Aims: This work highlights the influence of the additivity of withdrawing electronic groups attached to the aromatic ring on the inhibition of the production of methane gas by the methanogenic bacteria acetoclastic. Study Design: Anaerobic digestion of pig manure, anaerobic toxicity essay, Effect of additivity and the number of electron withdrawing groups on the methanogenic toxicity, relationship between the methanogenic toxicity, electron and steric effects.

In this work, a semi-empirical approach correlating the values of methanogenic toxicity of 22 aromatic compounds was used.  TheIC50 exp, along with the various molecular properties of these compounds were determined using the DFT B3LYP/6-31G (d,p) method. While a conceptual approach of the FDT, was made in order to determine those, which are responsible of this methanogenic activity of the studied aromatic compounds. The Principal Component Analysis method was used in order to describe all the connections and information contained between these various variables (IC50exp.and molecular properties) of the aromatic compounds. TThe Hierarchical Cluster Analysis helped to classify the studied aromatic compounds in various classes defining the various types of methanogenic toxicity. The findings show that the electron withdrawing and lipophilic substituents made the aromatic ring more toxic than the electron donating and hydrophilic substituents.The aromatic compounds with -NO2 and –Cl groups formed the classes of the most toxic with the bactericidal action ofstudied aromatic compounds, with values of IC50exp ranging between 4.19 ± 0.01 and 67.20 ± 1.97 mg/L. The compounds with -OH and -NH2 groups formed the class of the least toxic of studied aromatic compounds with bacteriostatic action with values of IC50exp ranging between 966.27 ± 7.04 and 3151.49 ± 5.93 mg/L. The benzene (aromatic ring unsubstituted) taken as reference, formed its own class with a value of IC50exp of 208.78 ± 2.80 mg/L. It thus marks the line of demarcation between the classes of studied aromatic compounds with the electron withdrawing and/or lipophilic substituents  (-NO2 and -Cl), more toxic with the bactericide action, and that of the aromatic compounds with electron donating and hydrophilic substituents (-OH and -NH2), less toxic with the bacteriostatic action.

Optimal scale production of biogas from the anaerobic digestion (AD) of organic wastes (OWs) as substrates has become one of stimulating environment-friendly procedures to foster the replacement of fossil energies by renewable ones. AD of OWs generated from households is desirable as an effective method to fight against environmental pollution effects of the latter in developing countries. Notably in Africa where each year there are more than 600,000 premature deaths following the use of solid biomass energy (especially charcoal). Yet, if assessing the potential of biogas production, that is, biochemical methane potential (BMP) has played a prominent role in the choice of substrates, in the other hand the evaluation of the optimal ratio between the quantity of variety OWs and the amount of energy to be produced has not received several attentions. The latter is valuable not only for energetic productivity but also for profitability. Thus, in this report, an energetic balance between the amount of leaves and stems of Manihot Utilissima (MU) annually produced as well as the energetic potential of their biogas were investigated. Cow manure (CM) was employed as inoculum, under mesophilic conditions of the collection sites: Ngaba and Ndjili in Kinshasa City Province (KCP), Congo DR, where the leaves and stems of MU are among the most generated wastes. Furthermore, we evaluated the         fertilizing potential of digestates from the AD of the leaves and stems by their Carbon/Nitrogen (C/N) ratios. The annual energetic potentials of biogas produced were estimated to be 1.362 ± 0.028 109 kWh for the leaves and 0.337 ± 0.006 109 kWh for the stems. These were associated to the energy needs for the KCP households corresponding to the use of charcoal. The latter was evaluated to be 166 103 tons for leaves and 41 103 tons for the stems of MU, respectively. The fertilizing potential of digestates from the AD of the leaves and stems of MU assessed by their C/N ratios were determined to be 5 and 10, respectively; indicating that they are favorable for the cultivation of vegetables and fruit trees in KCP soils (C/N~5) but also optimal for the organisms, soil conditioning and could improve the soils hydraulic conductivity (C/N~10).

Optimal scale production of biogas from the anaerobic digestion (AD) of organic wastes (OWs) as substrates has become one of stimulating environment-friendly procedures to foster the replacement of fossil energies by renewable ones. AD of OWs generated from households is desirable as an effective method to fight against environmental pollution effects of the latter in developing countries. Notably in Africa where each year there are more than 600,000 premature deaths following the use of solid biomass energy (especially charcoal). Yet, if assessing the potential of biogas production, that is, biochemical methane potential (BMP) has played a prominent role in the choice of substrates, in the other hand the evaluation of the optimal ratio between the quantity of variety OWs and the amount of energy to be produced has not received several attentions. The latter is valuable not only for energetic productivity but also for profitability. Thus, in this report, an energetic balance between the amount of leaves and stems of Manihot Utilissima (MU) annually produced as well as the energetic potential of their biogas were investigated. Cow manure (CM) was employed as inoculum, under mesophilic conditions of the collection sites: Ngaba and Ndjili in Kinshasa City Province (KCP), Congo DR, where the leaves and stems of MU are among the most generated wastes. Furthermore, we evaluated the fertilizing potential of digestates from the AD of the leaves and stems by their Carbon/Nitrogen (C/N) ratios. The annual energetic potentials of biogas produced were estimated to be 1.362 ± 0.028 109 kWh for the leaves and 0.337 ± 0.006 109 kWh for the stems. These were associated to the energy needs for the KCP households corresponding to the use of charcoal. The latter was evaluated to be 166 103 tons for leaves and 41 103 tons for the stems of MU, respectively. The fertilizing potential of digestates from the AD of the leaves and stems of MU assessed by their C/N ratios were determined to be 5 and 10, respectively; indicating that they are favorable for the cultivation of vegetables and fruit trees in KCP soils (C/N ~ 5) but also optimal for the organisms, soil conditioning and could improve the soils hydraulic conductivity (C/N ~ 10).