. In the methanogenic reactor, COD removal and methanization of fresh coffee wastewater, pre-acidified effluent and both combined occur with an efficiency of 85% to 95% respectively, with a characteristic biogas composition of 80% CH4 and 20% CO2. These results show that a humid coffee "Beneficio" processing daily 23 tons of cherry coffee (fresh fruit), equipped with a two stage anaerobic digestion process could generate at least 1,886 CH4 m3 x d(-1). This represents an increase in methane production by a factor 3 to 5 compared to a "Beneficio" using anaerobic digestion only for the treatment of its wastewater.

The urban wastewater treatment plants of the 21st century will have to consider the removal of the carbon, nitrogen and phosphorus. On one hand, the usual exogenous carbon source for tertiary treatment are generally supplied as methanol, ethanol, acetic acid, etc. On the other hand, the anaerobic wastewater treatment plant produces a biogas which contains up to 90 % of methane and which could be used as a cheap carbon source for denitrification. The first step of this work conducted in batch culture with or without copper, has shown that a consortium of methanotrophic and denitrifying bacteria are involved in this process. The methanotrophic bacteria oxidises methane under aerobic conditions via a specific enzyme (Methane Mono Oxygenase) and produces a soluble organic carbon in the liquid phase available for the denitrification. During the batch culture, when dissolved oxygen concentration decreases below 1 mg/l, a maximum denitrification rate of 3.3 mg N-NO3/l.h was obtained with 80 μg/l of copper in the medium. The consumption rate of methane was 3.5 mmol CH4/l.h. The molar ratio of the oxygen/methane consumed was 1.27, and the mass ratio of C-CH4 consumed to N-NO3 eliminated was 10.9. During chemostat culture, denitrification on synthetic and real nitrifying water was tested. The stability of the consortium has been verified under different culture conditions. The variation of the dilution rate showed that the maximum one was 0.16 h−1. The specific denitrification rate obtained with synthetic and real water were respectively 6.1 and 9.47 mg N-NO3/TSS.h, with a C/N mass ratio of 3.6 and 4.6. In chemostat, culture the efficiency of the methane oxidation and the denitrification was improved.

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