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Solid organic wastes create potential risks to environmental pollution and human health due to the uncontrolled discharge of huge quantities of hazardous wastes from numerous sources. Now-a-days, anaerobic digestion (AD) is considered as a verified and effective alternative compared to other techniques for treating solid organic waste. The paper reviewed the biological process and parameters involved in the AD along with the factors could enhance the AD process. Hydrolysis is considered as a rate-limiting phase in the complex AD process. The performance and stability of AD process is highly influenced by various operating parameters like temperature, pH, carbon and nitrogen ratio, retention time, and organic loading rate. Different pre-treatment (e.g. mechanical, chemical and biological) could enhance the AD process and the biogas yield. Co-digestion can also be used to provide suitable nutrient balance inside the digester. Challenges of the anaerobic digestion for biogas production are also discussed.

The improper management and uncontrolled discharge of huge amounts of food waste have been creating environmental pollution and sanitation-related problems. Anaerobic digestion is considered the most attractive and widely applied technique for the treatment of food waste. This study investigated the effect of feeding mode on the performance of a semi-pilot (160 L) single-stage reactor under different hydraulic retention time (HRT). The reactor was operated under two different feeding modes: daily feeding and feeding 3-times-per-week. Daily feeding mode displayed more stable and efficient performance than feeding mode 3-times-per-week. The maximum biogas yield (1.01 L/g VSadded) and maximum methane yield (0.71 L/g VSadded) in the daily feeding mode at an HRT of 124 ds was higher than that of the feeding mode 3-times-per-week by 11% and 15%, respectively. The accumulation of volatile fatty acid was noticed in both feeding modes, but the accumulation of ammonia was only found in the feeding mode 3-times-per-week. Higher removals of volatile solid (VS) (92.7%) and chemical oxygen demand (COD) (95.84%) were observed for the daily feeding mode at an HRT of 124 ds compared to the feeding mode 3-times-per-week. The removal efficiency of VS and COD during the daily feeding mode increased by 8% and 10%, respectively, compared to the feeding mode 3-times-per-week. Four kinetic models--a first-order-kinetic model, a modified Gompertz model, a logistic function model, and a Cone model--were used to fit the cumulative methane production obtained from the experimental data. The kinetic study indicated that the modified Gompertz model had the best fit (R² = 0.994-0.998) with the experimental data for both feeding modes. [ABSTRACT FROM AUTHOR]