This paper presents the results of fractionation of particulate and soluble organic matter in a mixture of maize silage and cattle manure (49:51% volatile solids) that was used as a feedstock for anaerobic digestion. The extended Weender’s analysis was adapted to measure raw protein, raw lipids, fraction of carbohydrates (including starch, cellulose, hemicelluloses) and lignin. The content of individual fractions in composite, Xc (as kg COD kg-1 COD) was: 0.111 proteins, 0.048 lipids, 0.500 carbohydrates and 0.341 inerts. The biodegradability of Xc was 68%. Based on material balance, the carbon concentration in Xc was 0.0326 kmol C kg-1 COD, whereas nitrogen concentration 0.0018 kmol N kg-1 COD. The estimated pH of the feedstock based on acid-base equilibrium corresponded to the actual value (pH 7.14).

The aim of this study was to implement ADM1xp model to simulate behavior of anaerobic co-digestion of maize silage and cattle manure. The accuracy of ADM1xp has been assessed against experimental data of anaerobic digestion, performed at OLR = 2.1 gVS dm-3·d-1 and HRT = 45d. Due to the high number of parameters in ADM1xp, it was necessary to develop a customized procedure limiting the range of parameters to be estimated. The best fitting of experimental to simulated data was obtained after verification of 9 among 105 stoichiometric and kinetic parameters. The values of objective function (Jc) ranged between 0.003 (for valerate) and 211 (for biogas production).

In the present study, the removal capacity of Pb(II) ions was investigated using the biomass of dried cattle manure in an aqueous solution. The biomaterials were characterized using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) techniques. The results reveal that the adsorption mechanism may be associated with the interaction between Pb(II) ions and functional groups through aggregation, coordination, ion exchange, microprecipitation, oxidation, and hydrophobicity. The bio-adsorption of the metal was analysed in discontinuous tests; the effect of temperature, pH, agitation, and adsorbent dose was evaluated. The maximum adsorption capacity was determined at pH 7.5, 18°C and 200 rpm. The bio-adsorption of Pb(II) was best fitted to the pseudo-second order model. The experimental data of the isotherm were adjusted to the models of Langmuir, Freundlich and Dubinin–Radushkevich; while Langmuir’s model related better to the experimental data forming a single layer at saturation. The rate of adsorption was rapid, reaching equilibrium after 25 min and removal of 96.8%. Thermodynamic parameters determined that the process was viable, spontaneous, and exothermic. The present study contributes mainly to demonstrating that a biomaterial prepared from bovine manure is a promising adsorbent for heavy metals such as Pb(II). It also reduces the environmental impact of this waste through the generation of greenhouse gases in countries that maintain intensive livestock. Another important aspect is the reduction of the micro- and macronutrients accumulation in soil and contamination of surface waters and aquifers by runoff and seepage during rainy periods.