Plant herbs specifically serai wangi (SW) and peppermint (PPM) are selected for its insect repellent properties as the use of chicken manure (CM) in anaerobic digestion (AD) potentially attract flies due to the digestate produced. Hence, the addition of SW and PPM in the AD system of CM could deter flies\' infestation while producing biogas. Previous work has shown that AD of sawdust (SD) and CM with these plant herbs were able to produce biogas and reduce the flies attraction towards the digestate. However, the combination of SW and PPM for AD of CM has yet to be investigated. This work describes the effect of mixing SW and PPM on the co-AD of SDCM with respect to biogas production, methane yield and kinetic analysis. The mixture of SW and PPM was varied at different concentrations. The composition of methane in biogas was characterized every 10 days by using gas chromatography (GC) equipped with a thermal conductivity detector (TCD). The results suggest that co-AD of 10SW10PPM exhibited the highest biogas production (52.28 mL/gvs) and methane yield (30.89 mL/gvs), which the purity of methane increased by 18.52% as compared to SDCM. However, increasing the concentration of SW and PPM does not significantly improve the overall process. High R2 (0.927-0.999), low RMSE (0.08-0.61) and low prediction error (<10.00%) were displayed by the modified Gompertz, logistic and Cone models. In contrast, Monod and Fitzhugh model is not preferred for the co-AD of SDCM with a mixture of SW and PM, as a high prediction error is obtained throughout the study. Increasing the dosage of PPM decreases the maximum cumulative methane yield, ranging from 31.76 to 7.01 mL/gvs for modified Gompertz and 89.56 to 19.31 mL/gvs for logistic model. The Modified Gompertz obtained a lag phase of 10.01-28.28 days while the logistic model obtained a lag phase of 37.29-52.48 days.

Studies on the production of biogas of different organic materials in an anaerobic environment are being carried out all over the world. The most important parameters in these researches can be listed as raw material potential, production processes, economic analyses, and environmental effects. Chicken manure is one of the raw materials used in biogas production. In this study, in addition to the analysis of biogas and energy production potential from chicken manure, greenhouse gas emissions were analyzed to evaluate environmental effects. In Turkey, chicken manure is not adequately processed and causes environmental pollution. The model biogas plant and potential energy generation were researched in this field study. The pilot plant produces 8.58 million m3 of biogas per year by processing about 110 thousand tons of waste. It produces 17 GWh/year of electricity and 16 GWh/year of thermal energy, as well as reducing CO2 greenhouse gas emissions by 13.86 thousand tons/year.

Increasing popularity and applications of the anaerobic digestion (AD) process has necessitated the development and identification of tools for obtaining reliable indicators of organic matter degradation rate and hence evaluate the process efficiency especially in full-scale, commercial biogas plants. In this study, four biogas plants (A1, A2, B and C) based on different feedstock, process configuration, scale and operational performance were selected and investigated. Results showed that the biochemical methane potential (BMP) based degradation rate could be use in incisively gauging process efficiency in lieu of the traditional degradation rate indicators. The BMP degradation rates ranged from 70 to 90% wherein plants A2 and C showed the highest throughput. This study, therefore, corroborates the feasibility of using the BMP degradation rate as a practical tool for evaluating process performance in full-scale biogas processes and spots light on the microbial diversity in full-scale biogas processes.

The feasibility of co-digestion of chicken manure (CM) and maize silage (MS) without water dilution was investigated in 5-L digesters. Specific methane production (SMP) of 0.309LCH4g(-1) volatile solids (VS) was achieved but only at lower %CM. Above a critical threshold for total ammonia nitrogen (TAN), estimated at 7gNL(-1), VFA accumulated with a characteristic increase in acetic acid followed by its reduction and an increase in propionic acid. During this transition the predominant methanogenic pathway was hydrogenotrophic. Methanogenesis was completely inhibited at TAN of 9gNL(-1). The low digestibility of the mixed feedstock led to a rise in digestate TS and a reduction in SMP over the 297-day experimental period. Methanogenesis appeared to be failing in one digester but was recovered by reducing the %CM. Co-digestion was feasible with CM ⩽20% of feedstock VS, and the main limiting factor was ammonia inhibition.