Environmental Research on the Methanogenic Characteristic of Different Chemical States Trace Elements under Laboratory Condition

The problems of energy and the depletion of natural resources have been created with the growing populations and economies. Human are faced with grave challenges like energy pinch and environmental contamination by the existence of these problems. Anaerobic digestion is one of the effective biological organic treatment processes and plays a crucial role in the organic matter stabilization. With the exception of some controllable basic parameters such as temperature, salinity, substrate concentration, pH, pressure and organic loading rate, the concentrations, availability and existing state of trace elements seem to be crucial for the successful operation of biogas plants. In this study, a series of biological gas production experiments that under the same conditions were carried out using three low rank coal samples, which have the approximate degree of metamorphism. ICP-MS and Sequential extraction schemes have been used to detect the modes of occurrence of trace elements in coal. Correlations among the main trace elements occurrence (included Free State, humic acid binding and fulvic acid binding state) and cumulative gas production were also analyzed. The average methane production generated from three samples was 299 (mL), 228 (mL), and 254 (mL), respectively, which existed significant difference in methane yield under the same substrates and conditions. The free ion activity model couldn’t solely explain the differences in average gas production. The anaerobic fermentation system allowed the best state in the methane concentration only when active organic bound state and free state are in a relatively dynamic balance condition. Different biological absorption flux caused by different dispersity result in difference of bioavailability and the bioavailability sequence was: active organic bound state > Free State, humic acid binding state > fulvic acid binding state. There was a poor correction and had obvious differences for A, B, and C coal. These results could be critical not only for environmental information but also provide reference for establish microbial gas production technique based on exogenous nutrition basis.